Bias correction models for electronic health records data in the presence of non-random sampling

Electronic health records (EHRs) contain rich clinical information for millions of patients and are increasingly used for public health research. However, non-random inclusion of subjects in EHRs can result in selection bias, with factors such as demographics, socioeconomic status, healthcare referral patterns, and underlying health status playing a role. While this issue has been well documented, little work has been done to develop or apply bias-correction methods, often due to the fact that most of these factors are unavailable in EHRs. To address this gap, we propose a series of Heckman type bias correction methods by incorporating social determinants of health selection covariates to model the EHR non-random sampling probability. Through simulations under various settings, we demonstrate the effectiveness of our proposed method in correcting biases in both the association coefficient and the outcome mean. Our method augments the utility of EHRs for public health inferences, as we show by estimating the prevalence of cardiovascular disease and its correlation with risk factors in the New York City network of EHRs.

Using electronic health records to enhance surveillance of diabetes in children, adolescents and young adults: a study protocol for the DiCAYA Network

INTRODUCTION

Traditional survey-based surveillance is costly, limited in its ability to distinguish diabetes types and time-consuming, resulting in reporting delays. The Diabetes in Children, Adolescents and Young Adults (DiCAYA) Network seeks to advance diabetes surveillance efforts in youth and young adults through the use of large-volume electronic health record (EHR) data. The network has two primary aims, namely: (1) to refine and validate EHR-based computable phenotype algorithms for accurate identification of type 1 and type 2 diabetes among youth and young adults and (2) to estimate the incidence and prevalence of type 1 and type 2 diabetes among youth and young adults and trends therein. The network aims to augment diabetes surveillance capacity in the USA and assess performance of EHR-based surveillance. This paper describes the DiCAYA Network and how these aims will be achieved.

METHODS AND ANALYSIS

The DiCAYA Network is spread across eight geographically diverse US-based centres and a coordinating centre. Three centres conduct diabetes surveillance in youth aged 0-17 years only (component A), three centres conduct surveillance in young adults aged 18-44 years only (component B) and two centres conduct surveillance in components A and B. The network will assess the validity of computable phenotype definitions to determine diabetes status and type based on sensitivity, specificity, positive predictive value and negative predictive value of the phenotypes against the gold standard of manually abstracted medical charts. Prevalence and incidence rates will be presented as unadjusted estimates and as race/ethnicity, sex and age-adjusted estimates using Poisson regression.

ETHICS AND DISSEMINATION

The DiCAYA Network is well positioned to advance diabetes surveillance methods. The network will disseminate EHR-based surveillance methodology that can be broadly adopted and will report diabetes prevalence and incidence for key demographic subgroups of youth and young adults in a large set of regions across the USA.

Global Longitudinal Strain as Predictor of Inducible Ischemia in No Obstructive Coronary Artery Disease in the CIAO-ISCHEMIA Study

BACKGROUND

Global longitudinal strain (GLS) is a sensitive marker for identifying subclinical myocardial dysfunction in obstructive coronary artery disease (CAD). Little is known about the relationship between GLS and ischemia in patients with myocardial ischemia and no obstructive CAD (INOCA).

OBJECTIVES

To investigate the relationship between resting GLS and ischemia on stress echocardiography (SE) in patients with INOCA.

METHODS

Left ventricular GLS was calculated offline on resting SE images at enrollment (n = 144) and 1-year follow-up (n = 120) in the CIAO-ISCHEMIA (Changes in Ischemia and Angina over One year in International Study of Comparative Health Effectiveness with Medical and Invasive Approaches trial screen failures with no obstructive CAD on computed tomography [CT] angiography) study, which enrolled participants with moderate or severe ischemia by local SE interpretation (≥3 segments with new or worsening wall motion abnormality and no obstructive (<50% stenosis) on coronary computed tomography angiography.

RESULTS

Global longitudinal strain values were normal in 83.3% at enrollment and 94.2% at follow-up. Global longitudinal strain values were not associated with a positive SE at enrollment (GLS = -21.5% positive SE vs GLS = -19.9% negative SE, P = .443) or follow-up (GLS = -23.2% positive SE vs GLS = -23.1% negative SE, P = .859). Significant change in GLS was not associated with positive SE in follow-up (P = .401). Regional strain was not associated with colocalizing ischemia at enrollment or follow-up. Changes in GLS and number of ischemic segments from enrollment to follow-up showed a modest but not clinically meaningful correlation (β = 0.41; 95% CI, 0.16, 0.67; P = .002).

CONCLUSIONS

In this cohort of INOCA patients, resting GLS values were largely normal and did not associate with the presence, severity, or location of stress-induced ischemia. These findings may suggest the absence of subclinical myocardial dysfunction detectable by echocardiographic strain analysis at rest in INOCA.

Biomarkers and cardiovascular events in patients with stable coronary disease in the ISCHEMIA Trials

IMPORTANCE

Biomarkers may improve prediction of cardiovascular events for patients with stable coronary artery disease (CAD), but their importance in addition to clinical tests of inducible ischemia and CAD severity is unknown.

OBJECTIVES

To evaluate the prognostic value of multiple biomarkers in stable outpatients with obstructive CAD and moderate or severe inducible ischemia.

DESIGN AND SETTING

The ISCHEMIA and ISCHEMIA CKD trials randomized 5,956 participants with CAD to invasive or conservative management from July 2012 to January 2018; 1,064 participated in the biorepository.

MAIN OUTCOME MEASURES

Primary outcome was cardiovascular death, myocardial infarction (MI), or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. Secondary outcome was cardiovascular death or MI. Improvements in prediction were assessed by cause-specific hazard ratios (HR) and area under the receiver operating characteristics curve (AUC) for an interquartile increase in each biomarker, controlling for other biomarkers, in a base clinical model of risk factors, left ventricular ejection fraction (LVEF) and ischemia severity. Secondary analyses were performed among patients in whom core-lab confirmed severity of CAD was ascertained by computed cardiac tomographic angiography (CCTA).

EXPOSURES

Baseline levels of interleukin-6 (IL-6), high sensitivity troponin T (hsTnT), growth differentiation factor 15 (GDF-15), N-terminal pro-B-type natriuretic peptide (NT-proBNP), lipoprotein a (Lp[a]), high sensitivity C-reactive protein (hsCRP), Cystatin C, soluble CD 40 ligand (sCD40L), myeloperoxidase (MPO), and matrix metalloproteinase 3 (MMP3).

