Risk of Arterial and Venous Thrombotic Events Among Patients with COVID-19: A Multi-National Collaboration of Regulatory Agencies from Canada, Europe, and United States

Purpose

Few studies have examined how the absolute risk of thromboembolism with COVID-19 has evolved over time across different countries. Researchers from the European Medicines Agency, Health Canada, and the United States (US) Food and Drug Administration established a collaboration to evaluate the absolute risk of arterial (ATE) and venous thromboembolism (VTE) in the 90 days after diagnosis of COVID-19 in the ambulatory (eg, outpatient, emergency department, nursing facility) setting from seven countries across North America (Canada, US) and Europe (England, Germany, Italy, Netherlands, and Spain) within periods before and during COVID-19 vaccine availability.

Patients and Methods

We conducted cohort studies of patients initially diagnosed with COVID-19 in the ambulatory setting from the seven specified countries. Patients were followed for 90 days after COVID-19 diagnosis. The primary outcomes were ATE and VTE over 90 days from diagnosis date. We measured country-level estimates of 90-day absolute risk (with 95% confidence intervals) of ATE and VTE.

Results

The seven cohorts included 1,061,565 patients initially diagnosed with COVID-19 in the ambulatory setting before COVID-19 vaccines were available (through November 2020). The 90-day absolute risk of ATE during this period ranged from 0.11% (0.09-0.13%) in Canada to 1.01% (0.97-1.05%) in the US, and the 90-day absolute risk of VTE ranged from 0.23% (0.21-0.26%) in Canada to 0.84% (0.80-0.89%) in England. The seven cohorts included 3,544,062 patients with COVID-19 during vaccine availability (beginning December 2020). The 90-day absolute risk of ATE during this period ranged from 0.06% (0.06-0.07%) in England to 1.04% (1.01-1.06%) in the US, and the 90-day absolute risk of VTE ranged from 0.25% (0.24-0.26%) in England to 1.02% (0.99-1.04%) in the US.

Conclusion

There was heterogeneity by country in 90-day absolute risk of ATE and VTE after ambulatory COVID-19 diagnosis both before and during COVID-19 vaccine availability.

Association between severe acute respiratory syndrome coronavirus 2 antibody status and reinfection: A case-control study nested in a Colorado-based prospective cohort study

The association between the presence of detectable antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and SARS-CoV-2 reinfection is not well established. The objective of this study was to determine the association between antibody seronegativity and reinfection.

METHODS

Participants in Colorado, USA, were recruited between June 15, 2020, and March 28, 2021, and encouraged to complete SARS-CoV-2 molecular ribonucleic acid (RNA) and serology testing for antibodies every 28 days for 10 months. Participants with reinfections (positive SARS-CoV-2 RNA test ≥ 90 days after the first positive RNA test) were matched to controls without reinfections by age, sex, date of the first positive RNA test, date of the last serology test, and serology test type. Using conditional logistic regression, case patients were compared to control patients on the last serologic test result, with adjustment for demographic and clinical confounders.

RESULTS

The cohort (n = 4,235) included 2,033 participants with ≥ 1 positive RNA test, of whom 120 had reinfection. Among the 80 case patients who could be matched, the last serologic test was negative in 12 of the cases (15.0 %) whereas the last serologic test was negative in 77 of 1,034 (7.5 %) controls. Seronegativity (adjusted OR [aOR] 2.24; 95 % CI 1.07, 4.68), Hispanic ethnicity (aOR 1.87; 95 % 1.10, 3.18), and larger household size (aOR 1.15; 95 % 1.01, 1.30 for each additional household member) were associated with reinfection.

CONCLUSIONS

Seronegative status, Hispanic ethnicity, and increasing household size were associated with reinfection. Serologic testing could be considered to reduce vaccine hesitancy in higher risk populations.

Associations between Missed Colonoscopy Appointments and Multiple Prior Adherence Behaviors in an Integrated Healthcare System: An Observational Study

BACKGROUND

Missed colonoscopy appointments delay screening and treatment for gastrointestinal disorders. Prior nonadherence with other care components may be associated with missed colonoscopy appointments.

OBJECTIVE

To assess variability in prior adherence behaviors and their association with missed colonoscopy appointments.

DESIGN

Retrospective cohort study.

PARTICIPANTS

Patients scheduled for colonoscopy in an integrated healthcare system between January 2016 and December 2018.

MAIN MEASURES

Prior adherence behaviors included: any missed outpatient appointment in the previous year; any missed gastroenterology clinic or colonoscopy appointment in the previous 2 years; and not obtaining a bowel preparation kit pre-colonoscopy. Other sociodemographic, clinical, and system characteristics were included in a multivariable model to identify independent associations between prior adherence behaviors and missed colonoscopy appointments.

KEY RESULTS

The median age of the 57,590 participants was 61 years; 52.8% were female and 73.4% were white. Of 77,684 colonoscopy appointments, 3,237 (4.2%) were missed. Individuals who missed colonoscopy appointments were more likely to have missed a previous primary care appointment (62.5% vs. 38.4%), a prior gastroenterology appointment (18.4% vs. 4.7%) or not to have picked up a bowel preparation kit (42.4% vs. 17.2%), all p < 0.001. Correlations between the three adherence measures were weak (phi < 0.26). The rate of missed colonoscopy appointments increased from 1.8/100 among individuals who were adherent with all three prior care components to 24.6/100 among those who were nonadherent with all three care components. All adherence variables remained independently associated with nonadherence with colonoscopy in a multivariable model that included other covariates; adjusted odds ratios (with 95% confidence intervals) were 1.6 (1.5-1.8) for outpatient appointments, 1.9 (1.7-2.1) for gastroenterology appointments, and 3.1 (2.9-3.4) for adherence with bowel preparation kits, respectively.

CONCLUSIONS

Three prior adherence behaviors were independently associated with missed colonoscopy appointments. Studies to predict adherence should use multiple, complementary measures of prior adherence when available.

Risk of admission to hospital with arterial or venous thromboembolism among patients diagnosed in the ambulatory setting with covid-19 compared with influenza: retrospective cohort study

Objective

To measure the 90 day risk of arterial thromboembolism and venous thromboembolism among patients diagnosed with covid-19 in the ambulatory (ie, outpatient, emergency department, or institutional) setting during periods before and during covid-19 vaccine availability and compare results to patients with ambulatory diagnosed influenza.

Design

Retrospective cohort study.

Setting

Four integrated health systems and two national health insurers in the US Food and Drug Administration's Sentinel System.

Participants

Patients with ambulatory diagnosed covid-19 when vaccines were unavailable in the US (period 1, 1 April-30 November 2020; n=272 065) and when vaccines were available in the US (period 2, 1 December 2020-31 May 2021; n=342 103), and patients with ambulatory diagnosed influenza (1 October 2018-30 April 2019; n=118 618).

Main outcome measures

Arterial thromboembolism (hospital diagnosis of acute myocardial infarction or ischemic stroke) and venous thromboembolism (hospital diagnosis of acute deep venous thrombosis or pulmonary embolism) within 90 days after ambulatory covid-19 or influenza diagnosis. We developed propensity scores to account for differences between the cohorts and used weighted Cox regression to estimate adjusted hazard ratios of outcomes with 95% confidence intervals for covid-19 during periods 1 and 2 versus influenza.

Results

90 day absolute risk of arterial thromboembolism with covid-19 was 1.01% (95% confidence interval 0.97% to 1.05%) during period 1, 1.06% (1.03% to 1.10%) during period 2, and with influenza was 0.45% (0.41% to 0.49%). The risk of arterial thromboembolism was higher for patients with covid-19 during period 1 (adjusted hazard ratio 1.53 (95% confidence interval 1.38 to 1.69)) and period 2 (1.69 (1.53 to 1.86)) than for patients with influenza. 90 day absolute risk of venous thromboembolism with covid-19 was 0.73% (0.70% to 0.77%) during period 1, 0.88% (0.84 to 0.91%) during period 2, and with influenza was 0.18% (0.16% to 0.21%). Risk of venous thromboembolism was higher with covid-19 during period 1 (adjusted hazard ratio 2.86 (2.46 to 3.32)) and period 2 (3.56 (3.08 to 4.12)) than with influenza.

Conclusions

Patients diagnosed with covid-19 in the ambulatory setting had a higher 90 day risk of admission to hospital with arterial thromboembolism and venous thromboembolism both before and after covid-19 vaccine availability compared with patients with influenza.

Hypertension care during the COVID-19 pandemic in an integrated health care system

Retention in hypertension care, medication adherence, and blood pressure (BP) may have been affected by the COVID-19 pandemic. In a retrospective cohort study of 64 766 individuals with treated hypertension from an integrated health care system, we compared hypertension care during the year pre-COVID-19 (March 2019-February 2020) and the first year of COVID-19 (March 2020-February 2021). Retention in hypertension care was defined as receiving clinical BP measurements during COVID-19. Medication adherence was measured using prescription refills. Clinical care was assessed by in-person and virtual visits and changes in systolic and diastolic BP. The cohort had a mean age of 67.8 (12.2) years, 51.2% were women, and 73.5% were White. In 60 757 individuals with BP measurements pre-COVID-19, 16618 (27.4%) had no BP measurements during COVID-19. Medication adherence declined from 86.0% to 80.8% (p < .001). In-person primary care visits decreased from 2.7 (2.7) to 1.4 (1.9) per year, while virtual contacts increased from 9.5 (12.2) to 11.2 (14.2) per year (both p < .001). Among individuals with BP measurements, mean (SD) systolic BP was 126.5 mm Hg (11.8) pre-COVID-19 and 127.3 mm Hg (12.6) during COVID-19 (p = .14). Mean diastolic BP was 73.5 mm Hg (8.5) pre-COVID-19 and 73.5 mm Hg (8.7) during COVID-19 (p = .77). Even in this integrated health care system, many individuals did not receive clinical BP monitoring during COVID-19. Most individuals who remained in care maintained pre-COVID BP. Targeted outreach may be necessary to restore care continuity and hypertension control at the population level.

