A method for partitioning the attributable fraction of multiple time-dependent coexisting risk factors for an adverse health outcome

The Contribution of Chronic Conditions to Hospitalization, Skilled Nursing Facility Admission, and Death: Variation by Race

Multimorbidity (≥2 chronic conditions) is a common and important marker of aging. To better understand racial differences in multimorbidity burden and associations with important health-related outcomes, we assessed differences in the contribution of chronic conditions to hospitalization, skilled nursing facility admission, and mortality among non-Hispanic Black and non-Hispanic White older adults in the United States. We used data from a nationally representative study, the National Health and Aging Trends Study, linked to Medicare claims from 2011-2015 (n = 4,871 respondents). This analysis improved upon prior research by identifying the absolute contributions of chronic conditions using a longitudinal extension of the average attributable fraction for Black and White Medicare beneficiaries. We found that cardiovascular conditions were the greatest contributors to outcomes among White respondents, while the greatest contributor to outcomes for Black respondents was renal morbidity. This study provides important insights into racial differences in the contributions of chronic conditions to costly health-care utilization and mortality, and it prompts policy-makers to champion delivery reforms that will expand access to preventive and ongoing care for diverse Medicare beneficiaries.

The Population Impact of Late Presentation With Advanced HIV Disease and Delayed Antiretroviral Therapy in Adults Receiving HIV Care in Latin America

Late presentation to care and antiretroviral therapy (ART) initiation with advanced human immunodeficiency virus (HIV) disease are common in Latin America. We estimated the impact of these conditions on mortality in the region. We included adults enrolled during 2001-2014 at HIV care clinics. We estimated the adjusted attributable risk (AR) and population attributable fraction (PAF) for all-cause mortality of presentation to care with advanced HIV disease (advanced LP), ART initiation with advanced HIV disease, and not initiating ART. Advanced HIV disease was defined as CD4 of <200 cells/μL or acquired immune deficiency syndrome. AR and PAF were derived using marginal structural models. Of 9,229 patients, 56% presented with advanced HIV disease. ARs of death for advanced LP were 86%, 71%, and 58%, and PAFs were 78%, 58%, and 43% at 1, 5, and 10 years after enrollment. Among people without advanced LP, ARs of death for delaying ART were 39%, 32%, and 37% at 1, 5, and 10 years post-enrollment and PAFs were 20%, 14%, and 15%. Among people with advanced LP, ART decreased the hazard of death by 63% in the first year after enrollment, but 93% of these started ART; thus universal ART among them would reduce mortality by only 10%. Earlier presentation to care and earlier ART initiation would prevent most HIV deaths in Latin America.

Contributions of COPD, asthma, and ten comorbid conditions to health care utilization and patient-centered outcomes among US adults with obstructive airway disease

Background

Among persons with obstructive airway disease, the relative contributions of chronic obstructive pulmonary disease (COPD), asthma, and common comorbid conditions to health care utilization and patient-centered outcomes (PCOs) have not been previously reported.

Methods

We followed a total of 3,486 persons aged ≥40 years with COPD, asthma, or both at baseline, from the Medical Expenditure Panel Survey (MEPS) cohorts enrolled annually from 2008 through 2012 for 1 year. MEPS is a prospective observational study of US households recording self-reported COPD, asthma, and ten medical conditions: angina, arthritis, cancer, coronary heart disease, cognitive impairment, diabetes, hypertension, lung cancer, myocardial infarction, and stroke/transient ischemic attack. We studied the separate contributions of these conditions to health care utilization (all-cause and respiratory disease hospitalization, any emergency department [ED] visit, and six or more outpatient visits) and PCOs (seven or more days spent in bed due to illness, incident loss of mobility, and incident decline in self-perceived health).

Results

COPD made the largest contributions to all-cause and respiratory disease hospitalization and ED visits, while arthritis made the largest contribution to outpatient health care. Arthritis and COPD, respectively, made the greatest contributions to the PCOs.

Conclusion

COPD made the largest and second largest contributions to health care utilization and PCOs among US adults with obstructive airway disease. The twelve medical conditions collectively accounted for between 52% and 61% of the health care utilization outcomes and between 53% and 68% of the PCOs. Cognitive impairment, diabetes, hypertension, and stroke also made significant contributions.

Pilot study to test the feasibility of a trial design and complex intervention on PRIoritising MUltimedication in Multimorbidity in general practices (PRIMUMpilot)

OBJECTIVE

To improve medication appropriateness and adherence in elderly patients with multimorbidity, we developed a complex intervention involving general practitioners (GPs) and their healthcare assistants (HCA). In accordance with the Medical Research Council guidance on developing and evaluating complex interventions, we prepared for the main study by testing the feasibility of the intervention and study design in a cluster randomised pilot study.

SETTING

20 general practices in Hesse, Germany.