RESULTS

Among 757 biorepository participants, median (IQR) follow-up was 3 (2-5) years, age was 67 (61-72) years, and 144 (19%) were female; 508 had severity of CAD by CCTA available. In an adjusted multimarker model with hsTnT, GDF-15, NT-proBNP and sCD40L, the adjusted HR for the primary outcome per interquartile increase in each biomarker was 1.58 (95% CI 1.22, 2.205), 1.60 (95% CI 1.16, 2.20), 1.61 (95% 1.22, 2.14), and 1.46 (95% 1.12, 1.90), respectively. The adjusted multimarker model also improved prediction compared with the clinical model, increasing the AUC from 0.710 to 0.792 (P < .01) and 0.714 to 0.783 (P < .01) for the primary and secondary outcomes, respectively. Similar findings were observed after adjusting for core-lab confirmed atherosclerosis severity.

CONCLUSIONS AND RELEVANCE

Among ISCHEMIA biorepository participants, biomarkers of myocyte injury/distension, inflammation, and platelet activity improved cardiovascular event prediction in addition to risk factors, LVEF, and assessments of ischemia and atherosclerosis severity. These biomarkers may improve risk stratification for patients with stable CAD.

Survival After Invasive or Conservative Management of Stable Coronary Disease

BACKGROUND

The ISCHEMIA trial (International Study of Comparative Health Effectiveness With Medical and Invasive Approaches) compared an initial invasive versus an initial conservative management strategy for patients with chronic coronary disease and moderate or severe ischemia, with no major difference in most outcomes during a median of 3.2 years. Extended follow-up for mortality is ongoing.

METHODS

ISCHEMIA participants were randomized to an initial invasive strategy added to guideline-directed medical therapy or a conservative strategy. Patients with moderate or severe ischemia, ejection fraction ≥35%, and no recent acute coronary syndromes were included. Those with an unacceptable level of angina were excluded. Extended follow-up for vital status is being conducted by sites or through central death index search. Data obtained through December 2021 are included in this interim report. We analyzed all-cause, cardiovascular, and noncardiovascular mortality by randomized strategy, using nonparametric cumulative incidence estimators, Cox regression models, and Bayesian methods. Undetermined deaths were classified as cardiovascular as prespecified in the trial protocol.

RESULTS

Baseline characteristics for 5179 original ISCHEMIA trial participants included median age 65 years, 23% women, 16% Hispanic, 4% Black, 42% with diabetes, and median ejection fraction 0.60. A total of 557 deaths accrued during a median follow-up of 5.7 years, with 268 of these added in the extended follow-up phase. This included a total of 343 cardiovascular deaths, 192 noncardiovascular deaths, and 22 unclassified deaths. All-cause mortality was not different between randomized treatment groups (7-year rate, 12.7% in invasive strategy, 13.4% in conservative strategy; adjusted hazard ratio, 1.00 [95% CI, 0.85-1.18]). There was a lower 7-year rate cardiovascular mortality (6.4% versus 8.6%; adjusted hazard ratio, 0.78 [95% CI, 0.63-0.96]) with an initial invasive strategy but a higher 7-year rate of noncardiovascular mortality (5.6% versus 4.4%; adjusted hazard ratio, 1.44 [95% CI, 1.08-1.91]) compared with the conservative strategy. No heterogeneity of treatment effect was evident in prespecified subgroups, including multivessel coronary disease.

CONCLUSIONS

There was no difference in all-cause mortality with an initial invasive strategy compared with an initial conservative strategy, but there was lower risk of cardiovascular mortality and higher risk of noncardiovascular mortality with an initial invasive strategy during a median follow-up of 5.7 years.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT04894877.

ISCHEMIA-EXTEND studies: Rationale and design

BACKGROUND

The ISCHEMIA and the ISCHEMIA-CKD trials found no statistical difference in the primary clinical endpoint between initial invasive management and initial conservative management of patients with chronic coronary disease and moderate to severe ischemia on stress testing without or with advanced chronic kidney disease (CKD). In ISCHEMIA, there was numerically lower cardiovascular mortality but higher non-cardiovascular mortality with no significant difference in all-cause death with an initial invasive strategy when compared with a conservative strategy. However, an invasive strategy increased peri-procedural myocardial infarction (MI) but decreased spontaneous MI with continued separation of curves over time, which potentially may lead to reduced risk of cardiovascular and all-cause mortality. Thus, the long-term effect of invasive management strategy on mortality remains unclear. In ISCHEMIA-CKD, the treatment and cause-specific mortality rates were similar during follow-up.

METHODS

Funded by the National Heart, Lung, and Blood Institute, the ISCHEMIA-EXTEND observational study is the long-term follow-up of surviving participants (projected median of 10 years) with chronic coronary disease from the ISCHEMIA trial. In the ISCHEMIA trial, 5,179 participants with moderate or severe stress-induced ischemia were randomized to initial invasive management with angiography, revascularization when feasible, and guideline-directed medical therapy (GDMT), or initial conservative management with GDMT alone and angiography reserved for failure of medical therapy. ISCHEMIA-CKD EXTEND is the long-term follow-up of surviving participants (projected median of 9 years) from the ISCHEMIA-CKD trial, a companion trial that included 777 patients with advanced CKD. Ascertainment of death will be conducted via direct participant contact, medical record review, and/or vital status registry search. The overarching objective of long-term follow-up is to assess whether there are between-group differences in long-term all-cause, cardiovascular, and non-cardiovascular mortality, and increase precision around the treatment effect estimates for risk of all-cause, cardiovascular, and non-cardiovascular mortality. We will conduct Bayesian survival modeling to take advantage of rich inferences using the posterior distribution of the treatment effect.

CONCLUSIONS

The long-term effect of an initial invasive versus conservative strategy on all-cause, cardiovascular, and non-cardiovascular mortality will be assessed. The findings of ISCHEMIA-EXTEND and ISCHEMIA-CKD EXTEND will inform patients, practitioners, practice guidelines, and health policy.

Guideline-Directed Medical Therapy Attainment and Outcomes in Dialysis-Requiring Versus Nondialysis Chronic Kidney Disease in the ISCHEMIA-CKD Trial

BACKGROUND

Patients with chronic kidney disease (CKD) on dialysis (CKD G5D) have worse cardiovascular outcomes than patients with advanced nondialysis CKD (CKD G4-5: estimated glomerular filtration rate <30 mL/[min·1.73m2]). Our objective was to evaluate the relationship between achievement of cardiovascular guideline-directed medical therapy (GDMT) goals and clinical outcomes for CKD G5D versus CKD G4-5.