Association of COVID-19 vs Influenza With Risk of Arterial and Venous Thrombotic Events Among Hospitalized Patients

IMPORTANCE

The incidence of arterial thromboembolism and venous thromboembolism in persons with COVID-19 remains unclear.

OBJECTIVE

To measure the 90-day risk of arterial thromboembolism and venous thromboembolism in patients hospitalized with COVID-19 before or during COVID-19 vaccine availability vs patients hospitalized with influenza.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective cohort study of 41 443 patients hospitalized with COVID-19 before vaccine availability (April-November 2020), 44 194 patients hospitalized with COVID-19 during vaccine availability (December 2020-May 2021), and 8269 patients hospitalized with influenza (October 2018-April 2019) in the US Food and Drug Administration Sentinel System (data from 2 national health insurers and 4 regional integrated health systems).

EXPOSURES

COVID-19 or influenza (identified by hospital diagnosis or nucleic acid test).

MAIN OUTCOMES AND MEASURES

Hospital diagnosis of arterial thromboembolism (acute myocardial infarction or ischemic stroke) and venous thromboembolism (deep vein thrombosis or pulmonary embolism) within 90 days. Outcomes were ascertained through July 2019 for patients with influenza and through August 2021 for patients with COVID-19. Propensity scores with fine stratification were developed to account for differences between the influenza and COVID-19 cohorts. Weighted Cox regression was used to estimate the adjusted hazard ratios (HRs) for outcomes during each COVID-19 vaccine availability period vs the influenza period.

RESULTS

A total of 85 637 patients with COVID-19 (mean age, 72 [SD, 13.0] years; 50.5% were male) and 8269 with influenza (mean age, 72 [SD, 13.3] years; 45.0% were male) were included. The 90-day absolute risk of arterial thromboembolism was 14.4% (95% CI, 13.6%-15.2%) in patients with influenza vs 15.8% (95% CI, 15.5%-16.2%) in patients with COVID-19 before vaccine availability (risk difference, 1.4% [95% CI, 1.0%-2.3%]) and 16.3% (95% CI, 16.0%-16.6%) in patients with COVID-19 during vaccine availability (risk difference, 1.9% [95% CI, 1.1%-2.7%]). Compared with patients with influenza, the risk of arterial thromboembolism was not significantly higher among patients with COVID-19 before vaccine availability (adjusted HR, 1.04 [95% CI, 0.97-1.11]) or during vaccine availability (adjusted HR, 1.07 [95% CI, 1.00-1.14]). The 90-day absolute risk of venous thromboembolism was 5.3% (95% CI, 4.9%-5.8%) in patients with influenza vs 9.5% (95% CI, 9.2%-9.7%) in patients with COVID-19 before vaccine availability (risk difference, 4.1% [95% CI, 3.6%-4.7%]) and 10.9% (95% CI, 10.6%-11.1%) in patients with COVID-19 during vaccine availability (risk difference, 5.5% [95% CI, 5.0%-6.1%]). Compared with patients with influenza, the risk of venous thromboembolism was significantly higher among patients with COVID-19 before vaccine availability (adjusted HR, 1.60 [95% CI, 1.43-1.79]) and during vaccine availability (adjusted HR, 1.89 [95% CI, 1.68-2.12]).

CONCLUSIONS AND RELEVANCE

Based on data from a US public health surveillance system, hospitalization with COVID-19 before and during vaccine availability, vs hospitalization with influenza in 2018-2019, was significantly associated with a higher risk of venous thromboembolism within 90 days, but there was no significant difference in the risk of arterial thromboembolism within 90 days.

Pre-Operative Predictors for Discharge to Post-Acute Care Facilities After Total Knee Arthroplasty

BACKGROUND

Joint replacement surgery is in increasing demand and is the most common inpatient surgery for Medicare beneficiaries. The venue for post-operative rehabilitation, including early outpatient therapy after surgery, influences recovery and quality of life. As part of a comprehensive total joint program at Kaiser Permanente Colorado, we developed and validated a predictive model to anticipate and plan the disposition for rehabilitation of our patients after total knee arthroplasty (TKA).

METHODS

We analyzed data for TKA patients who completed a pre-operative Total Knee Risk Assessment in 2017 (the model development cohort) or during the first 6 months of 2018 (the model validation cohort). The Total Knee Risk Assessment, which is used to guide disposition for rehabilitation, included questions in mobility, social, and environment domains. Multivariable logistic regression was used to predict discharge to post-acute care facilities (PACFs) (ie, skilled nursing facilities or acute rehabilitation centers).

RESULTS

Data for a total of 1481 and 631 patients who underwent TKA were analyzed in the development and validation cohorts, respectively. Ninety-three patients (6.3%) in the development cohort and 22 patients (3.5%) in the validation cohort were discharged to PACFs. Eight risk factors for discharge to PACFs were included in the final multivariable model. Patients with a diagnosis of neurological disorder and with a mobility/balance issue had the greatest chance of discharge to PACFs.

CONCLUSION

This validated predictive model for discharge disposition following TKA may be used as a tool in shared decision-making and discharge planning for patients undergoing TKA.

Factors Associated With Opting Out of Automated Text and Telephone Messages Among Adult Members of an Integrated Health Care System

IMPORTANCE

Health care systems deliver automated text or telephone messages to remind patients of appointments and to provide health information. Patients who receive multiple messages may demonstrate message fatigue by opting out of future messages.

OBJECTIVE

To assess whether the volume of automated text or interactive voice response (IVR) telephone messages is associated with the likelihood of patients requesting to opt out of future messages.

DESIGN, SETTING, AND PARTICIPANTS

This retrospective cohort study was conducted at Kaiser Permanente Colorado (KPCO), an integrated health care system. All adult members who received 1 or more automated text or IVR message between October 1, 2018, and September 30, 2019, were included.

EXPOSURES

Receipt of automated text or IVR messages.

MAIN OUTCOMES AND MEASURES

Message volume and opt-out rates obtained from messaging systems over 1 year.

RESULTS

Of the 428 242 adults included in this study, 59.7% were women, and 66.5% were White; the mean (SD) age was 52.3 (17.7) years. During the study period, 84.1% received 1 or more text messages (median, 4 messages; interquartile range, 2-8 messages) and 67.8% received 1 or more IVR messages (median, 3 messages; interquartile range, 1-6 messages). A total of 8929 individuals (2.5%) opted out of text messages, and 4392 (1.5%) opted out of IVR messages. In multivariable analyses, individuals who received 10 to 19.9 or 20 or more text messages per year had higher opt-out rates for text messages compared with those who received fewer than 2 messages per year (adjusted odds ratio [aOR]: 10-19.9 vs <2 messages, 1.27 [95% CI, 1.17-1.38]; ≥20 vs <2 messages, 3.58 [95% CI, 3.28-3.91]), whereas opt-out rates increased progressively in association with IVR message volume, with the highest rates among individuals who received 10.0 to 19.9 messages (aOR, 11.11; 95% CI, 9.43-13.08) or 20.0 messages or more (aOR, 49.84; 95% CI, 42.33-58.70). Individuals opting out of text messages were more likely to opt out of IVR messages (aOR, 4.07; 95% CI, 3.65-4.55), and those opting out of IVR messages were more likely to opt out of text messages (aOR, 5.92; 95% CI, 5.29-6.61).

CONCLUSIONS AND RELEVANCE

In this cohort study among adult members of an integrated health care system, requests to discontinue messages were associated with greater message volume. These findings suggest that, to preserve the benefits of automated outreach, health care systems should use these messages judiciously to reduce message fatigue.

Development and Validation of a Model for Predicting Rehabilitation Care Location Among Patients Discharged Home After Total Knee Arthroplasty

BACKGROUND

Demand for joint replacement is increasing, with many patients receiving postsurgical physical therapy (PT) in non-inpatient settings. Clinicians need a reliable tool to guide decisions about the appropriate PT setting for patients discharged home after surgery. We developed and validated a model to predict PT location for patients in our health system discharged home after total knee arthroplasty.

METHODS

We analyzed data for patients who completed a preoperative total knee risk assessment in 2017 (model development cohort) or during the first 6 months of 2018 (model validation cohort). The initial total knee risk assessment, to guide rehabilitation disposition, included 28 variables in mobility, social, and environment domains, and on patient demographics and comorbidities. Multivariable logistic regression was used to identify factors that best predict discharge to home health service (HHS) vs home with outpatient PT. Model performance was assessed by standard criteria.

RESULTS

The development cohort included 259 patients (19%) discharged to HHS and 1129 patients (81%) discharged to home with outpatient PT. The validation cohort included 609 patients, with 91 (15%) discharged to HHS. The final model included age, gender, motivation for outpatient PT, and reliable transportation. Patients without motivation for outpatient PT had the highest probability of discharge to HHS, followed by those without reliable transportation. Model performance was excellent in the development and validation cohort, with c-statistics of 0.91 and 0.86, respectively.

CONCLUSION

We developed and validated a predictive model for total knee arthroplasty PT discharge location. This model includes 4 variables with accurate prediction to guide patient-clinician preoperative decision making.

Longer-term Direct and Indirect Effects of Infant Rotavirus Vaccination Across All Ages in the United States in 2000-2013: Analysis of a Large Hospital Discharge Data Set

BACKGROUND

Rotavirus disease rates dramatically declined among children <5 years of age since the rotavirus vaccine was introduced in 2006; population-level impacts remain to be fully elucidated.

METHODS

Data from the Healthcare Cost and Utilization Project State Inpatient Databases were used to conduct a time-series analysis of monthly hospital discharges across age groups for acute gastroenteritis and rotavirus from 2000 to 2013. Rate ratios were calculated comparing prevaccine and postvaccine eras.