PARTICIPANTS

100 cognitively intact patients ≥65 years with ≥3 chronic conditions, ≥5 chronic prescriptions and capable of participating in telephone interviews; 94 patients completed the study.

INTERVENTION

The HCA conducted a checklist-based interview with patients on medication-related problems and reconciled their medications. Assisted by a computerised decision-support system (CDSS), the GPs discussed medication intake with patients and adjusted their medication regimens. The control group continued with usual care.

OUTCOME MEASURES

Feasibility of the intervention and required time were assessed for GPs, HCAs and patients using mixed methods (questionnaires, interviews and case vignettes after completion of the study). The feasibility of the study was assessed concerning success of achieving recruitment targets, balancing cluster sizes and minimising drop-out rates. Exploratory outcomes included the medication appropriateness index (MAI), quality of life, functional status and adherence-related measures. MAI was evaluated blinded to group assignment, and intra-rater/inter-rater reliability was assessed for a subsample of prescriptions.

RESULTS

10 practices were randomised and analysed per group. GPs/HCAs were satisfied with the interventions despite the time required (35/45 min/patient). In case vignettes, GPs/HCAs needed help using the CDSS. The study made no patients feel uneasy. Intra-rater/inter-rater reliability for MAI was excellent. Inclusion criteria were challenging and potentially inadequate, and should therefore be adjusted. Outcome measures on pain, functionality and self-reported adherence were unfeasible due to frequent missing values, an incorrect manual or potentially invalid results.

CONCLUSIONS

Intervention and trial design were feasible. The pilot study revealed important limitations that influenced the design and conduct of the main study, thus highlighting the value of piloting complex interventions.

TRIAL REGISTRATION NUMBER

ISRCTN99691973; Results.

Methodology to Estimate the Longitudinal Average Attributable Fraction of Guideline-recommended Medications for Death in Older Adults With Multiple Chronic Conditions

BACKGROUND

Persons with multiple chronic conditions receive multiple guideline-recommended medications to improve outcomes such as mortality. Our objective was to estimate the longitudinal average attributable fraction for 3-year survival of medications for cardiovascular conditions in persons with multiple chronic conditions and to determine whether heterogeneity occurred by age.

METHODS

Medicare Current Beneficiary Survey participants (N = 8,578) with two or more chronic conditions, enrolled from 2005 to 2009 with follow-up through 2011, were analyzed. We calculated the longitudinal extension of the average attributable fraction for oral medications (beta blockers, renin-angiotensin system blockers, and thiazide diuretics) indicated for cardiovascular conditions (atrial fibrillation, coronary artery disease, heart failure, and hypertension), on survival adjusted for 18 participant characteristics. Models stratified by age (≤80 and >80 years) were analyzed to determine heterogeneity of both cardiovascular conditions and medications.

RESULTS

Heart failure had the greatest average attributable fraction (39%) for mortality. The fractional contributions of beta blockers, renin-angiotensin system blockers, and thiazides to improve survival were 10.4%, 9.3%, and 7.2% respectively. In age-stratified models, of these medications thiazides had a significant contribution to survival only for those aged 80 years or younger. The effects of the remaining medications were similar in both age strata.

CONCLUSIONS

Most cardiovascular medications were attributed independently to survival. The two cardiovascular conditions contributing independently to death were heart failure and atrial fibrillation. The medication effects were similar by age except for thiazides that had a significant contribution to survival in persons younger than 80 years.

Contribution of chronic diseases to the mild and severe disability burden in Belgium

BACKGROUND

Population aging accompanied by an increased longevity with disability has raised international concern, especially due to its costs to the health care systems. Chronic diseases are the main causes of physical disability and their simultaneous occurrence in the population can impact the disablement process, resulting in different severity levels. In this study, the contribution of chronic diseases to both mild and severe disability burden in Belgium was investigated.

METHODS

Data on 21 chronic diseases and disability from 35,799 individuals aged 15 years or older who participated in the 1997, 2001, 2004, or 2008 Belgian Health Interview Surveys were analysed. Mild and severe disability were defined based on questions related to six activities of daily living and/or mobility limitations. To attribute disability by severity level to selected chronic diseases, multiple additive hazard models were fitted to each disability outcome, separately for men and women.

RESULTS

A stable prevalence of mild (5 %) and severe (2-3 %) disability was observed for the Belgian population aged 15 years or older between 1997 and 2008. Arthritis was the most important contributor in women with mild and severe disability. In men, low back pain and chronic respiratory diseases contributed most to the mild and severe disability burden, respectively. The contribution also differed by age: for mild disability, depression and chronic respiratory diseases were important contributors among young individuals, while heart attack had a large contribution for older individuals. For severe disability, neurological diseases and stroke presented a large contribution in young and elderly individuals, respectively.