METHODS

This was a subgroup analysis of ISCHEMIA-CKD (International Study of Comparative Health Effectiveness With Medical and Invasive Approaches-Chronic Kidney Disease) participants with CKD G4-5 or CKD G5D and moderate-to-severe myocardial ischemia on stress testing. Exposures included dialysis requirement at randomization and GDMT goal achievement during follow-up. The composite outcome was all-cause mortality or nonfatal myocardial infarction. Individual GDMT goal (smoking cessation, systolic blood pressure <140 mm Hg, low-density lipoprotein cholesterol <70 mg/dL, statin use, aspirin use) trajectory was modeled. Percentage point difference was estimated for each GDMT goal at 24 months between CKD G5D and CKD G4-5, and for association with key predictors. Probability of survival free from all-cause mortality or nonfatal myocardial infarction by GDMT goal achieved was assessed for CKD G5D versus CKD G4-5.

RESULTS

A total of 415 CKD G5D and 362 CKD G4-5 participants were randomized. Participants with CKD G5D were less likely to receive statin (-6.9% [95% CI, -10.3% to -3.7%]) and aspirin therapy (-3.0% [95% CI, -5.6% to -0.6%]), with no difference in other GDMT goal attainment. Cumulative exposure to GDMT achieved during follow-up was associated with reduction in all-cause mortality or nonfatal myocardial infarction (hazard ratio, 0.88 [95% CI, 0.87-0.90]; per each GDMT goal attained over 60 days), irrespective of dialysis status.

CONCLUSIONS

CKD G5D participants received statin or aspirin therapy less often. Cumulative exposure to GDMT goals achieved was associated with lower incidence of all-cause mortality or nonfatal myocardial infarction in participants with advanced CKD and chronic coronary disease, regardless of dialysis status.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT01985360.

Cardiovascular and Renal Implications of Myocardial Infarction in the ISCHEMIA-CKD Trial

BACKGROUND

ISCHEMIA-CKD (International Study of Comparative Health Effectiveness With Medical and Invasive Approaches-Chronic Kidney Disease) reported an initial invasive treatment strategy did not reduce the risk of death or nonfatal myocardial infarction (MI) compared with a conservative treatment strategy in patients with advanced chronic kidney disease, stable coronary disease, and moderate or severe myocardial ischemia. The cumulative frequency of different MI type after randomization and subsequent prognosis have not been reported.

METHODS

MI classification was based on the Third Universal Definition for MI. For procedural MI, the primary MI definition used creatine kinase-MB as the preferred biomarker, whereas the secondary MI definition used cTn (cardiac troponin); both definitions included elevated biomarker-only events with higher thresholds than nonprocedural MIs. The cumulative frequency of MI type according to treatment strategy was determined. The association of MI with subsequent all-cause death and new dialysis initiation was assessed by treating MI as a time-dependent covariate.

RESULTS

The 3-year incidence of type 1 or 2 MI with the primary MI definition was 11.2% in invasive treatment strategy and 13.6% in conservative treatment strategy (hazard ratio [HR], 0.66 [95% CI, 0.42-1.02]). Procedural MIs were more frequent in invasive treatment strategy and accounted for 9.8% and 28.3% of all MIs with the primary and secondary MI definitions, respectively. Patients had an increased risk of all-cause death after type 1 MI (adjusted HR, 4.35 [95% CI, 2.73-6.93]) and after procedural MI with the primary (adjusted HR, 2.75 [95% CI, 0.99-7.60]) and secondary MI definitions (adjusted HR, 2.91 [95% CI, 1.73-4.88]). Dialysis initiation was increased after a type 1 MI (HR, 6.45 [95% CI, 2.59-16.08]) compared with patients without an MI.

CONCLUSIONS

In ISCHEMIA-CKD, the invasive treatment strategy had higher rates of procedural MIs, particularly with the secondary MI definition, and lower rates of type 1 and 2 MIs. Procedural MIs, type 1 MIs, and type 2 MIs were associated with increased risk of subsequent death. Type 1 MI increased the risk of dialysis initiation.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT01985360.

Predictors of outcome in the ISCHEMIA-CKD trial: Anatomy versus ischemia

BACKGROUND

The ISCHEMIA-CKD (International Study of Comparative Health Effectiveness with Medical and Invasive Approaches-Chronic Kidney Disease) trial found no advantage to an invasive strategy compared to conservative management in reducing all-cause death or myocardial infarction (D/MI). However, the prognostic influence of angiographic coronary artery disease (CAD) burden and ischemia severity remains unknown in this population. We compared the relative impact of CAD extent and severity of myocardial ischemia on D/MI in patients with advanced chronic kidney disease (CKD).

METHODS

Participants randomized to invasive management with available data on coronary angiography and stress testing were included. Extent of CAD was defined by the number of major epicardial vessels with ≥50% diameter stenosis by quantitative coronary angiography. Ischemia severity was assessed by site investigators as moderate or severe using trial definitions. The primary endpoint was D/MI.

RESULTS

Of the 388 participants, 307 (79.1%) had complete coronary angiography and stress testing data. D/MI occurred in 104/307 participants (33.9%). Extent of CAD was associated with an increased risk of D/MI (P < .001), while ischemia severity was not (P = .249). These relationships persisted following multivariable adjustment. Using 0-vessel disease (VD) as reference, the adjusted hazard ratio (HR) for 1VD was 1.86, 95% confidence interval (CI) 0.94 to 3.68, P = .073; 2VD: HR 2.13, 95% CI 1.10 to 4.12, P = .025; 3VD: HR 4.00, 95% CI 2.06 to 7.76, P < .001. Using moderate ischemia as the reference, the HR for severe ischemia was 0.84, 95% CI 0.54 to 1.30, P = .427.

CONCLUSION

Among ISCHEMIA-CKD participants randomized to the invasive strategy, extent of CAD predicted D/MI whereas severity of ischemia did not.

Using Lung Base Covid-19 Findings to Predict Future Disease Trends and New Variant Outbreaks: Study of First New York City (NYC) Outbreak

RATIONALE AND OBJECTIVES

Asymptomatic COVID-19 carriers and insufficient testing make containment of the virus difficult. The purpose of this study was to determine if unexpected lung base findings on abdominopelvic CTs concerning for COVID-19 infection could serve as a surrogate for the diagnosis of COVID-19 in the community.