RESULTS

Following vaccine introduction, a decrease in rotavirus hospitalizations occurred with a shift toward biennial patterns across all ages. The 0-4-year age group experienced the largest decrease in rotavirus hospitalizations (rate ratio, 0.14; 95% confidence interval, .09-.23). The 5-19-year and 20-59-year age groups experienced significant declines in rotavirus hospitalization rates overall; the even postvaccine calendar years were characterized by progressively lower rates, and the odd postvaccine years were associated with reductions in rates that diminished over time. Those aged ≥60 years experienced the smallest change in rotavirus hospitalization rates overall, with significant reductions in even postvaccine years compared with prevaccine years (rate ratio, 0.51; 95% confidence interval, .39-.66).

CONCLUSIONS

Indirect impacts of infant rotavirus vaccination are apparent in the emergence of biennial patterns in rotavirus hospitalizations that extend to all age groups ineligible for vaccination. These observations are consistent with the notion that young children are of primary importance in disease transmission and that the initial postvaccine period of dramatic population-wide impacts will be followed by more complex incidence patterns across the age range in the long term.

Hospitalizations Associated with Respiratory Syncytial Virus and Influenza in Children, Including Children Diagnosed with Asthma

BACKGROUND

There is uncertainty about the burden of hospitalization associated with respiratory syncytial virus (RSV) and influenza in children, including those with underlying medical conditions.

METHODS

We applied previously developed methodology to Health Care Cost and Utilization Project hospitalization data and additional data related to asthma diagnosis/previous history in hospitalized children to estimate RSV and influenza-associated hospitalization rates in different subpopulations of US children between 2003 and 2010.

RESULTS

The estimated average annual rates (per 100,000 children) of RSV-associated hospitalization with a respiratory cause (ICD-9 codes 460-519) present anywhere in the discharge diagnosis were 2,381 (95% CI(2252,2515)) in children <1 year of age; 710.6 (609.1, 809.2) (1 y old); 395 (327.7, 462.4) (2 y old); 211.3 (154.6, 266.8) (3 y old); 111.1 (62.4, 160.1) (4 y old); 72.3 (29.3, 116.4) (5-6 y of age); 35.6 (9.9,62.2) (7-11 y of age); and 39 (17.5, 60.6) (12-17 y of age). The corresponding rates of influenza-associated hospitalization were lower, ranging from 181 (142.5, 220.3) in <1 year old to 17.9 (11.7, 24.2) in 12-17 years of age. The relative risks for RSV-related hospitalization associated with a prior diagnosis of asthma in age groups <5 y ranged between 3.1 (2.1, 4.7) (<1 y old) and 6.7 (4.2, 11.8) (2 y old; the corresponding risks for influenza-related hospitalization ranged from 2.8 (2.1, 4) (<1y old) to 4.9 (3.8, 6.4) (3 y old).

CONCLUSION

RSV-associated hospitalization rates in young children are high and decline rapidly with age. There are additional risks for both RSV and influenza hospitalization associated with a prior diagnosis of asthma, with the rates of RSV-related hospitalization in the youngest children diagnosed with asthma being particularly high.

Levels of outpatient prescribing for four major antibiotic classes and rates of septicemia hospitalization in adults in different US states - a statistical analysis

BACKGROUND

Rates of sepsis/septicemia hospitalization in the US have risen significantly during recent years. Antibiotic resistance and use may contribute to those rates through various mechanisms, including lack of clearance of resistant infections following antibiotic treatment, with some of those infections subsequently devolving into sepsis. At the same time, there is limited information on the effect of prescribing of certain antibiotics vs. others on the rates of septicemia and sepsis-related hospitalizations and mortality.

METHODS

We used multivariable linear regression to relate state-specific rates of outpatient prescribing overall for oral fluoroquinolones, penicillins, macrolides, and cephalosporins between 2011 and 2012 to state-specific rates of septicemia hospitalization (ICD-9 codes 038.xx present anywhere on a discharge diagnosis) in each of the following age groups of adults: (18-49y, 50-64y, 65-74y, 75-84y, 85 + y) reported to the Healthcare Cost and Utilization Project (HCUP) between 2011 and 2012, adjusting for additional covariates, and random effects associated with the ten US Health and Human Services (HHS) regions.

RESULTS

Increase in the rate of prescribing of oral penicillins by 1 annual dose per 1000 state residents was associated with increases in annual septicemia hospitalization rates of 0.19 (95% CI (0.02,0.37)) per 10,000 persons aged 50-64y, of 0.48(0.12,0.84) per 10,000 persons aged 65-74y, and of 0.81(0.17,1.40) per 10,000 persons aged 74-84y. Increase by 1 in the percent of African Americans among state residents in a given age group was associated with increases in annual septicemia hospitalization rates of 2.3(0.32,4.2) per 10,000 persons aged 75-84y, and of 5.3(1.1,9.5) per 10,000 persons aged over 85y. Average minimal daily temperature was positively associated with septicemia hospitalization rates in persons aged 18-49y, 50-64y, 75-84y and over 85y.

CONCLUSIONS

Our results suggest positive associations between the rates of prescribing for penicillins and the rates of hospitalization with septicemia in US adults aged 50-84y. Further studies are needed to better understand the potential effect of antibiotic replacement in the treatment of various syndromes, including the potential impact of the recent US FDA guidelines on restriction of fluoroquinolone use, as well as the potential effect of changes in the practices for prescribing of penicillins on the rates of sepsis-related hospitalization and mortality.

Antimicrobial resistance prevalence, rates of hospitalization with septicemia and rates of mortality with sepsis in adults in different US states

OBJECTIVES

Rates of hospitalization with sepsis/septicemia and associated mortality in the US have risen significantly during the last two decades. Antibiotic resistance may contribute to the rates of sepsis-related outcomes through lack of clearance of bacterial infections following antibiotic treatment during different stages of infection. However, there is limited information about the relationship between prevalence of resistance to various antibiotics in different bacteria and rates of sepsis-related outcomes.

METHODS

For different age groups of adults (18-49y, 50-64y, 65-74y, 75-84y, 85+y) and combinations of antibiotics/bacteria, we evaluated associations between state-specific prevalence (percentage) of resistant samples for a given combination of antibiotics/bacteria among catheter-associated urinary tract infections (CAUTIs) in the CDC Antibiotic Resistance Patient Safety Atlas data between 2011-2014, and rates of hospitalization with septicemia (ICD-9 codes 038.xx present on the discharge diagnosis) reported to the Healthcare Cost and Utilization Project (HCUP), as well as rates of mortality with sepsis (ICD-10 codes A40-41.xx present on death certificate).

RESULTS

Among the different combinations of antibiotics/bacteria, prevalence of resistance to fluoroquinolones in Escherichia coli had the strongest association with septicemia hospitalization rates for individuals aged over 50y, and with sepsis mortality rates for individuals aged 18-84y. There were several positive correlations between prevalence of resistance for different combinations of antibiotics/bacteria and septicemia hospitalization/sepsis mortality rates in adults.

CONCLUSIONS

These findings, and those from work on the relationship between antibiotic use and sepsis rates, support the association between use of/resistance to certain antibiotics and rates of sepsis-related outcomes, indicating the potential utility of antibiotic replacement.

Trends in Rate of Seizure-Associated Hospitalizations Among Children <5 Years Old Before and After Rotavirus Vaccine Introduction in the United Sates, 2000-2013

Background

Rotavirus is a common cause of acute gastroenteritis and has also been associated with generalized tonic-clonic afebrile seizures. Since rotavirus vaccine introduction, hospitalizations for treatment of acute gastroenteritis have decreased. We assess whether there has been an associated decrease in seizure-associated hospitalizations.

Methods

We used discharge codes to abstract data on seizure hospitalizations among children <5 years old from the State Inpatient Databases of the Healthcare Cost and Utilization Project. We compared seizure hospitalization rates before and after vaccine introduction, using Poisson regression, stratifying by age and by month and year of admission. We performed a time-series analysis with negative binomial models, constructed using prevaccine data from 2000 to 2006 and controlling for admission month and year.

Results

We examined 962899 seizure hospitalizations among children <5 years old during 2000-2013. Seizure rates after vaccine introduction were lower than those before vaccine introduction by 1%-8%, and rate ratios decreased over time. Time-series analyses demonstrated a decrease in the number of seizure-coded hospitalizations in 2012 and 2013, with notable decreases in children 12-17 months and 18-23 months.

Conclusions

Our analysis provides evidence for a decrease in seizure hospitalizations following rotavirus vaccine introduction in the United States, with the greatest impact in age groups with a high rotavirus-associated disease burden and during rotavirus infection season.

On the Relative Role of Different Age Groups During Epidemics Associated With Respiratory Syncytial Virus

Background

While circulation of respiratory syncytial virus (RSV) results in high rates of hospitalization, particularly among young children and elderly individuals, little is known about the role of different age groups in propagating annual RSV epidemics.

Methods

We evaluate the roles played by individuals in different age groups during RSV epidemics in the United States between 2001 and 2012, using the previously defined relative risk (RR) statistic estimated from the hospitalization data from the Healthcare Cost and Utilization Project. Transmission modeling was used to examine the robustness of our inference method.

Results

Children aged 3-4 years and 5-6 years each had the highest RR estimate for 5 of 11 seasons included in this study, with RSV hospitalization rates in infants being generally higher during seasons when children aged 5-6 years had the highest RR estimate. Children aged 2 years had the highest RR estimate during one season. RR estimates in infants and individuals aged ≥11 years were mostly lower than in children aged 1-10 years. Highest RR values aligned with groups for which vaccination had the largest impact on epidemic dynamics in most model simulations.

Conclusions

Our estimates suggest the prominent relative roles of children aged ≤10 years (particularly among those aged 3-6 years) in propagating RSV epidemics. These results, combined with further modeling work, should help inform RSV vaccination policies.

