Implications of Lifecourse Epidemiology for Research on Determinants of Adult Disease

Many diseases commonly associated with aging are now thought to have social and physiologic antecedents in early life. Understanding how the timing of exposure to early life risk factors influences later-life health may illuminate mechanisms driving adult health inequalities and identify possible points for effective interventions. Recognizing chronic diseases as developing across the lifecourse also has implications for the conduct of research on adult risk factors for disease. We review alternative conceptual models that describe how the timing of risk factor exposure relates to the development of disease. We propose some expansions of lifecourse models to improve their relevance for research on adult chronic disease, using the relationship between education and adult cognitive decline and dementia as an example. We discuss the important implications each of the lifecourse conceptual models has on study design, analysis, and interpretation of research on aging and chronic diseases. We summarize several research considerations implied by the lifecourse framework, including: advantages of analyzing change in function rather than onset of impairment; the pervasive challenge of survivor bias; the importance of controlling for possible confounding by early life conditions; and the likely heterogeneity in responses of adults to treatment

Does schooling attained by adult children affect parents' psychosocial well-being in later life? Using Mexico's 1993 compulsory schooling law as a quasi-experiment

Higher adult child educational attainment may benefit older parents' psychosocial well-being in later life. This may be particularly important in low- and middle-income countries, where recent generations have experienced comparatively large increases in educational attainment. We used data from the 2012 Mexican Health and Aging Study, a nationally representative study of adults aged ≥50 years and leveraged the exogenous variation in adult child education induced by Mexico's compulsory schooling law passed in 1993. We employed two-stage least squares (2SLS) regression to estimate the effects of increased schooling among adult children on parents' (respondents') depressive symptoms and life satisfaction scores, controlling for demographic and socioeconomic characteristics. We considered heterogeneity by parent and child gender and other sociodemographic characteristics. Our study included 7186 participants with an average age of 60.1 years; 54.9% were female. In the 2SLS analyses, increased schooling among oldest adult children was associated with fewer depressive symptoms (β = −0.25; 95% CI: −0.51, 0.00) but no difference in life satisfaction (β = 0.01; 95% CI: −0.22, 0.25). Stratified models indicated differences in the magnitude of association with depressive symptoms for mothers (β = −0.27, 95% CI: −0.56, 0.01) and fathers (β = −0.18, 95% CI: −0.63, 0.26) and when considering increased schooling of oldest sons (β = −0.37; 95% CI: −0.73, −0.02) and daughters (β = −0.05, 95% CI: −0.23, 0.13). No parent and child gender differences were found for life satisfaction. Power was limited to detect heterogeneity across other sociodemographic characteristics in the second stage although first-stage estimates were larger for urban (vs. rural) dwelling and more (vs. less) highly educated respondents. Results were similar when considering the highest educated child as well as increased schooling across all children. Our findings suggest that longer schooling among current generations of adult children, particularly sons, may benefit their older parents' psychosocial well-being

Alternative causal inference methods in population health research: Evaluating tradeoffs and triangulating evidence.

Population health researchers from different fields often address similar substantive questions but rely on different study designs, reflecting their home disciplines. This is especially true in studies involving causal inference, for which semantic and substantive differences inhibit interdisciplinary dialogue and collaboration. In this paper, we group nonrandomized study designs into two categories: those that use confounder-control (such as regression adjustment or propensity score matching) and those that rely on an instrument (such as instrumental variables, regression discontinuity, or differences-in-differences approaches). Using the Shadish, Cook, and Campbell framework for evaluating threats to validity, we contrast the assumptions, strengths, and limitations of these two approaches and illustrate differences with examples from the literature on education and health. Across disciplines, all methods to test a hypothesized causal relationship involve unverifiable assumptions, and rarely is there clear justification for exclusive reliance on one method. Each method entails trade-offs between statistical power, internal validity, measurement quality, and generalizability. The choice between confounder-control and instrument-based methods should be guided by these tradeoffs and consideration of the most important limitations of previous work in the area. Our goals are to foster common understanding of the methods available for causal inference in population health research and the tradeoffs between them; to encourage researchers to objectively evaluate what can be learned from methods outside one's home discipline; and to facilitate the selection of methods that best answer the investigator's scientific questions

Type of High-School Credentials and Older Age ADL and IADL Limitations: Is the GED Credential Equivalent to a Diploma?

Purpose: Educational attainment is a robust predictor of disability in elderly Americans: older adults with high-school (HS) diplomas have a substantially lower disability than individuals who did not complete HS. General Educational Development (GED) diplomas now comprise almost 20% of new HS credentials issued annually in the United States but it is unknown whether the apparent health advantages of HS diplomas extend to GED credentials. This study examines whether adults older than 50 years with GEDs have higher odds of incident instrumental or basic activities of daily living (IADLs) limitations compared with HS degree holders. Methods: We compared odds of incident IADL limitations by HS credential type using discrete-time survival models among 9,426 Health and Retirement Study participants followed from 1998 through 2008. Results: HS degree holders had lower odds of incident IADLs than GED holders (OR = 0.72, 95% CI = 0.58, 0.90 and OR = 0.69, 95% CI = 0.56, 0.86 for ADLs and IADLs, respectively). There was no significant difference in odds of incident IADL limitations between GED holders and respondents without HS credentials (OR = 0.89, 95% CI = 0.71, 1.11 for ADLs; OR = 0.88, 95% CI = 0.70, 1.12 for IADLs).Implications: Although GEDs are widely accepted as equivalent to high school diplomas, they are not associated with comparable health advantages for physical limitations in older age