MATERIALS AND METHODS

A database search of abdominopelvic CT reports from March 1,2020 to May 2,2020 was performed for keywords suggesting COVID-19 infection by lung base findings. COVID-19 status, respiratory symptoms, laboratory parameters and patient outcomes (hospitalization, ICU admission and/or intubation, and death) were recorded. The trend in cases of unexpected concerning lung base findings on abdominopelvic CT at our institution was compared to the total number of confirmed new cases in NYC over the same time period.

RESULTS

The trend in abnormal lung base findings on abdominopelvic CT at our institution correlated with the citywide number of confirmed new cases, including rise and subsequent fall in total cases. The trend was not mediated by COVID-19 testing status or number of tests performed. Patients with respiratory symptoms had significantly higher ferritin (median = 995ng/ml vs 500ng/ml, p = 0.027) and death rate (8/24, 33% vs 4/54, 9%, p = 0.018) compared to those without.

CONCLUSION

The rise and fall of unexpected lung base findings suggestive of COVID-19 infection on abdominopelvic CT in patients without COVID-19 symptoms correlated with the number of confirmed new cases throughout NYC from the same time period. A model using abdominopelvic CT lung base findings can serve as a surrogate for future COVID-19 outbreaks.

Optimal medical therapy in patients with stable coronary artery disease in Poland: the ISCHEMIA trial experience

INTRODUCTION Optimal medical therapy (OMT) is the cornerstone of treatment for stable coronary disease with the ISCHEMIA trial showing similar outcomes using OMT with or without an initial invasive approach. OBJECTIVES To describe OMT goal attainment in Polish ISCHEMIA participants compared with other countries. PATIENTS AND METHODS Among 5179 trial participants, 333 were randomized in Poland. The median follow‑up was 3.2 years. OMT targets were: not smoking, high‑intensity statin therapy, low‑density lipoprotein cholesterol (LDL‑C) of less than 70 mg/dl, systolic blood pressure of less than 140 mm Hg, aspirin therapy, and ACEI / ARB, and β‑blocker therapy if indicated. RESULTS Compared with 36 other countries, at randomization, patients in Poland were older (67 [62-75] y vs 65 [58-71] y); P <0.001), more often female (30% vs 22%; P = 0.002), with a longer history of angina (3 [1-9] y vs 1 [0-3] y; P <0.001), and there were more cases of prior myocardial infarction (32% vs 18%; P <0.01) and revascularization (PCI, 40% vs 19%; CABG, 11% vs 3%; P <0.001 for both). The number of OMT goals attained increased from baseline to follow‑up visits (5 [4-5] vs 6 [5-6]; P <0.001) in Poland and other countries alike (P = 0.89 vs P = 0.14). In Poland, significant improvements were achieved regarding high‑intensity statin therapy (27% vs 50%), LDL‑C <70 mg/dl (29% vs 65%), and systolic blood pressure of less than 140 mm Hg (63% vs 81%) (P <0.001 for all), whereas not‑smoking (89% vs 89%), aspirin (90% vs 88%), ACEI / ARB (93% vs 95%), and β‑blocker therapy (94% vs 90%) remained high. CONCLUSIONS With regular surveillance and contemporary medical therapy, high OMT goal attainment was achievable among the participants of the ISCHEMIA trial in Poland relative to other countries. There is still room for improvement in LDL‑C and blood pressure management.

Outcomes of Participants With Diabetes in the ISCHEMIA Trials

BACKGROUND

Among patients with diabetes and chronic coronary disease, it is unclear if invasive management improves outcomes when added to medical therapy.

METHODS

The ISCHEMIA (International Study of Comparative Health Effectiveness with Medical and Invasive Approaches) trials (ie, ISCHEMIA and ISCHEMIA-Chronic Kidney Disease) randomized chronic coronary disease patients to an invasive (medical therapy + angiography and revascularization if feasible) or a conservative approach (medical therapy alone with revascularization if medical therapy failed). Cohorts were combined after no trial-specific effects were observed. Diabetes was defined by history, hemoglobin A1c ≥6.5%, or use of glucose-lowering medication. The primary outcome was all-cause death or myocardial infarction (MI). Heterogeneity of effect of invasive management on death or MI was evaluated using a Bayesian approach to protect against random high or low estimates of treatment effect for patients with versus without diabetes and for diabetes subgroups of clinical (female sex and insulin use) and anatomic features (coronary artery disease severity or left ventricular function).

RESULTS

Of 5900 participants with complete baseline data, the median age was 64 years (interquartile range, 57-70), 24% were female, and the median estimated glomerular filtration was 80 mL·min^-1·1.73^-2 (interquartile range, 64-95). Among the 2553 (43%) of participants with diabetes, the median percent hemoglobin A1c was 7% (interquartile range, 7-8), and 30% were insulin-treated. Participants with diabetes had a 49% increased hazard of death or MI (hazard ratio, 1.49 [95% CI, 1.31-1.70]; P<0.001). At median 3.1-year follow-up the adjusted event-free survival was 0.54 (95% bootstrapped CI, 0.48-0.60) and 0.66 (95% bootstrapped CI, 0.61-0.71) for patients with diabetes versus without diabetes, respectively, with a 12% (95% bootstrapped CI, 4%-20%) absolute decrease in event-free survival among participants with diabetes. Female and male patients with insulin-treated diabetes had an adjusted event-free survival of 0.52 (95% bootstrapped CI, 0.42-0.56) and 0.49 (95% bootstrapped CI, 0.42-0.56), respectively. There was no difference in death or MI between strategies for patients with diabetes versus without diabetes, or for clinical (female sex or insulin use) or anatomic features (coronary artery disease severity or left ventricular function) of patients with diabetes.

CONCLUSIONS

Despite higher risk for death or MI, chronic coronary disease patients with diabetes did not derive incremental benefit from routine invasive management compared with initial medical therapy alone. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01471522.

Kidney Transplant List Status and Outcomes in the ISCHEMIA-CKD Trial

BACKGROUND

Patients with chronic kidney disease (CKD) and coronary artery disease frequently undergo preemptive revascularization before kidney transplant listing.

OBJECTIVES

In this post hoc analysis from ISCHEMIA-CKD (International Study of Comparative Health Effectiveness of Medical and Invasive Approaches-Chronic Kidney Disease), we compared outcomes of patients not listed versus those listed according to management strategy.

METHODS

In the ISCHEMIA-CKD trial (n = 777), 194 patients (25%) with chronic coronary syndromes and at least moderate ischemia were listed for transplant. The primary (all-cause mortality or nonfatal myocardial infarction) and secondary (death, nonfatal myocardial infarction, hospitalization for unstable angina, heart failure, resuscitated cardiac arrest, or stroke) outcomes were analyzed using Cox multivariable modeling. Heterogeneity of randomized treatment effect between listed versus not listed groups was assessed.