National Estimates of Reductions in Acute Gastroenteritis-Related Hospitalizations and Associated Costs in US Children After Implementation of Rotavirus Vaccines

We compared acute gastroenteritis (AGE)-related hospitalization rates among children <5 years of age during the pre-rotavirus vaccine (2000-2006) and post-rotavirus vaccine (2008-2013) periods to estimate national reductions in AGE-related hospitalizations and associated costs. We estimate that between 2008 and 2013, AGE-related hospitalizations declined by 382000, and $1.228 billion in medical costs were averted.

Mandatory Physician Reporting of At-Risk Drivers: The Older Driver Example

Purpose of the Study

In a number of states, physicians are mandated by state law to report at-risk drivers to licensing authorities. Often these patients are older adult drivers who may exhibit unsafe driving behaviors, have functional/cognitive impairments, or are diagnosed with conditions such as Alzheimer's disease and/or seizure disorders. The hypothesis that mandatory physician reporting laws reduce the rate of crash-related hospitalizations among older adult drivers was tested.

Design and Methods

Using retrospective data (2004-2009), this study identified 176,066 older driver crash-related hospitalizations, from the State Inpatient Databases. Three age-specific negative binomial generalized estimating equation models were used to estimate the effect of physician reporting laws on state's incidence rate of crash-related hospitalizations among older drivers.

Results

No evidence was found for an independent association between mandatory physician reporting laws and a lower crash hospitalization rate among any of the age groups examined. The main predictor of interest, mandatory physician reporting, failed to explain any significant variation in crash hospitalization rates, when adjusting for other state-specific laws and characteristics. Vision testing at in-person license renewal was a significant predictor of lower crash hospitalization rate, ranging from incidence rate ratio of 0.77 (95% confidence interval 0.62-0.94) among 60- to 64-year olds to 0.83 (95% confidence interval 0.67-0.97) among 80- to 84-year olds.

Implications

Physician reporting laws and age-based licensing requirements are often at odds with older driver's need to maintain independence. This study examines this balance and finds no evidence of the benefits of mandatory physician reporting requirements on driver crash hospitalizations, suggesting that physician mandates do not yet yield significant older driver safety benefits, possibly to the detriment of older driver's well-being and independence.

Returns to Emergency Department, Observation, or Inpatient Care Within 30 Days After Hospitalization in 4 States, 2009 and 2010 Versus 2013 and 2014

BACKGROUND

Nationally, readmissions have declined for acute myocardial infarction (AMI) and heart failure (HF) and risen slightly for pneumonia, but less is known about returns to the hospital for observation stays and emergency department (ED) visits.

OBJECTIVE

To describe trends in rates of 30-day, all-cause, unplanned returns to the hospital, including returns for observation stays and ED visits.

DESIGN

By using Healthcare Cost and Utilization Project data, we compared 210,007 index hospitalizations in 2009 and 2010 with 212,833 matched hospitalizations in 2013 and 2014.

SETTING

Two hundred and one hospitals in Georgia, Nebraska, South Carolina, and Tennessee.

PATIENTS

Adults with private insurance, Medicaid, or no insurance and seniors with Medicare who were hospitalized for AMI, HF, and pneumonia.

MEASUREMENTS

Thirty-day hospital return rates for inpatient, observation, and ED visits.

RESULTS

Return rates remained stable among adults with private insurance (15.1% vs 15.3%; P = 0.45) and declined modestly among seniors with Medicare (25.3% vs 25.0%; P = 0.04). Increases in observation and ED visits coincided with declines in readmissions (8.9% vs 8.2% for private insurance and 18.3% vs 16.9% for Medicare, both P ≤ 0.001). Return rates rose among patients with Medicaid (31.0% vs 32.1%; P = 0.04) and the uninsured (18.8% vs 20.1%; P = 0.004). Readmissions remained stable (18.7% for Medicaid and 9.5% for uninsured patients, both P > 0.75) while observation and ED visits increased.

CONCLUSIONS

Total returns to the hospital are stable or rising, likely because of growth in observation and ED visits. Hospitalists' efforts to improve the quality and value of hospital care should consider observation and ED care.

Dementia and motor vehicle crash hospitalizations: Role of physician reporting laws

OBJECTIVE

To determine the effect of physician reporting laws and state licensing requirements on crash hospitalizations among drivers with dementia.

METHODS

A study of drivers hospitalized because of vehicle crashes, identified from the State Inpatient Databases of the Agency for Healthcare Research and Quality. Multivariable logistic regression was used to examine the effect of mandatory physician reporting of at-risk drivers and state licensing requirement on the prevalence of dementia among hospitalized drivers.

RESULTS

Physician reporting laws, mandated or legally protected, were not associated with a lower likelihood of dementia among crash hospitalized drivers. Hospitalized drivers aged 60 to 69 years in states with in-person renewal laws were 37% to 38% less likely to have dementia than drivers in other states and 23% to 28% less likely in states with vision testing at in-person renewal. Road testing was associated with lower dementia prevalence among hospitalized drivers aged 80 years and older.

CONCLUSION

Vision testing at in-person renewal and in-person renewal requirements were significantly related with a lower prevalence of dementia in hospitalized older adults among drivers aged 60 to 69 years. Road testing was significantly associated with a lower proportion of dementia among hospitalized drivers aged 80 years and older. Mandatory physician driver reporting laws lacked any independent association with prevalence of dementia among hospitalized drivers.

Use of Internet Search Data to Monitor Rotavirus Vaccine Impact in the United States, United Kingdom, and Mexico

BACKGROUND

Previous studies have found a strong correlation between internet search and public health surveillance data. Less is known about how search data respond to public health interventions, such as vaccination, and the consistency of responses in different countries. In this study, we aimed to study the correlation between internet searches for "rotavirus" and rotavirus disease activity in the United States, United Kingdom, and Mexico before and after introduction of rotavirus vaccine.

METHODS

We compared time series of internet searches for "rotavirus" from Google Trends with rotavirus laboratory reports from the United States and United Kingdom and with hospitalizations for acute gastroenteritis in the United States and Mexico. Using time and location parameters, Google quantifies an internet query share (IQS) to measure the relative search volume for specific terms. We analyzed the correlation between IQS and laboratory and hospitalization data before and after national vaccine introductions.

RESULTS

There was a strong positive correlation between the rotavirus IQS and laboratory reports in the United States (R2 = 0.79) and United Kingdom (R2 = 0.60) and between the rotavirus IQS and acute gastroenteritis hospitalizations in the United States (R2 = 0.87) and Mexico (R2 = 0.69) (P < .0001 for all correlations). The correlations were stronger in the prevaccine period than in the postvaccine period. After vaccine introduction, the mean rotavirus IQS decreased by 40% (95% confidence interval [CI], 25%-55%) in the United States and by 70% (95% CI, 55%-86%) in Mexico. In the United Kingdom, there was a loss of seasonal variation after vaccine introduction.

CONCLUSIONS

Rotavirus internet search data trends mirrored national rotavirus laboratory trends in the United States and United Kingdom and gastroenteritis-hospitalization data in the United States and Mexico; lower correlations were found after rotavirus vaccine introduction.

Epidemiology of Hospitalizations Associated with Invasive Candidiasis, United States, 2002-20121

Highest hospitalization rates were for men ≥65 years of age, and rates decreased during 2005−2012.

Invasive candidiasis is a major nosocomial fungal disease in the United States associated with high rates of illness and death. We analyzed inpatient hospitalization records from the Healthcare Cost and Utilization Project to estimate incidence of invasive candidiasis–associated hospitalizations in the United States. We extracted data for 33 states for 2002–2012 by using codes from the International Classification of Diseases, 9th Revision, Clinical Modification, for invasive candidiasis; we excluded neonatal cases. The overall age-adjusted average annual rate was 5.3 hospitalizations/100,000 population. Highest risk was for adults >65 years of age, particularly men. Median length of hospitalization was 21 days; 22% of patients died during hospitalization. Median unadjusted associated cost for inpatient care was $46,684. Age-adjusted annual rates decreased during 2005–2012 for men (annual change –3.9%) and women (annual change –4.5%) and across nearly all age groups. We report a high mortality rate and decreasing incidence of hospitalizations for this disease.

A Nationwide Assessment of the Association of Smoking Bans and Cigarette Taxes With Hospitalizations for Acute Myocardial Infarction, Heart Failure, and Pneumonia

Multiple studies claim that public place smoking bans are associated with reductions in smoking-related hospitalization rates. No national study using complete hospitalization counts by area that accounts for contemporaneous controls including state cigarette taxes has been conducted. We examine the association between county-level smoking-related hospitalization rates and comprehensive smoking bans in 28 states from 2001 to 2008. Differences-in-differences analysis measures changes in hospitalization rates before versus after introducing bans in bars, restaurants, and workplaces, controlling for cigarette taxes, adjusting for local health and provider characteristics. Smoking bans were not associated with acute myocardial infarction or heart failure hospitalizations, but lowered pneumonia hospitalization rates for persons ages 60 to 74 years. Higher cigarette taxes were associated with lower heart failure hospitalizations for all ages and fewer pneumonia hospitalizations for adults aged 60 to 74. Previous studies may have overestimated the relation between smoking bans and hospitalizations and underestimated the effects of cigarette taxes.

The Shifting Landscape in Utilization of Inpatient, Observation, and Emergency Department Services Across Payers

Recent policies by public and private payers have increased incentives to reduce hospital admissions. Using data from four states from the Agency for Healthcare Research and Quality Healthcare Cost and Utilization Project, this study compared the payer-specific population-based rates of adults using inpatient, observation, and emergency department (ED) services for 10 common medical conditions in 2009 and in 2013. Patients had an expected primary payer of private insurance, Medicare, Medicaid, or no insurance. Across all four payer populations, inpatient admissions declined, and care shifted toward treat-and-release observation stays and ED visits. The percentage of hospitalizations that began with an observation stay increased. Implications for quality of care and costs to patients warrant further examination. Journal of Hospital Medicine 2017;12:443-446.