Childhood adversity and asthma prevalence: evidence from 10 US states (2009–2011)

Background: Existing evidence on stress and asthma prevalence has disproportionately focused on pregnancy and postpregnancy early life stressors, largely ignoring the role of childhood adversity as a risk factor. Childhood adversity (neglect, stressful living conditions and maltreatment) may influence asthma prevalence through mechanisms on the hypothalamic-pituitary axis. Methods: Data from the Center for Disease Control's (CDC's) Behavioral Risk Factor Surveillance System (BRFSS) surveys were used to examine cross-sectional associations of adverse childhood experiences (ACE) with lifetime and current asthma prevalence. Information on childhood adversity was available from 84 786 adult respondents in 10 US states. Poisson regression models (with robust SE) were used to estimate prevalence ratios (PRs) relating overall ACE score and dimensions of exposure ACE to asthma prevalence, adjusting for socioeconomic status. Results: Greater ACE was associated with a higher prevalence of asthma (adjusted PRcat 4=1.78 (95% CI 1.69 to 1.87), adjusted PRcat 1=1.21 (95% CI 1.16 to 1.27)). Reported experiences of sexual abuse (adjusted PR=1.48* (1.42 to 1.55)) and physical abuse (adjusted PR=1.38* (1.33 to 1.43)) were associated with a higher asthma prevalence. No clear socioeconomic gradient was noted, but those reporting lowest education and income levels reported high rates of asthma and adversity. Sensitivity analyses indicated that ACE exposures were interrelated. Conclusions: Report of childhood adversity predicts asthma prevalence among US adults. Frameworks for asthma prevention need to recognise and integrate aspects related to childhood adversity. Further investigation into specific time periods of exposure would provide meaningful inferences for interventions

Comparison of existing methods for algorithmic classification of dementia in the Health and Retirement Study

Background: Dementia ascertainment is difficult and costly, hindering the use of large, representative studies such as the Health and Retirement Study (HRS) to monitor trends or disparities in dementia. To address this issue, multiple groups of researchers have developed algorithms to classify dementia status in HRS participants using data from HRS and the Aging, Demographics, and Memory Study (ADAMS), an HRS sub-study that systematically ascertained dementia status. However, the relative performance of each algorithm has not been systematically evaluated. Objective: To compare the performance of five existing algorithms, overall and by sociodemographic subgroups. Methods: We created two standardized datasets: (a) training data (N=786, i.e. ADAMS Wave A and corresponding HRS data, which was used previously to create the algorithms) and (b) validation data (N=530, i.e. ADAMS Waves B, C, and D and corresponding HRS data which was not used previously to create the algorithms). In both, we used each algorithm to classify HRS participants as demented or not demented and compared the algorithmic diagnoses to the ADAMS diagnoses. Results: In the training data, overall classification accuracies ranged from 80% to 87%, sensitivity ranged from 53% to 90%, and specificity ranged from 79% to 96% across the five algorithms. Though overall classification accuracy was similar in the validation data (range: 79% to 88%), sensitivity was much lower (range: 17% to 61%), while specificity was higher (range: 82% to 98%) compared to the training data. Classification accuracy was generally worse in non-Hispanic blacks (range: 68% to 85%) and Hispanics (range: 65% to 88%), compared to non-Hispanic whites (range: 79% to 88%). Across datasets, sensitivity was generally higher for proxy-respondents, while specificity (and overall accuracy) was higher for self-respondents. Conclusions: Worse sensitivity in the validation dataset may suggest either overfitting or that the algorithms are better at identifying prevalent versus incident dementia, while differences in performance across algorithms suggest that the usefulness of each will vary depending on the user’s purpose. Further planned work will evaluate algorithm performance in external validation datasets

Historical Differences in School Term Length and Measured Blood Pressure: Contributions to Persistent Racial Disparities among US- Born Adults

IntroductionLegally mandated segregation policies dictated significant differences in the educational experiences of black and white Americans through the first half of the 20th century, with markedly lower quality in schools attended by black children. We determined whether school term length, a common marker of school quality, was associated with blood pressure and hypertension among a cohort of older Americans who attended school during the de jure segregation era.MethodsNational Health and Nutrition Examination Survey I and II data were linked to state-level historical information on school term length. We used race and gender-stratified linear regression models adjusted for age, state, and year of birth to estimate effects of term length on systolic and diastolic blood pressure (SBP and DBP) and hypertension for US-born adults. We also tested whether correcting years of schooling for term length differences attenuated estimated racial disparities.ResultsAmong black women, 10% longer school term was associated with lower SBP, DBP, and hypertension prevalence (2.1 mmHg, 1.0 mmHg, and 5.0 percentage points respectively). Associations for whites and for black men were not statistically significant. Adjustment for education incorporating corrections for differences in school term length slightly attenuated estimated racial disparities.ConclusionsLonger school term length predicted better BP outcomes among black women, but not black men or whites