CONCLUSIONS

Our results indicate that the assessment of the contribution of chronic diseases on disability is more informative if different levels of disability are taken into consideration. The identification of diseases which are related to different levels of disability - mild and severe - can assist policymakers in the definition and prioritisation of strategies to tackle disability, involving prevention, rehabilitation programs, support services, and training for disabled individuals.

Longitudinal average attributable fraction as a method for studying time-varying conditions and treatments on recurrent self-rated health: the case of medications in older adults with multiple chronic conditions

PURPOSE

The objective is to modify the longitudinal extension of the average attributable fraction (LE-AAF) for recurrent outcomes with time-varying exposures and control for covariates.

METHODS

We included Medicare Current Beneficiary Survey participants with two or more chronic conditions enrolled from 2005 to 2009 with follow-up through 2011. Nine time-varying medications indicated for nine time-varying common chronic conditions and 14 of 18 forward-selected participant characteristics were used as control variables in the generalized estimating equations step of the LE-AAF to estimate associations with the recurrent universal health outcome self-rated health (SRH). Modifications of the LE-AAF were made to accommodate these indicated medication-condition interactions and covariates. Variability was empirically estimated by bias-corrected and accelerated bootstrapping.

RESULTS

In the adjusted LE-AAF, thiazide, warfarin, and clopidogrel had significant contributions of 1.2%, 0.4%, 0.2%, respectively, to low (poor or fair) SRH; whereas there were no significant contributions of the other medications to SRH. Hyperlipidemia significantly contributed 4.6% to high SRH. All the other conditions except atrial fibrillation contributed significantly to low SRH.

CONCLUSIONS

Our modifications to the LE-AAF method apply to a recurrent binary outcome with time-varying factors accounting for covariates.

Preventable major cardiovascular events associated with uncontrolled glucose, blood pressure, and lipids and active smoking in adults with diabetes with and without cardiovascular disease: a contemporary analysis

OBJECTIVE

The objective of this study was to assess the incidence of major cardiovascular (CV) hospitalization events and all-cause deaths among adults with diabetes with or without CV disease (CVD) associated with inadequately controlled glycated hemoglobin (A1C), high LDL cholesterol (LDL-C), high blood pressure (BP), and current smoking.

RESEARCH DESIGN AND METHODS

Study subjects included 859,617 adults with diabetes enrolled for more than 6 months during 2005-2011 in a network of 11 U.S. integrated health care organizations. Inadequate risk factor control was classified as LDL-C ≥100 mg/dL, A1C ≥7% (53 mmol/mol), BP ≥140/90 mm Hg, or smoking. Major CV events were based on primary hospital discharge diagnoses for myocardial infarction (MI) and acute coronary syndrome (ACS), stroke, or heart failure (HF). Five-year incidence rates, rate ratios, and average attributable fractions were estimated using multivariable Poisson regression models.

RESULTS

Mean (SD) age at baseline was 59 (14) years; 48% of subjects were female, 45% were white, and 31% had CVD. Mean follow-up was 59 months. Event rates per 100 person-years for adults with diabetes and CVD versus those without CVD were 6.0 vs. 1.7 for MI/ACS, 5.3 vs. 1.5 for stroke, 8.4 vs. 1.2 for HF, 18.1 vs. 40 for all CV events, and 23.5 vs. 5.0 for all-cause mortality. The percentages of CV events and deaths associated with inadequate risk factor control were 11% and 3%, respectively, for those with CVD and 34% and 7%, respectively, for those without CVD.

CONCLUSIONS

Additional attention to traditional CV risk factors could yield further substantive reductions in CV events and mortality in adults with diabetes.

Contribution of chronic diseases to the disability burden in a population 15 years and older, Belgium, 1997-2008

Background

Age-associated disability reduces quality of life in older populations and leads to wide-range implications for social and health policy. The identification of diseases that contribute to the disability burden is crucial to the development of prevention and intervention strategies to reduce disability. In this study, we assessed the contribution of chronic diseases to the prevalence of disability in Belgium.

Methods

Data from 35,837 individuals aged 15 years or older who participated in the 1997, 2001, 2004, or 2008 Belgian Health Interview Surveys were used. Disability was defined as difficulties in doing at least one of six activities of daily living (transfer in and out of bed, transfer in and out of chair, dressing, washing hands and face, feeding, and going to the toilet) and/or mobility limitations (ability to walk without stopping less than 200 m). Multiple additive regression models were fitted separately for men and women to estimate the age-specific background disability rate (experienced by everyone, independent of the presence of specific diseases) and disease-specific disability rates (disability rate in subjects who reported selected chronic diseases).