RESULTS

Compared with those not listed, listed patients were younger (60 years vs 65 years), were less likely to be of Asian race (15% vs 29%), were more likely to be on dialysis (83% vs 44%), had fewer anginal symptoms, and were more likely to have coronary angiography and coronary revascularization irrespective of treatment assignment. Among patients assigned to an invasive strategy versus conservative strategy, the adjusted hazard ratios for the primary outcome were 0.91 (95% confidence interval [CI]: 0.54-1.54) and 1.03 (95% CI: 0.78-1.37) for those listed and not listed, respectively (pinteraction= 0.68). Adjusted hazard ratios for secondary outcomes were 0.89 (95% CI: 0.55-1.46) in listed and 1.17 (95% CI: 0.89-1.53) in those not listed (pinteraction = 0.35).

CONCLUSIONS

In ISCHEMIA-CKD, an invasive strategy in kidney transplant candidates did not improve outcomes compared with conservative management. These data do not support routine coronary angiography or revascularization in patients with advanced CKD and chronic coronary syndromes listed for transplant. (ISCHEMIA-Chronic Kidney Disease Trial [ISCHEMIA-CKD]; NCT01985360).

Natural History of Patients with Ischemia and No Obstructive Coronary Artery Disease: The CIAO-ISCHEMIA Study

Background: Ischemia with no obstructive coronary artery disease (INOCA) is common and has an adverse prognosis. We set out to describe the natural history of symptoms and ischemia in INOCA. Methods: CIAO-ISCHEMIA (Changes in Ischemia and Angina over One year in ISCHEMIA trial screen failures with INOCA) was an international cohort study conducted from 2014-2019 involving angina assessments (Seattle Angina Questionnaire [SAQ]) and stress echocardiograms 1-year apart. This was an ancillary study that included patients with history of angina who were not randomized in the ISCHEMIA trial. Stress-induced wall motion abnormalities were determined by an echocardiographic core laboratory blinded to symptoms, coronary artery disease (CAD) status and test timing. Medical therapy was at the discretion of treating physicians. The primary outcome was the correlation between changes in SAQ Angina Frequency score and change in echocardiographic ischemia. We also analyzed predictors of 1-year changes in both angina and ischemia, and compared CIAO participants with ISCHEMIA participants with obstructive CAD who had stress echocardiography before enrollment, as CIAO participants did. Results: INOCA participants in CIAO were more often female (66% of 208 vs. 26% of 865 ISCHEMIA participants with obstructive CAD, p<0.001), but the magnitude of ischemia was similar (median 4 ischemic segments [IQR 3-5] both groups). Ischemia and angina were not significantly correlated at enrollment in CIAO (p=0.46) or ISCHEMIA stress echocardiography participants (p=0.35). At 1 year, the stress echocardiogram was normal in half of CIAO participants and 23% had moderate or severe ischemia (≥3 ischemic segments). Angina improved in 43% and worsened in 14%. Change in ischemia over one year was not significantly correlated with change in angina (rho=0.029). Conclusions:Improvement in ischemia and improvement in angina were common in INOCA, but not correlated. Our INOCA cohort had a similar degree of inducible wall motion abnormalities to concurrently enrolled ISCHEMIA participants with obstructive CAD. Our results highlight the complex nature of INOCA pathophysiology and the multifactorial nature of angina. Clinical Trial Registration: URL: https://clinicaltrials.gov Unique Identifier: NCT02347215.

Accelerated single-shot T2-weighted fat-suppressed (FS) MRI of the liver with deep learning-based image reconstruction: qualitative and quantitative comparison of image quality with conventional T2-weighted FS sequence

OBJECTIVE

To compare the image quality of an accelerated single-shot T2-weighted fat-suppressed (FS) MRI of the liver with deep learning-based image reconstruction (DL HASTE-FS) with conventional T2-weighted FS sequence (conventional T2 FS) at 1.5 T.

METHODS

One hundred consecutive patients who underwent clinical MRI of the liver at 1.5 T including the conventional T2-weighted fat-suppressed sequence (T2 FS) and accelerated single-shot T2-weighted MRI of the liver with deep learning-based image reconstruction (DL HASTE-FS) were included. Images were reviewed independently by three blinded observers who used a 5-point confidence scale for multiple measures regarding the artifacts and image quality. Descriptive statistics and McNemar's test were used to compare image quality scores and percentage of lesions detected by each sequence, respectively. Intra-class correlation coefficient (ICC) was used to assess consistency in reader scores.

RESULTS

Acquisition time for DL HASTE-FS was 51.23 +/ 10.1 s, significantly (p < 0.001) shorter than conventional T2-FS (178.9 ± 85.3 s). DL HASTE-FS received significantly higher scores than conventional T2-FS for strength and homogeneity of fat suppression; sharpness of liver margin; sharpness of intra-hepatic vessel margin; in-plane and through-plane respiratory motion; other ghosting artefacts; liver-fat contrast; and overall image quality (all, p < 0.0001). DL HASTE-FS also received higher scores for lesion conspicuity and sharpness of lesion margin (all, p < .001), without significant difference for liver lesion contrast (p > 0.05).

CONCLUSIONS

Accelerated single-shot T2-weighted MRI of the liver with deep learning-based image reconstruction showed superior image quality compared to the conventional T2-weighted fat-suppressed sequence despite a 4-fold reduction in acquisition time.

KEY POINTS

• Conventional fat-suppressed T2-weighted sequence (conventional T2 FS) can take unacceptably long to acquire and is the most commonly repeated sequence in liver MRI due to motion. • DL HASTE-FS demonstrated superior image quality, improved respiratory motion and other ghosting artefacts, and increased lesion conspicuity with comparable liver-to-lesion contrast compared to conventional T2FS sequence. • DL HASTE- FS has the potential to replace conventional T2 FS sequence in routine clinical MRI of the liver, reducing the scan time, and improving the image quality.

Characteristics of the built environment and spatial patterning of type 2 diabetes in the urban core of Durham, North Carolina

BACKGROUND

Few studies examine relationships between built environment (BE) and type 2 diabetes mellitus (T2DM) using spatial models, investigate BE domains apart from food environment or physical activity resources or conduct sensitivity analysis of methodological choices made in measuring BE. We examine geographic heterogeneity of T2DM, describe how heterogeneity in T2DM relates to BE and estimate associations of T2DM with BE.