Million Hearts: Description of the National Surveillance and Modeling Methodology Used to Monitor the Number of Cardiovascular Events Prevented During 2012-2016

Background

This study describes the national surveillance and modeling methodology developed to monitor achievement of the Million Hearts initiative's aim of preventing 1 million acute myocardial infarctions, strokes, and other related cardiovascular events during 2012–2016.

Methods and Results

We calculate sex‐ and age‐specific cardiovascular event rates (combination of emergency department, hospitalization, and death events) among US adults aged ≥18 from 2006 to 2011 and, based on log‐linear models fitted to the rates, calculate their annual percent change. We describe 2 baseline strategies to be used to compare observed versus expected event totals during 2012–2016: (1) stable baselines assume no rate changes, with modeled 2011 rates held constant through 2016; and (2) trend baselines assume 2006–2011 rate trends will continue, with the annual percent changes applied to the modeled 2011 rates to calculate expected 2012–2016 rates. Events prevented estimates during 2012–2013 were calculated using available data: 115 210 (95% CI, 60 858, 169 562) events were prevented using stable baselines and an excess of 43 934 (95% CI, −14 264, 102 132) events occurred using trend baselines. Women aged ≥75 had the most events prevented (stable, 76 242 [42 067, 110 417]; trend, 39 049 [1901, 76 197]). Men aged 45 to 64 had the greatest number of excess events (stable, 22 912 [95% CI, 855, 44 969]; trend, 38 810 [95% CI, 15 567, 62 053]).

Conclusions

Around 115 000 events were prevented during the initiative's first 2 years compared with what would have occurred had 2011 rates remained stable. Recent flattening or reversals in some event rate trends were observed supporting intensifying national action to prevent cardiovascular events.

Identifying in-patient costs attributable to the clinical sequelae and comorbidities of alcoholic liver disease in a national hospital database

BACKGROUND AND AIMS

The clinical sequelae and comorbidities of alcoholic liver disease (ALD) often require hospitalization. The aims of this study were to (1) compare the average costs of hospitalizations with ALD and the costs of hospitalizations with other alcohol-related diagnoses that do not involve the liver; and (2) estimate the percentage of the difference in costs between the ALD and non-ALD hospitalizations that may be attributed to ascites, protein-calorie malnutrition and other conditions.

DESIGN

The 2012 National Inpatient Sample is a population-based cross-sectional database representing more than 94% of all discharges from community hospitals in the United States.

SETTING

Community hospitals in the United States.

PARTICIPANTS

The sample included 72 531 hospitalizations with ALD and 287 047 hospitalizations with other alcohol-related diagnoses.

MEASUREMENTS

The dependent variable was total in-patient costs. We estimated the contribution of ascites, protein-calorie malnutrition and other conditions to the difference in costs between patients with ALD and patients with other diagnoses.

FINDINGS

Average costs for ALD patients were $3188.4 higher than those for patients with other diagnoses ($13 543 versus $10 355; P < 0.001). Among all conditions in the analysis, protein-calorie malnutrition had the largest impact on costs [$6501; 95% confidence interval (CI) = 5956, 7045; P < 0.001] accounting for 12% of the higher costs of ALD stays.

CONCLUSIONS

Costs of hospital care for patients with alcoholic liver disease are higher than those for patients with other alcohol-related diagnoses. These increased costs are associated with specific clinical sequelae and comorbidities, with protein-calorie malnutrition-a largely preventable condition-making a substantial contribution.

Infectious Disease Hospitalizations Among American Indian/Alaska Native and Non-American Indian/Alaska Native Persons in Alaska, 2010-2011

OBJECTIVE

Reports about infectious disease (ID) hospitalization rates among American Indian/Alaska Native (AI/AN) persons have been constrained by data limited to the tribal health care system and by comparisons with the general US population. We used a merged state database to determine ID hospitalization rates in Alaska.

METHODS

We combined 2010 and 2011 hospital discharge data from the Indian Health Service and the Alaska State Inpatient Database. We used the merged data set to calculate average annual age-adjusted and age-specific ID hospitalization rates for AI/AN and non-AI/AN persons in Alaska. We stratified the ID hospitalization rates by sex, age, and ID diagnosis.

RESULTS

ID diagnoses accounted for 19% (6501 of 34 160) of AI/AN hospitalizations, compared with 12% (7397 of 62 059) of non-AI/AN hospitalizations. The average annual age-adjusted hospitalization rate was >3 times higher for AI/AN persons (2697 per 100 000 population) than for non-AI/AN persons (730 per 100 000 population; rate ratio = 3.7, P < .001). Lower respiratory tract infection (LRTI), which occurred in 38% (2486 of 6501) of AI/AN persons, was the most common reason for ID hospitalization. AI/AN persons were significantly more likely than non-AI/AN persons to be hospitalized for LRTI (rate ratio = 5.2, P < .001).

CONCLUSIONS

A substantial disparity in ID hospitalization rates exists between AI/AN and non-AI/AN persons, and the most common reason for ID hospitalization among AI/AN persons was LRTI. Public health programs and policies that address the risk factors for LRTI are likely to benefit AI/AN persons.

Intussusception Rates Before and After the Introduction of Rotavirus Vaccine

BACKGROUND

Recent US studies have identified a small increased risk of intussusception after rotavirus vaccination, mainly after the first dose. We examined trends in intussusception hospitalizations before (2000-2005) and after (2007-2013) rotavirus vaccine introduction to assess whether this observed temporal risk translates into more hospitalized cases at the population level.

METHODS

Intussusception hospitalizations in children <12 months of age were abstracted from the State Inpatient Database maintained by the Healthcare Cost and Utilization Project for 26 states that provided data from 2000 to 2013. Rates were calculated using bridged-race postcensal population estimates. Trends were analyzed by age groups (6-14 weeks, 15-24 weeks, and 25-34 weeks) based on the recommended ages for vaccine administration as well as 8-11 weeks when the majority of first doses are given. Rate ratios were calculated by using Poisson regression.

RESULTS

No consistent change in intussusception hospitalization rates was observed among all children <12 months of age and among children 15 to 24 weeks and 25 to 34 weeks of age. The intussusception hospitalization rate for children aged 8 to 11 weeks was significantly elevated by 46% to 101% (range: 16.7-22.9 per 100 000) in all postvaccine years except 2011 and 2013 compared with the prevaccine baseline (11.7 per 100 000).

CONCLUSIONS

The increase in the intussusception hospitalization rate in children 8 to 11 weeks when the majority of first doses of vaccine are given is consistent with recent US postlicensure studies. Given the magnitude of declines in rotavirus disease compared with this small increase in intussusception, the benefits of rotavirus vaccination outweigh the increase risk of intussusception.

Impact of Race/Ethnicity and Socioeconomic Status on Risk-Adjusted Hospital Readmission Rates Following Hip and Knee Arthroplasty

BACKGROUND

Readmission rates following total hip arthroplasty (THA) and total knee arthroplasty (TKA) are increasingly used to measure hospital performance. Readmission rates that are not adjusted for race/ethnicity and socioeconomic status, patient risk factors beyond a hospital's control, may not accurately reflect a hospital's performance. In this study, we examined the extent to which risk-adjusting for race/ethnicity and socioeconomic status affected hospital performance in terms of readmission rates following THA and TKA.

METHODS

We calculated 2 sets of risk-adjusted readmission rates by (1) using the Centers for Medicare & Medicaid Services standard risk-adjustment algorithm that incorporates patient age, sex, comorbidities, and hospital effects and (2) adding race/ethnicity and socioeconomic status to the model. Using data from the Healthcare Cost and Utilization Project, 2011 State Inpatient Databases, we compared the relative performances of 1,194 hospitals across the 2 methods.

RESULTS

Addition of race/ethnicity and socioeconomic status to the risk-adjustment algorithm resulted in (1) little or no change in the risk-adjusted readmission rates at nearly all hospitals; (2) no change in the designation of the readmission rate as better, worse, or not different from the population mean at >99% of the hospitals; and (3) no change in the excess readmission ratio at >97% of the hospitals.

CONCLUSIONS

Inclusion of race/ethnicity and socioeconomic status in the risk-adjustment algorithm led to a relative-performance change in readmission rates following THA and TKA at <3% of the hospitals. We believe that policymakers and payers should consider this result when deciding whether to include race/ethnicity and socioeconomic status in risk-adjusted THA and TKA readmission rates used for hospital accountability, payment, and public reporting.

LEVEL OF EVIDENCE

Prognostic Level III. See instructions for Authors for a complete description of levels of evidence.

Towards valid 'serious non-fatal injury' indicators for international comparisons based on probability of admission estimates

BACKGROUND

Governments wish to compare their performance in preventing serious injury. International comparisons based on hospital inpatient records are typically contaminated by variations in health services utilisation. To reduce these effects, a serious injury case definition has been proposed based on diagnoses with a high probability of inpatient admission (PrA). The aim of this paper was to identify diagnoses with estimated high PrA for selected developed countries.

METHODS

The study population was injured persons of all ages who attended emergency department (ED) for their injury in regions of Canada, Denmark, Greece, Spain and the USA. International Classification of Diseases (ICD)-9 or ICD-10 4-digit/character injury diagnosis-specific ED attendance and inpatient admission counts were provided, based on a common protocol. Diagnosis-specific and region-specific PrAs with 95% CIs were calculated.

RESULTS

The results confirmed that femoral fractures have high PrA across all countries studied. Strong evidence for high PrA also exists for fracture of base of skull with cerebral laceration and contusion; intracranial haemorrhage; open fracture of radius, ulna, tibia and fibula; pneumohaemothorax and injury to the liver and spleen. Slightly weaker evidence exists for cerebellar or brain stem laceration; closed fracture of the tibia and fibula; open and closed fracture of the ankle; haemothorax and injury to the heart and lung.