Results

Musculoskeletal, cardiovascular, and respiratory diseases were the main contributors to the disability burden in Belgium. Musculoskeletal diseases were the most prevalent diseases in men and women in all age groups. Neurological diseases and stroke were the most disabling diseases, i.e. caused the highest level of disability among the diseased individuals, in all age groups for men and women, respectively. Back pain was the main cause of disability in men aged 15 to 64 years, while heart attack was the major contributor to the disability prevalence in men aged 65 or older. Likewise, arthritis was the main cause of disability among women across all age groups. Depression was also an important contributor in young subjects (15–54 years). Cancer was not an important contributor to the disability prevalence in Belgium.

Conclusions

To reduce the burden of disability in Belgium, interventions should target musculoskeletal, cardiovascular and respiratory diseases especially among elderly. Furthermore, attention should also be given to depression in young individuals.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-1574-z) contains supplementary material, which is available to authorized users.

Improving the estimation of the burden of risk factors: an illustrative comparison of methods to measure smoking-attributable mortality

Background

Prevention efforts are informed by the numbers of deaths or cases of disease caused by specific risk factors, but these are challenging to estimate in a population. Fortunately, an increasing number of jurisdictions have increasingly rich individual-level, population-based data linking exposures and outcomes. These linkages enable multivariable approaches to risk assessment. We demonstrate how this approach can estimate the population burden of risk factors and illustrate its advantages over often-used population-attributable fraction methods.

Methods

We obtained risk factor information for 78,597 individuals from a series of population-based health surveys. Each respondent was linked to death registry (568,997 person-years of follow-up, 6,399 deaths).Two methods were used to obtain population-attributable fractions. First, the mortality rate difference between the entire population and the population of non-smokers was divided by the total mortality rate. Second, often-used attributable fraction formulas were used to combine summary measures of smoking prevalence with relative risks of death for select diseases. The respective fractions were then multiplied to summary measures of mortality to obtain smoking-attributable mortality. Alternatively, for our multivariable approach, we created algorithms for risk of death, predicted by health behaviors and various covariates (age, sex, socioeconomic position, etc.). The burden of smoking was determined by comparing the predicted mortality of the current population with that of a counterfactual population where smoking is eliminated.

Results

Our multivariable algorithms accurately predicted an individual’s risk of death based on their health behaviors and other variables in the models. These algorithms estimated that 23.7% of all deaths can be attributed to smoking in Ontario. This is higher than the 20.0% estimated using population-attributable risk methods that considered only select diseases and lower than the 35.4% estimated from population-attributable risk methods that examine the excess burden of all deaths due to smoking.

Conclusions

The multivariable algorithms presented have several advantages, including: controlling for confounders, accounting for complexities in the relationship between multiple exposures and covariates, using consistent definitions of exposure, and using specific measures of risk derived internally from the study population. We propose the wider use of multivariable risk assessment approach as an alternative to population-attributable fraction methods.

Modifiable risk factors for pneumonia requiring hospitalization of community-dwelling older adults: the Health, Aging, and Body Composition Study

OBJECTIVES

To identify novel modifiable risk factors, focusing on oral hygiene, for pneumonia requiring hospitalization of community-dwelling older adults.

DESIGN

Prospective observational cohort study.

SETTING

Memphis, Tennessee, and Pittsburgh, Pennsylvania.

PARTICIPANTS

Of 3,075 well-functioning community-dwelling adults aged 70 to 79 enrolled in the Health, Aging, and Body Composition Study from 1997 to 1998, 1,441 had complete data in the data set of all variables used, a dental examination within 6 months of baseline, and were eligible for this study.

MEASUREMENTS

The primary outcome was pneumonia requiring hospitalization through 2008.

RESULTS

Of 1,441 participants, 193 were hospitalized for pneumonia. In a multivariable model, male sex (hazard ratio (HR) = 2.07, 95% confidence interval (CI) = 1.51-2.83), white race (HR = 1.44, 95% CI = 1.03-2.01), history of pneumonia (HR = 3.09, 95% CI = 1.86-5.14), pack-years of smoking (HR = 1.006, 95% CI = 1.001-1.011), and percentage of predicted forced expiratory volume in 1 minute (moderate vs mild lung disease or normal lung function, HR = 1.78, 95% CI = 1.28-2.48; severe lung disease vs mild lung disease or normal lung function, HR = 2.90, 95% CI = 1.51-5.57) were nonmodifiable risk factors for pneumonia. Incident mobility limitation (HR = 1.77, 95% CI = 1.32-2.38) and higher mean oral plaque score (HR = 1.29, 95% CI = 1.02-1.64) were modifiable risk factors for pneumonia. Average attributable fractions revealed that 11.5% of cases of pneumonia were attributed to incident mobility limitation and 10.3% to a mean oral plaque score of 1 or greater.

CONCLUSION

Incident mobility limitation and higher mean oral plaque score were two modifiable risk factors that 22% of pneumonia requiring hospitalization could be attributed to. These data suggest innovative opportunities for pneumonia prevention among community-dwelling older adults.