METHODS

Individual-level electronic health records (n=41 203) from the Duke Medicine Enterprise Data Warehouse (2007-2011) were linked to BE based on census block. Data on housing damage, property disorder, territoriality, vacancy and public nuisances were used to estimate BE based on four different construction methods (CMs). We used race-stratified aspatial and spatial Bayesian models to assess geographic heterogeneity in T2DM and associations of T2DM with BE.

RESULTS

Among whites, a 1 SD increase in poor quality BE was associated with a 1.03 (95% credible interval 1.01 to 1.06) and 1.06 (95 % credible interval 1.02 to 1.11) increased risk of T2DM for poor quality BE CM1 and CM2, respectively. Among blacks/African Americans, associations between T2DM and BE overlapped with the null for all CMs. The addition of BE to white models reduced residual geographic heterogeneity in T2DM by 4%-15%, depending on CM. In black/African-American models, BE did not affect residual heterogeneity.

CONCLUSION

Associations of T2DM with BE were sensitive to CM and geographic heterogeneity in T2DM differed by race/ethnicity. Findings underscore the need to consider multiple methods of estimating BE and consider differences in relationships by race/ethnicity.

Residential Racial Isolation and Spatial Patterning of Type 2 Diabetes Mellitus in Durham, North Carolina

Neighborhood characteristics such as racial segregation may be associated with type 2 diabetes mellitus, but studies have not examined these relationships using spatial models appropriate for geographically patterned health outcomes. We constructed a local, spatial index of racial isolation (RI) for black residents in a defined area, measuring the extent to which they are exposed only to one another, to estimate associations of diabetes with RI and examine how RI relates to spatial patterning in diabetes. We obtained electronic health records from 2007-2011 from the Duke Medicine Enterprise Data Warehouse. Patient data were linked to RI based on census block of residence. We used aspatial and spatial Bayesian models to assess spatial variation in diabetes and relationships with RI. Compared with spatial models with patient age and sex, residual geographic heterogeneity in diabetes in spatial models that also included RI was 29% and 24% lower for non-Hispanic white and black residents, respectively. A 0.20-unit increase in RI was associated with an increased risk of diabetes for white (risk ratio = 1.24, 95% credible interval: 1.17, 1.31) and black (risk ratio = 1.07, 95% credible interval: 1.05, 1.10) residents. Improved understanding of neighborhood characteristics associated with diabetes can inform development of policy interventions.

A retrospective cohort study to quantify the contribution of health systems to child survival in Kenya: 1996-2014

Globally, the majority of childhood deaths in the post-neonatal period are caused by infections that can be effectively treated or prevented with inexpensive interventions delivered through even very basic health facilities. To understand the role of inadequate health systems on childhood mortality in Kenya, we assemble a large, retrospective cohort of children (born 1996–2013) and describe the health systems context of each child using health facility survey data representative of the province at the time of a child’s birth. We examine the relationship between survival beyond 59 months of age and geographic distribution of health facilities, quality of services, and cost of services. We find significant geographic heterogeneity in survival that can be partially explained by differences in distribution of health facilities and user fees. Higher per capita density of health facilities resulted in a 25% reduction in the risk of death (HRR = 0.73, 95% CI:0.58 to 0.91) and accounted for 30% of the between-province heterogeneity in survival. User fees for sick-child visits increased risk by 30% (HRR = 1.30, 95% CI:1.11 to 1.53). These results implicate health systems constraints in child mortality, quantify the contribution of specific domains of health services, and suggest priority areas for improvement to accelerate reductions in child mortality.

Racial isolation and exposure to airborne particulate matter and ozone in understudied US populations: Environmental justice applications of downscaled numerical model output

BACKGROUND

Researchers and policymakers are increasingly focused on combined exposures to social and environmental stressors, especially given how often these stressors tend to co-locate. Such exposures are equally relevant in urban and rural areas and may accrue disproportionately to particular communities or specific subpopulations.

OBJECTIVES

To estimate relationships between racial isolation (RI), a measure of the extent to which minority racial/ethnic group members are exposed to only one another, and long-term particulate matter with an aerodynamic diameter of <2.5μ (PM2.5) and ozone (O3) levels in urban and nonurban areas of the eastern two-thirds of the US.

METHODS

Long-term (5year average) census tract-level PM2.5 and O3 concentrations were calculated using output from a downscaler model (2002-2006). The downscaler uses a linear regression with additive and multiplicative bias coefficients to relate ambient monitoring data with gridded output from the Community Multi-scale Air Quality (CMAQ) model. A local, spatial measure of RI was calculated at the tract level, and tracts were classified by urbanicity, RI, and geographic region. We examined differences in estimated pollutant exposures by RI, urbanicity, and demographic subgroup (e.g., race/ethnicity, education, socioeconomic status, age), and used linear models to estimate associations between RI and air pollution levels in urban, suburban, and rural tracts.

RESULTS

High RI tracts (≥80th percentile) had higher average PM2.5 levels in each category of urbanicity compared to low RI tracts (<20th percentile), with the exception of the rural West. Patterns in O3 levels by urbanicity and RI differed by region. Linear models indicated that PM2.5 concentrations were significantly and positively associated with RI. The largest association between PM2.5 and RI was observed in the rural Midwest, where a one quintile increase in RI was associated with a 0.90μg/m(3) (95% confidence interval: 0.83, 0.99μg/m(3)) increase in PM2.5 concentration. Associations between O3 and RI in the Northeast, Midwest and West were positive and highest in suburban and rural tracts, even after controlling for potential confounders such as percentage in poverty.

CONCLUSION

RI is associated with higher 5year estimated PM2.5 concentrations in urban, suburban, and rural census tracts, adding to evidence that segregation is broadly associated with disparate air pollution exposures. Disproportionate burdens to adverse exposures such as air pollution may be a pathway to racial/ethnic disparities in health.

Implications of construction method and spatial scale on measures of the built environment

Background

Research surrounding the built environment (BE) and health has resulted in inconsistent findings. Experts have identified the need to examine methodological choices, such as development and testing of BE indices at varying spatial scales. We sought to examine the impact of construction method and spatial scale on seven measures of the BE using data collected at two time points.

Methods

The Children’s Environmental Health Initiative conducted parcel-level assessments of 57 BE variables in Durham, NC (parcel N = 30,319). Based on a priori defined variable groupings, we constructed seven mutually exclusive BE domains (housing damage, property disorder, territoriality, vacancy, public nuisances, crime, and tenancy). Domain-based indices were developed according to four different index construction methods that differentially account for number of parcels and parcel area. Indices were constructed at the census block level and two alternative spatial scales that better depict the larger neighborhood context experienced by local residents: the primary adjacency community and secondary adjacency community. Spearman’s rank correlation was used to assess if indices and relationships among indices were preserved across methods.