CONCLUSIONS

Using a large study size, we identified injury diagnoses with high estimated PrAs. These diagnoses can be used as the basis for more valid international comparisons of life-threatening injury, based on hospital discharge data, for countries with well-developed healthcare and data collection systems.

Differences in severity at admission for heart failure between rural and urban patients: the value of adding laboratory results to administrative data

BACKGROUND

Rural/urban variations in admissions for heart failure may be influenced by severity at hospital presentation and local practice patterns. Laboratory data reflect clinical severity and guide hospital admission decisions and treatment for heart failure, a costly chronic illness and a leading cause of hospitalization among the elderly. Our main objective was to examine the role of laboratory test results in measuring disease severity at the time of admission for inpatients who reside in rural and urban areas.

METHODS

We retrospectively analyzed discharge data on 13,998 hospital discharges for heart failure from three states, Hawai'i, Minnesota, and Virginia. Hospital discharge records from 2008 to 2012 were derived from the State Inpatient Databases of the Healthcare Cost and Utilization Project, and were merged with results of laboratory tests performed on the admission day or up to two days before admission. Regression models evaluated the relationship between clinical severity at admission and patient urban/rural residence. Models were estimated with and without use of laboratory data.

RESULTS

Patients residing in rural areas were more likely to have missing laboratory data on admission and less likely to have abnormal or severely abnormal tests. Rural patients were also less likely to be admitted with high levels of severity as measured by the All Patient Refined Diagnosis Related Groups (APR-DRG) severity subclass, derivable from discharge data. Adding laboratory data to discharge data improved model fit. Also, in models without laboratory data, the association between urban compared to rural residence and APR-DRG severity subclass was significant for major and extreme levels of severity (OR 1.22, 95% CI 1.03-1.43 and 1.55, 95% CI 1.26-1.92, respectively). After adding laboratory data, this association became non-significant for major severity and was attenuated for extreme severity (OR 1.12, 95% CI 0.94-1.32 and 1.43, 95% CI 1.15-1.78, respectively).

CONCLUSION

Heart failure patients from rural areas are hospitalized at lower severity levels than their urban counterparts. Laboratory test data provide insight on clinical severity and practice patterns beyond what is available in administrative discharge data.

Potentially preventable hospitalizations for acute and chronic conditions in Alaska, 2010-2012

OBJECTIVE

The U.S. Agency for Healthcare Research and Quality's Prevention Quality Indicators comprise acute and chronic conditions for which hospitalization can be potentially prevented by high-quality ambulatory care. The Healthy Alaska 2020 initiative (HA2020) targeted reducing potentially preventable hospitalizations (PPH) for acute and chronic conditions among its health indicators. We estimated the PPH rate for adults aged ≥ 18 years in Alaska during 2010-2012.

METHODS

We conducted a cross-sectional analysis of state-wide hospital discharge data obtained from the Healthcare Cost and Utilization Project and the Indian Health Service. We calculated average annual PPH rates/1000 persons for acute/chronic conditions. Age-adjusted rate ratios (aRRs) were used for evaluating PPH rate disparities between Alaska Native (AN) and non-AN adults.

RESULTS

Among 127,371 total hospitalizations, 4911 and 6721 were for acute and chronic PPH conditions, respectively. The overall crude PPH rate was 7.3 (3.1 for acute and 4.2 for chronic conditions). AN adults had a higher rate than non-AN adults for acute (aRR: 4.7; p < 0.001) and chronic (aRR: 2.6; p < 0.001) PPH conditions. Adults aged ≥ 85 years had the highest PPH rate for acute (43.5) and chronic (31.6) conditions. Acute conditions with the highest PPH rate were bacterial pneumonia (1.8) and urinary tract infections (0.8). Chronic conditions with the highest PPH rate were chronic obstructive pulmonary disease (COPD; 1.6) and congestive heart failure (CHF; 1.3).

CONCLUSION

Efforts to reduce PPHs caused by COPD, CHF, and bacterial pneumonia, especially among AN people and older adults, should yield the greatest benefit in achieving the HA2020 goal.

Hospital Revisits Within 30 Days After Conventional and Robotically Assisted Hysterectomy

OBJECTIVES

To compare the rates of hospital readmissions, emergency department, and outpatient clinic visits after discharge for robotically assisted (RA) versus nonrobotic hysterectomy in women age 30 or more with nonmalignant conditions.

DATA SOURCES

Discharges for 2011 for 8 states (CA, FL, GA, IA, MO, NE, NY, TN) (>86,000 inpatient hysterectomies) were drawn from the statewide databases of the Healthcare Cost and Utilization Project. Data from 4 of these states were used to study revisits after 29,000 outpatient hysterectomies.

METHODS

Matched pairs of patients were constructed with propensity scores derived from each patient's age group, severity of illness, insurance coverage, and type of procedure. Both the full set of revisits and a set limited to diagnoses for revisits judged in other research to be related to the initial surgery (about 70% of all revisits) were analyzed. The analyses were repeated with an instrumental variables regression design.

KEY RESULTS

Using the propensity score matched pairs, revisits, and specifically readmissions, after inpatient hysterectomy were greater for RA versus non-RA patients (relative risk of readmission=124%, P<0.01). Similar results were found for readmissions after outpatient hysterectomy, and readmissions after inpatient hysterectomy for the restricted set of related revisits. In the method with instrumental variables, RA was associated with an increase of 32% in the likelihood of any revisit (P<0.01).

CONCLUSIONS

Using 2 different methods to control for selection, this study found higher rates of revisits among women undergoing RA versus non-RA hysterectomy for benign conditions. While selection bias cannot be ruled out completely in an observational study, the study supports broader use of revisits for analyses of outcomes of hysterectomy.

Impact of Race/Ethnicity and Socioeconomic Status on Risk-Adjusted Readmission Rates

Under the Hospital Readmissions Reduction Program (HRRP) of the Centers for Medicare & Medicaid Services (CMS), hospitals with excess readmissions for select conditions and procedures are penalized. However, readmission rates are not risk adjusted for socioeconomic status (SES) or race/ethnicity. We examined how adding SES and race/ethnicity to the CMS risk-adjustment algorithm would affect hospitals’ excess readmission ratios and potential penalties under the HRRP. For each HRRP measure, we compared excess readmission ratios with and without SES and race/ethnicity included in the CMS standard risk-adjustment algorithm and estimated the resulting effects on overall penalties across a number of hospital characteristics. For the 5 HRRP measures (heart failure, acute myocardial infarction, chronic obstructive pulmonary disease, pneumonia, and total hip or knee arthroplasty), we used data from the Healthcare Cost and Utilization Project’s State Inpatient Databases for 2011-2012 to calculate the excess readmission ratio with and without SES and race/ethnicity included in the model. With these ratios, we estimated the impact on HRRP penalties and found that risk adjusting for SES and race/ethnicity would affect Medicare payments for 83.8% of hospitals. The effect on the size of HRRP penalties ranged from −14.4% to 25.6%, but the impact on overall Medicare base payments was small—ranging from −0.09% to 0.06%. Including SES and race/ethnicity in the calculation had a disproportionately favorable effect on safety-net and rural hospitals. Any financial effects on hospitals and on the Medicare program of adding SES and race/ethnicity to the HRRP risk-adjustment calculation likely would be small.

Lower respiratory tract infection hospitalizations among American Indian/Alaska Native children and the general United States child population

BACKGROUND

The lower respiratory tract infection (LRTI)-associated hospitalization rate in American Indian and Alaska Native (AI/AN) children aged <5 years declined during 1998-2008, yet remained 1.6 times higher than the general US child population in 2006-2008.

PURPOSE

Describe the change in LRTI-associated hospitalization rates for AI/AN children and for the general US child population aged <5 years.

METHODS

A retrospective analysis of hospitalizations with discharge ICD-9-CM codes for LRTI for AI/AN children and for the general US child population <5 years during 2009-2011 was conducted using Indian Health Service direct and contract care inpatient data and the Nationwide Inpatient Sample, respectively. We calculated hospitalization rates and made comparisons to previously published 1998-1999 rates prior to pneumococcal conjugate vaccine introduction.

RESULTS

The average annual LRTI-associated hospitalization rate declined from 1998-1999 to 2009-2011 in AI/AN (35%, p<0.01) and the general US child population (19%, SE: 4.5%, p<0.01). The 2009-2011 AI/AN child average annual LRTI-associated hospitalization rate was 20.7 per 1,000, 1.5 times higher than the US child rate (13.7 95% CI: 12.6-14.8). The Alaska (38.9) and Southwest regions (27.3) had the highest rates. The disparity was greatest for infant (<1 year) pneumonia-associated and 2009-2010 H1N1 influenza-associated hospitalizations.

CONCLUSIONS

Although the LRTI-associated hospitalization rate declined, the 2009-2011 AI/AN child rate remained higher than the US child rate, especially in the Alaska and Southwest regions. The residual disparity is likely multi-factorial and partly related to household crowding, indoor smoke exposure, lack of piped water and poverty. Implementation of interventions proven to reduce LRTI is needed among AI/AN children.

Prevalence of Total Hip and Knee Replacement in the United States

BACKGROUND

Descriptive epidemiology of total joint replacement procedures is limited to annual procedure volumes (incidence). The prevalence of the growing number of individuals living with a total hip or total knee replacement is currently unknown. Our objective was to estimate the prevalence of total hip and total knee replacement in the United States.

METHODS

Prevalence was estimated using the counting method by combining historical incidence data from the National Hospital Discharge Survey and the Healthcare Cost and Utilization Project (HCUP) State Inpatient Databases from 1969 to 2010 with general population census and mortality counts. We accounted for relative differences in mortality rates between those who have had total hip or knee replacement and the general population.