Results

Territoriality, public nuisances, and tenancy were weakly to moderately preserved across methods at the block level while all other indices were well preserved. Except for the relationships between public nuisances and crime or tenancy, and crime and housing damage or territoriality, relationships among indices were poorly preserved across methods. The number of indices affected by construction method increased as spatial scale increased, while the impact of construction method on relationships among indices varied according to spatial scale.

Conclusions

We found that the impact of construction method on BE measures was index and spatial scale specific. Operationalizing and developing BE measures using alternative methods at varying spatial scales before connecting to health outcomes allows researchers to better understand how methodological decisions may affect associations between health outcomes and BE measures. To ensure that associations between the BE and health outcomes are not artifacts of methodological decisions, researchers would be well-advised to conduct sensitivity analysis using different construction methods. This approach may lead to more robust results regarding the BE and health outcomes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12942-016-0044-x) contains supplementary material, which is available to authorized users.

Associations of birth outcomes with maternal polybrominated diphenyl ethers and thyroid hormones during pregnancy

BACKGROUND

Previous research has linked polybrominated diphenyl ether (PBDE) exposure to poor birth outcomes and altered thyroid hormone levels.

OBJECTIVES

We examined whether maternal PBDE serum levels were associated with infant birth weight (g), head circumference (cm), birth length (cm), and birth weight percentile for gestational age. We explored the potential for a mediating role of thyroid hormone levels.

METHODS

During 2008-2010, we recruited 140 pregnant women in their third trimester as part of a larger clinical obstetrics study known as Healthy Pregnancy, Healthy Baby. Blood samples were collected during a routine prenatal clinic visit. Serum was analyzed for PBDEs, phenolic metabolites, and thyroid hormones. Birth outcome information was abstracted from medical records.

RESULTS

In unadjusted models, a two-fold increase in maternal BDE 153 was associated with an average decrease in head circumference of 0.32cm (95% CI: -0.53, -0.12); however, this association was attenuated after control for maternal risk factors. BDE 47 and 99 were similarly negatively associated but with 95% confidence intervals crossing the null. Associations were unchanged in the presence of thyroid hormones.

CONCLUSIONS

Our data suggest a potential deleterious association between maternal PBDE levels and infant head circumference; however, confirmatory studies are needed in larger sample sizes. A mediating role of thyroid hormones was not apparent.

Effects of maternal prenatal smoking and birth outcomes extending into the normal range on academic performance in fourth grade in North Carolina, USA

BACKGROUND

Research has documented the adverse relationship of child cognitive development with maternal prenatal smoking and poor birth outcomes. The potential, however, for maternal prenatal smoking to modify the association between birth outcomes and cognitive development is unclear.

METHODS

We linked statewide North Carolina birth data for non-Hispanic white and non-Hispanic black children to end-of-grade test scores in reading and mathematics at fourth grade (n = 65 677). We fit race-stratified multilevel models of test scores regressed on maternal smoking, birth outcomes (as measured by continuous and categorical gestational age and birthweight percentile for gestational age), and their interaction, controlling for maternal- and child-level socio-economic factors.

RESULTS

Smoking was consistently associated with decrements in test scores, and better birth outcomes were associated with improvements in test scores, even in clinically normal ranges. Test scores increased quadratically with improving birth outcomes among smoking and non-smoking mothers. Among non-Hispanic white children, the magnitude of the association between gestational age and test scores was larger for children whose mothers smoked during pregnancy compared with the non-smoking group. However, among non-Hispanic black children, birth outcomes did not appear to interact with maternal smoking on test scores.

CONCLUSIONS

Maternal prenatal smoking may interact with birth outcomes on reading and mathematics test scores, particularly among non-Hispanic white children. Improvements in birth outcomes, even within the clinically normal range, may be associated with improved academic performance. Pregnancy-related exposures and events exert a significant and long-term impact on cognitive development.

Association of autism with induced or augmented childbirth in North Carolina Birth Record (1990-1998) and Education Research (1997-2007) databases

IMPORTANCE

One in 88 children in the United States is diagnosed as having autism spectrum disorder. Significant interest centers on understanding the environmental factors that may contribute to autism risk.

OBJECTIVE

To examine whether induced (stimulating uterine contractions prior to the onset of spontaneous labor) and/or augmented (increasing the strength, duration, or frequency of uterine contractions with spontaneous onset of labor) births are associated with increased odds of autism.

DESIGN, SETTING, AND PARTICIPANTS

We performed an epidemiological analysis using multivariable logistic regression modeling involving the North Carolina Detailed Birth Record and Education Research databases. The study featured 625,042 live births linked with school records, including more than 5500 children with a documented exceptionality designation for autism.

EXPOSURES

Induced or augmented births.

MAIN OUTCOMES AND MEASURES

Autism as assessed by exceptionality designations in child educational records.

RESULTS

Compared with children born to mothers who received neither labor induction nor augmentation, children born to mothers who were induced and augmented, induced only, or augmented only experienced increased odds of autism after controlling for potential confounders related to socioeconomic status, maternal health, pregnancy-related events and conditions, and birth year. The observed associations between labor induction/augmentation were particularly pronounced in male children.

CONCLUSIONS AND RELEVANCE

Our work suggests that induction/augmentation during childbirth is associated with increased odds of autism diagnosis in childhood. While these results are interesting, further investigation is needed to differentiate among potential explanations of the association including underlying pregnancy conditions requiring the eventual need to induce/augment, the events of labor and delivery associated with induction/augmentation, and the specific treatments and dosing used to induce/augment labor (e.g., exogenous oxytocin and prostaglandins).

The built environment and childhood obesity in Durham, North Carolina

The relationship between childhood obesity and aspects of the built environment characterizing neighborhood social context is understudied. This study evaluates the association between 7 built environment domains and childhood obesity in Durham, North Carolina. Measures of housing damage, property disorder, vacancy, nuisances, and territoriality were constructed using data from a 2008 community assessment. Renter-occupied housing and crime measures were developed from public databases. The authors linked these measures to 2008-2009 Duke University Medical Center pediatric preventive care visits. Age- and sex-specific body mass index percentiles were used to classify children as normal weight (>5th and ≤85th percentile), overweight (>85th and ≤95th percentile), or obese (>95th percentile). Ordinal logistic regression models with cluster-corrected standard errors evaluated the association between weight status and the built environment. Adjusting for child-level socioeconomic characteristics, nuisances and crime were associated with childhood overweight/obesity (P < .05). Built environment characteristics appear important to childhood weight status in Durham, North Carolina.