RESULTS

The 2010 prevalence of total hip and total knee replacement in the total U.S. population was 0.83% and 1.52%, respectively. Prevalence was higher among women than among men and increased with age, reaching 5.26% for total hip replacement and 10.38% for total knee replacement at eighty years. These estimates corresponded to 2.5 million individuals (1.4 million women and 1.1 million men) with total hip replacement and 4.7 million individuals (3.0 million women and 1.7 million men) with total knee replacement in 2010. Secular trends indicated a substantial rise in prevalence over time and a shift to younger ages.

CONCLUSIONS

Around 7 million Americans are living with a hip or knee replacement, and consequently, in most cases, are mobile, despite advanced arthritis. These numbers underscore the substantial public health impact of total hip and knee arthroplasties.

Reduced-Dose Schedule of Prophylaxis Based on Local Data Provides Near-Optimal Protection Against Respiratory Syncytial Virus

BACKGROUND

Respiratory syncytial virus (RSV) is a major cause of respiratory infections among young children and can lead to severe disease among some infants. Infants at high risk for severe RSV infection receive monthly injections of a prophylactic monoclonal antibody during the RSV season based on national guidelines. We considered whether a reduced-dose schedule tailored to the local RSV season in the continental United States would provide adequate protection.

METHODS

Hospitalization data for 1942 counties across 38 states from 1997 to 2009 were obtained from the State Inpatient Databases (Agency for Healthcare Research and Quality). We assessed the timing of RSV epidemics at the county and state levels using a 2-stage hierarchical Bayesian change point model. We used a simple summation approach to estimate the fraction of RSV cases that occur during the window of protection provided by initiating RSV prophylaxis during different weeks of the year.

RESULTS

The timing of RSV epidemic onset varied significantly at the local level. Nevertheless, the national recommendations for initiation of prophylaxis provided near-optimal coverage of the RSV season in most of the continental United States. Reducing from 5 to 4 monthly doses (with a later initiation) provides near-optimal coverage (<5% decrease in coverage) in most settings. Earlier optimal dates for initiating 4 doses of prophylaxis were associated with being farther south and east, higher population density, and having a higher percentage of the population that was black or Hispanic.

CONCLUSIONS

A 4-dose schedule of prophylactic injections timed with local RSV epidemics could provide protection comparable to 5 doses and could be considered as a way to improve the cost-effectiveness of prophylaxis.

Spatial epidemiology of blastomycosis hospitalizations: detecting clusters and identifying environmental risk factors

Blastomycosis is a disease caused by endemic fungi that ranges from severe pulmonary or disseminated to mild or asymptomatic. Environmental factors associated with it are not well described throughout the endemic area. We used the intramural State Inpatient Database from the Agency for Healthcare Research and Quality and ArcMap GIS to identify geographic high-risk clusters of blastomycosis hospitalizations in 13 states in the US endemic regions (AR, IA, IL, IN, KY, LA, MI, MN, MO, MS, OH, TN, and WI). We then used logistic regression to identify risk factors associated with these high-risk clusters. We describe six clusters of counties in which there was an elevated incidence of blastomycosis hospitalizations. We identified maximum mean annual temperature, percentage of persons aged ≥65 years, and mercury and copper soil content as being associated with high-risk clusters. Specifically, the odds of a county being part of a high-risk cluster was associated with increasing percentage of population over age 65, decreasing maximum temperature, increasing mercury, and decreasing copper soil content. Healthcare providers should be aware of these high-risk areas so that blastomycosis can be included, as appropriate, in a differential diagnosis for patients currently or previously residing in these areas.

Epidemiology of asthma hospitalizations among American Indian and Alaska Native people and the general United States population

BACKGROUND

Asthma, a common chronic disease among adults and children in the United States, results in nearly one-half million hospitalizations annually. There has been no evaluation of asthma hospitalizations for American Indian and Alaska Native (AI/AN) people since a previous study using data for 1988-2002. In this study, we describe the epidemiology and trends for asthma hospitalizations among AI/AN people and the general US population for 2003-2011.

METHODS

Hospital discharge records with a first-listed diagnosis of asthma for 2003-2011 were examined for AI/AN people, using Indian Health Service (IHS) data, and for the general US population, using the Nationwide Inpatient Sample. Average annual crude and age-adjusted hospitalization rates were calculated.

RESULTS

The average annual asthma hospitalization rates for AI/AN people and the general US population decreased from 2003-2005 to 2009-2011 (32% and 11% [SE, 3%], respectively). The average annual age-adjusted rate for 2009-2011 was lower for AI/AN people (7.6 per 10,000 population) compared with the general US population (13.2 per 10,000; 95% CI, 12.8-13.6). Age-specific AI/AN rates were highest among infants and children 1 to 4 years of age. IHS regional rates declined in all regions except Alaska.

CONCLUSIONS

Asthma hospitalization rates are decreasing for AI/AN people and the general US population despite increasing prevalence rates. AI/AN people experienced a substantially lower age-adjusted asthma hospitalization rate compared with the general US population. Although the rates for AI/AN infants and children 1 to 4 years of age have declined substantially, they remain higher compared with other age groups. Improved disease management and awareness should help to further decrease asthma hospitalizations, particularly among young children.

Environmental drivers of the spatiotemporal dynamics of respiratory syncytial virus in the United States

Epidemics of respiratory syncytial virus (RSV) are known to occur in wintertime in temperate countries including the United States, but there is a limited understanding of the importance of climatic drivers in determining the seasonality of RSV. In the United States, RSV activity is highly spatially structured, with seasonal peaks beginning in Florida in November through December and ending in the upper Midwest in February-March, and prolonged disease activity in the southeastern US. Using data on both age-specific hospitalizations and laboratory reports of RSV in the US, and employing a combination of statistical and mechanistic epidemic modeling, we examined the association between environmental variables and state-specific measures of RSV seasonality. Temperature, vapor pressure, precipitation, and potential evapotranspiration (PET) were significantly associated with the timing of RSV activity across states in univariate exploratory analyses. The amplitude and timing of seasonality in the transmission rate was significantly correlated with seasonal fluctuations in PET, and negatively correlated with mean vapor pressure, minimum temperature, and precipitation. States with low mean vapor pressure and the largest seasonal variation in PET tended to experience biennial patterns of RSV activity, with alternating years of “early-big” and “late-small” epidemics. Our model for the transmission dynamics of RSV was able to replicate these biennial transitions at higher amplitudes of seasonality in the transmission rate. This successfully connects environmental drivers to the epidemic dynamics of RSV; however, it does not fully explain why RSV activity begins in Florida, one of the warmest states, when RSV is a winter-seasonal pathogen. Understanding and predicting the seasonality of RSV is essential in determining the optimal timing of immunoprophylaxis.

Respiratory syncytial virus (RSV) causes annual outbreaks of respiratory disease every winter in temperate climates, which can be severe particularly among infants. In the United States, RSV activity begins each autumn in Florida and appears to spread from the southeast to the northwest. Using data on hospitalizations and laboratory tests for RSV, we show that the timing of epidemics is associated with a variety of climatic factors, including temperature, vapor pressure, precipitation, and potential evapotranspiration (PET). Furthermore, using a dynamic model, we show that seasonal variation in the transmission rate of RSV can be correlated with the amplitude and timing of variation in PET, which is a measure of demand for water from the atmosphere. States with colder, drier weather and a large seasonal swing in PET tended to experience an alternating pattern of “early-big” RSV epidemics one year followed by a “late-small” epidemic the next year, which our model was able to reproduce based on the interaction between susceptible and infectious individuals. However, we cannot fully explain why epidemics begin in Florida. Being able to understand and predict the timing of RSV activity is important for optimizing the delivery of immunoprophylaxis to high-risk individuals.

Incidence and trends of blastomycosis-associated hospitalizations in the United States

We used the State Inpatient Databases from the United States Agency for Healthcare Research and Quality to provide state-specific age-adjusted blastomycosis-associated hospitalization incidence throughout the entire United States. Among the 46 states studied, states within the Mississippi and Ohio River valleys had the highest age-adjusted hospitalization incidence. Specifically, Wisconsin had the highest age-adjusted hospitalization incidence (2.9 hospitalizations per 100,000 person-years). Trends were studied in the five highest hospitalization incidence states. From 2000 to 2011, blastomycosis-associated hospitalizations increased significantly in Illinois and Kentucky with an average annual increase of 4.4% and 8.4%, respectively. Trends varied significantly by state. Overall, 64% of blastomycosis-associated hospitalizations were among men and the median age at hospitalization was 53 years. This analysis provides a complete epidemiologic description of blastomycosis-associated hospitalizations throughout the endemic area in the United States.

Impact of varicella vaccination on varicella-related hospitalizations among American Indian/Alaska Native people

BACKGROUND

Routine childhood varicella vaccination, implemented in 1995, has resulted in significant declines in varicella-related hospitalizations in the United States. Varicella hospitalization rates among the American Indian (AI) and Alaska Native (AN) population have not been previously documented.

METHODS

We selected varicella-related hospitalizations, based on a published definition, from the Indian Health Service inpatient database for AI/ANs in the Alaska, Southwest and Northern Plains regions (1995-2010) and from the Nationwide Inpatient Sample for the general US population (2007-2010). We analyzed average annual hospitalization rates prevaccine (1995-1998) and postvaccine (2007-2010) for the AI/AN population, and postvaccine for the general US population.

RESULTS

From 1995-1998 to 2007-2010, the average annual varicella-related hospitalization rate for AI/ANs in the 3 regions decreased 95% (0.66-0.03/10,000 persons); the postvaccine rate appears lower than the general US rate (0.06, 95% confidence interval: 0.05-0.06). The rate declined in all AI/AN pediatric age groups. Infants experienced the highest prevaccine (14.07) and postvaccine (0.83) hospitalization rates. Adults experienced low rates in both periods. Varicella vaccination rates in 19- to 35-month-old AI/AN children during fiscal years 2008-2010 were 88.1-91.0%.

CONCLUSIONS

Widespread use of varicella vaccine in AI/AN children was accompanied by substantial declines in varicella-related hospitalizations consistent with high varicella vaccine effectiveness in preventing severe varicella outcomes.

Influenza hospitalizations among american indian/alaska native people and in the United States general population

BACKGROUND

Historically, American Indian/Alaska Native (AI/AN) people have experienced a disproportionate burden of infectious disease morbidity compared with the general US population. We evaluated whether a disparity in influenza hospitalizations exists between AI/AN people and the general US population.

METHODS

We used Indian Health Service hospital discharge data (2001-2011) for AI/AN people and 13 State Inpatient Databases (2001-2008) to provide a comparison to the US population. Hospitalization rates were calculated by respiratory year (July-June). Influenza-specific hospitalizations were defined as discharges with any influenza diagnoses. Influenza-associated hospitalizations were calculated using negative binomial regression models that incorporated hospitalization and influenza laboratory surveillance data.

RESULTS

The mean influenza-specific hospitalization rate/100 000 persons/year during the 2001-2002 to 2007-2008 respiratory years was 18.6 for AI/AN people and 15.6 for the comparison US population. The age-adjusted influenza-associated hospitalization rate for AI/AN people (98.2; 95% confidence interval [CI], 51.6-317.8) was similar to the comparison US population (58.2; CI, 34.7-172.2). By age, influenza-associated hospitalization rates were significantly higher among AI/AN infants (<1 year) (1070.7; CI, 640.7-2969.5) than the comparison US infant population (210.2; CI, 153.5-478.5).

CONCLUSIONS

American Indian/Alaska Native people had higher influenza-specific hospitalization rates than the comparison US population; a significant influenza-associated hospitalization rate disparity was detected only among AI/AN infants because of the wide CIs inherent to the model. Taken together, the influenza-specific and influenza-associated hospitalization rates suggest that AI/AN people might suffer disproportionately from influenza illness compared with the general US population.

Surgical site infections following ambulatory surgery procedures

IMPORTANCE

Surgical site infections can result in substantial morbidity following inpatient surgery. Little is known about serious infections following ambulatory surgery.

OBJECTIVE

To determine the incidence of clinically significant surgical site infections (CS-SSIs) following low- to moderate-risk ambulatory surgery in patients with low risk for surgical complications.

DESIGN, SETTING, AND PARTICIPANTS

Retrospective analysis of ambulatory surgical procedures complicated by CS-SSIs that require a postsurgical acute care visit (defined as subsequent hospitalization or ambulatory surgical visit for infection) using the 2010 Healthcare Cost and Utilization Project State Ambulatory Surgery and State Inpatient Databases for 8 geographically dispersed states (California, Florida, Georgia, Hawaii, Missouri, Nebraska, New York, and Tennessee) representing one-third of the US population. Index cases included 284 098 ambulatory surgical procedures (general surgery, orthopedic, neurosurgical, gynecologic, and urologic) in adult patients with low surgical risk (defined as not seen in past 30 days in acute care, length of stay less than 2 days, no other surgery on the same day, and discharged home and no infection coded on the same day).

MAIN OUTCOMES AND MEASURES

Rates of 14- and 30-day postsurgical acute care visits for CS-SSIs following ambulatory surgery.

RESULTS

Postsurgical acute care visits for CS-SSIs occurred in 3.09 (95% CI, 2.89-3.30) per 1000 ambulatory surgical procedures at 14 days and 4.84 (95% CI, 4.59-5.10) per 1000 at 30 days. Two-thirds (63.7%) of all visits for CS-SSI occurred within 14 days of the surgery; of those visits, 93.2% (95% CI, 91.3%-94.7%) involved treatment in the inpatient setting. All-cause inpatient or outpatient postsurgical visits, including those for CS-SSIs, following ambulatory surgery occurred in 19.99 (95% CI, 19.48-20.51) per 1000 ambulatory surgical procedures at 14 days and 33.62 (95% CI, 32.96-34.29) per 1000 at 30 days.

CONCLUSIONS AND RELEVANCE

Among patients in 8 states undergoing ambulatory surgery, rates of postsurgical visits for CS-SSIs were low relative to all causes; however, they may represent a substantial number of adverse outcomes in aggregate. Thus, these serious infections merit quality improvement efforts to minimize their occurrence.

Burden of encephalitis-associated hospitalizations in the United States, 1998-2010

OBJECTIVE

To estimate the burden of encephalitis-associated hospitalizations in the United States for 1998-2010.

METHODS

Using the Nationwide Inpatient Sample, a nationally representative database of hospitalizations, estimated numbers and rates of encephalitis-associated hospitalizations for 1998-2010 were calculated. Etiology and outcome of encephalitis-associated hospitalizations were examined, as well as accompanying diagnoses listed along with encephalitis on the discharge records. Total hospital charges (in 2010 US dollars) were assessed.

RESULTS

An estimated 263,352 (standard error: 3,017) encephalitis-associated hospitalizations occurred in the United States during 1998-2010, which corresponds to an average of 20,258 (standard error: 232) encephalitis-associated hospitalizations per year. A fatal outcome occurred in 5.8% (95% confidence interval [CI]: 5.6%-6.0%) of all encephalitis-associated hospitalizations and in 10.1% (95% CI: 9.2%-11.2%) and 17.1% (95% CI: 14.6%-20.0%) of encephalitis-associated hospitalizations in which a code for HIV or a tissue or organ transplant was listed, respectively. The proportion of encephalitis-associated hospitalizations in which an etiology for encephalitis was specified was 50.3% (95% CI: 49.6%-51.0%) and that for which the etiology was unspecified was 49.7% (95% CI: 49.0%-50.4%). Total charges for encephalitis-associated hospitalizations in 2010 were an estimated $2.0 billion.

CONCLUSIONS

Encephalitis remains a major public health concern in the United States. Among the large number of encephalitis-associated hospitalizations for which an etiology is not reported may be novel infectious and noninfectious forms of encephalitis. Associated conditions such as HIV or transplantation increase the risk of a fatal outcome from an encephalitis-associated hospitalization and should be monitored.

Seasonal drivers of pneumococcal disease incidence: impact of bacterial carriage and viral activity

BACKGROUND

Winter-seasonal epidemics of pneumococcal disease provide an opportunity to understand the drivers of incidence. We sought to determine whether seasonality of invasive pneumococcal disease is caused by increased nasopharyngeal transmission of the bacteria or increased susceptibility to invasive infections driven by cocirculating winter respiratory viruses.

METHODS

We analyzed pneumococcal carriage and invasive disease data collected from children <7 years old in the Navajo/White Mountain Apache populations between 1996 and 2012. Regression models were used to quantify seasonal variations in carriage prevalence, carriage density, and disease incidence. We also fit a multivariate model to determine the contribution of carriage prevalence and RSV activity to pneumococcal disease incidence while controlling for shared seasonal factors.

RESULTS

The seasonal patterns of invasive pneumococcal disease epidemics varied significantly by clinical presentation: bacteremic pneumococcal pneumonia incidence peaked in late winter, whereas invasive nonpneumonia pneumococcal incidence peaked in autumn. Pneumococcal carriage prevalence and density also varied seasonally, with peak prevalence occurring in late autumn. In a multivariate model, RSV activity was associated with significant increases in bacteremic pneumonia cases (attributable percentage, 15.5%; 95% confidence interval [CI], 1.8%-26.1%) but was not associated with invasive nonpneumonia infections (8.0%; 95% CI, -4.8% to 19.3%). In contrast, seasonal variations in carriage prevalence were associated with significant increases in invasive nonpneumonia infections (31.4%; 95% CI, 8.8%-51.4%) but not with bacteremic pneumonia.

CONCLUSIONS

The seasonality of invasive pneumococcal pneumonia could be due to increased susceptibility to invasive infection triggered by viral pathogens, whereas seasonality of other invasive pneumococcal infections might be primarily driven by increased nasopharyngeal transmission of the bacteria.

Increasing trend in the rate of infectious disease hospitalisations among Alaska Native people

OBJECTIVES

To examine the epidemiology of infectious disease (ID) hospitalisations among Alaska Native (AN) people.

METHODS

Hospitalisations with a first-listed ID diagnosis for American Indians and ANs residing in Alaska during 2001-2009 were selected from the Indian Health Service direct and contract health service inpatient data. ID hospitalisations to describe the general US population were selected from the Nationwide Inpatient Sample. Annual and average annual (2007-2009) hospitalization rates were calculated.

RESULTS

During 2007-2009, IDs accounted for 20% of hospitalisations among AN people. The 2007-2009 average annual age-adjusted ID hospitalisation rate (2126/100,000 persons) was higher than that for the general US population (1679/100,000; 95% CI 1639-1720). The ID hospitalisation rate for AN people increased from 2001 to 2009 (17%, p < 0.001). Although the rate during 2001-2009 declined for AN infants (< 1 year of age; p = 0.03), they had the highest 2007-2009 average annual rate (15106/100,000), which was 3 times the rate for general US infants (5215/100,000; 95% CI 4783-5647). The annual rates for the age groups 1-4, 5-19, 40-49, 50-59 and 70-79 years increased (p < 0.05). The highest 2007-2009 age-adjusted average annual ID hospitalisation rates were in the Yukon-Kuskokwim (YK) (3492/100,000) and Kotzebue (3433/100,000) regions; infant rates were 30422/100,000 and 26698/100,000 in these regions, respectively. During 2007-2009, lower respiratory tract infections accounted for 39% of all ID hospitalisations and approximately 50% of ID hospitalisations in YK, Kotzebue and Norton Sound, and 74% of infant ID hospitalisations.

CONCLUSIONS

The ID hospitalisation rate increased for AN people overall. The rate for AN people remained higher than that for the general US population, particularly in infants and in the YK and Kotzebue regions. Prevention measures to reduce ID morbidity among AN people should be increased in high-risk regions and for diseases with high hospitalisation rates.