A spatial bivariate probit model for correlated binary data with application to adverse birth outcomes

Motivated by a study examining geographic variation in birth outcomes, we develop a spatial bivariate probit model for the joint analysis of preterm birth and low birth weight. The model uses a hierarchical structure to incorporate individual and areal-level information, as well as spatially dependent random effects for each spatial unit. Because rates of preterm birth and low birth weight are likely to be correlated within geographic regions, we model the spatial random effects via a bivariate conditionally autoregressive prior, which induces regional dependence between the outcomes and provides spatial smoothing and sharing of information across neighboring areas. Under this general framework, one can obtain region-specific joint, conditional, and marginal inferences of interest. We adopt a Bayesian modeling approach and develop a practical Markov chain Monte Carlo computational algorithm that relies primarily on easily sampled Gibbs steps. We illustrate the model using data from the 2007–2008 North Carolina Detailed Birth Record.

Seasonality of poor pregnancy outcomes in North Carolina

BACKGROUND

Seasonal variation in poor pregnancy outcomes has not received the same level of research attention and rigor as has the well-established seasonal variation in births.

METHODS

In this analysis of data from the 2001-2005 North Carolina Detailed Birth Record, we use season of conception as a proxy for environmental or other risk factors. We model the continuous pregnancy outcome of birth weight percentile for gestational age by use of linear regression. We use logistic regression to model the binary pregnancy outcomes of low birth weight (< 2500 g), preterm birth (< 37 weeks), and small for gestational age (< 10th percentile of birth weight for gestational age).

RESULTS

We found significant seasonal patterns in poor pregnancy outcomes. Our results suggest that, in North Carolina, seasonal patterns are most pronounced among non-Hispanic white women living in urban areas.

LIMITATIONS

The present study is limited by the restricted set of maternal and pregnancy variables available in this data set. Richer data, potentially including psychosocial and activity measures of the women, would allow us to more ably discern what is driving the seasonal patterns we observed. The pronounced increased risk associated with a spring season of conception provides an important clue for determining the true causative factors.

CONCLUSIONS

Poor pregnancy outcomes in North Carolina follow a clear seasonal pattern based on timing of conception, with patterns most pronounced among non-Hispanic white women living in urban areas. These seasonal patterns are suggestive of causative environmental factors and certainly warrant additional research.

Associations between polybrominated diphenyl ether (PBDE) flame retardants, phenolic metabolites, and thyroid hormones during pregnancy

BACKGROUND

Polybrominated diphenyl ethers (PBDEs) are chemical additives used as flame retardants in commercial products. PBDEs are bioaccumulative and persistent and have been linked to several adverse health outcomes.

OBJECTIVES

This study leverages an ongoing pregnancy cohort to measure PBDEs and PBDE metabolites in serum collected from an understudied population of pregnant women late in their third trimester. A secondary objective was to determine whether the PBDEs or their metabolites were associated with maternal thyroid hormones.

METHODS

One hundred forty pregnant women > 34 weeks into their pregnancy were recruited into this study between 2008 and 2010. Blood samples were collected during a routine prenatal clinic visit. Serum was analyzed for a suite of PBDEs, three phenolic metabolites (i.e., containing an -OH moiety), and five thyroid hormones.

RESULTS

PBDEs were detected in all samples and ranged from 3.6 to 694 ng/g lipid. Two hydroxylated BDE congeners (4´-OH-BDE 49 and 6-OH-BDE 47) were detected in > 67% of the samples. BDEs 47, 99, and 100 were significantly and positively associated with free and total thyroxine (T4) levels and with total triiodothyronine levels above the normal range. Associations between T4 and PBDEs remained after controlling for smoking status, maternal age, race, gestational age, and parity.

CONCLUSIONS

PBDEs and OH-BDEs are prevalent in this cohort, and levels are similar to those in the general population. Given their long half-lives, PBDEs may be affecting thyroid regulation throughout pregnancy. Further research is warranted to determine mechanisms through which PBDEs affect thyroid hormone levels in developing fetuses and newborn babies.

A geospatial analysis of the effects of aviation gasoline on childhood blood lead levels

BACKGROUND

Aviation gasoline, commonly referred to as avgas, is a leaded fuel used in small aircraft. Recent concern about the effects of lead emissions from planes has motivated the U.S. Environmental Protection to consider regulating leaded avgas.

OBJECTIVE

In this study we investigated the relationship between lead from avgas and blood lead levels in children living in six counties in North Carolina.

METHODS

We used geographic information systems to approximate areas surrounding airports in which lead from avgas may be present in elevated concentrations in air and may also be deposited to soil. We then used regression analysis to examine the relationship between residential proximity to airports and North Carolina blood lead surveillance data in children 9 months to 7 years of age while controlling for factors including age of housing, socioeconomic characteristics, and seasonality.

RESULTS

Our results suggest that children living within 500 m of an airport at which planes use leaded avgas have higher blood lead levels than other children. This apparent effect of avgas on blood lead levels was evident also among children living within 1,000 m of airports. The estimated effect on blood lead levels exhibited a monotonically decreasing dose-response pattern, with the largest impact on children living within 500 m.

CONCLUSIONS

We estimated a significant association between potential exposure to lead emissions from avgas and blood lead levels in children. Although the estimated increase was not especially large, the results of this study are nonetheless directly relevant to the policy debate surrounding the regulation of leaded avgas.

A spatial measure of neighborhood level racial isolation applied to low birthweight, preterm birth, and birthweight in North Carolina

Research on racial residential segregation (RRS) and birth outcomes has focused on RRS at a broad geographic scale, in an aspatial framework, and in northern US cities. We developed a spatial measure of neighborhood level racial isolation of blacks. We examined the association between this new measure and low birthweight, preterm birth, and birthweight in the southern state of North Carolina. Natality data were obtained from the North Carolina Detailed Birth Record 1998-2002 files. Using multiple regression with cluster corrected standard errors, infants born to black and white mothers living in black isolated neighborhoods had, on average, decreased birthweight, and increased odds of low birthweight and preterm birth compared to their counterparts in less isolated areas. White mothers in predominantly black neighborhoods experienced greater increases in odds of each poor birth outcome than did black mothers. Black isolation may be proxying concentrated socioeconomic disadvantage, including disamenities in the built environment.