Low hourly wages in middle‐age are associated with faster memory decline in older age: Evidence from the health and retirement study

Alzheimer s & Dementia · 2023-06-01

Abstract Background Little research has investigated the long‐term relationship between low wages and memory decline, despite the growing share of low‐wage workers in the US labor market. We examined whether cumulative exposure to low wages over 12 years in midlife is associated with memory decline in later life. Method We used 1992‐2016 data from the Health and Retirement Study, a biennial longitudinal survey of nationally representative samples of Americans aged 50+. We analyzed data from 3,803 individuals born 1936‐1941 using confounder‐adjusted linear mixed‐effects models. Low‐wage was defined as hourly wage lower than two‐thirds of the federal median wage for the corresponding year. Low‐wage exposure history was categorized into ‘never’, ‘intermittent’, and ‘sustained’ based on wages earned from 1992 to 2004. Memory function was measured at each visit from 2004 to 2016 by a memory composite score; on average, participants completed 4.8 memory assessments from 2004‐2016. Estimates were obtained in the total sample and within strata of sex (N males = 1,913, N females = 1,890). Result At the beginning of cognitive follow‐up (2004) our sample was on average 65 years old with a mean memory score of 1.15 standard units. The confounder‐adjusted annual rate of memory decline among workers who never earned low wages was ‐0.12 standard units, 95% CI: [‐0.14, ‐0.10]. Compared with this, memory decline among workers with sustained earning of low midlife wages was significantly faster (β time*sustained :‐0.012, 95% CI: [‐0.02, ‐0.01]), corresponding to an annual rate of ‐0.13 standard units for this group. Put into terms of “excess cognitive aging”, the cognitive aging experienced by workers with sustained exposure to low midlife wages over a 10‐year period is what workers never earning low‐wages would experience in 11 years. Similar associations were found among males and females. No significant association between intermittent earning of low wages and memory decline was observed. Conclusion Sustained earning of low wages in midlife was significantly associated with a downward trajectory of memory performance in older age. Enhancing social policies to protect low‐wage workers (e.g., increasing minimum wage) may be especially beneficial for the cognitive health of individuals with sustained low‐wage employment in midlife.

Depressive symptoms mediate the relationship between sustained food insecurity and cognition: a causal mediation analysis

Annals of Epidemiology · 2023 · 8 citations

• Medicine
• Demography
• Environmental health

Regression discontinuity design to evaluate the effect of statins on myocardial infarction in electronic health records

European Journal of Epidemiology · 2023-03-20 · 3 citations

Propensity Scores in Health Disparities Research: The Example of Cognitive Aging and the Hispanic Paradox

Epidemiology · 2023-03-28 · 4 citations

BACKGROUND: Individuals of Mexican ancestry in the United States experience substantial socioeconomic disadvantages compared with non-Hispanic white individuals; however, some studies show these groups have similar dementia risk. Evaluating whether migration selection factors (e.g., education) associated with risk of Alzheimer disease and related dementia (ADRD) explain this paradoxical finding presents statistical challenges. Intercorrelation of risk factors, common with social determinants, could make certain covariate patterns very likely or unlikely to occur for particular groups, which complicates their comparison. Propensity score (PS) methods could be leveraged here to diagnose nonoverlap and help balance exposure groups. METHODS: We compare conventional and PS-based methods to examine differences in cognitive trajectories between foreign-born Mexican American, US-born Mexican American, and US-born non-Hispanic white individuals in the Health and Retirement Study (1994-2018). We examined cognition using a global measure. We estimated trajectories of cognitive decline from linear mixed models adjusted for migration selection factors also associated with ADRD risk conventionally or with inverse probability weighting. We also employed PS trimming and match weighting. RESULTS: In the full sample, where PS overlap was poor, unadjusted analyses showed both Mexican ancestry groups had worse baseline cognitive scores but similar or slower rates of decline compared with non-Hispanic white adults; adjusted findings were similar, regardless of method. Focusing analyses on populations where PS overlap was improved (PS trimming and match weighting) did not alter conclusions. CONCLUSIONS: Attempting to equalize groups on migration selection and ADRD risk factors did not explain paradoxical findings for Mexican ancestry groups in our study.

Association of Low Hourly Wages in Middle Age With Faster Memory Decline in Older Age: Evidence From the Health and Retirement Study

American Journal of Epidemiology · 2022 · 15 citations

• Demography
• Medicine
• Gerontology

Little research has investigated the long-term relationship between low wages and memory decline, despite the growing share of low-wage workers in the US labor market. Here, we examined whether cumulative exposure to low wages over 12 years in midlife is associated with memory decline in later life. Using 1992-2016 data from the Health and Retirement Study, we analyzed data from 2,879 individuals born in 1936-1941 using confounder-adjusted linear mixed-effects models. Low-wage work was defined as an hourly wage lower than two-thirds of the federal median wage for the corresponding year and was categorized into "never," "intermittent," and "sustained" based on wages earned from 1992 to 2004. Memory function was measured at each study visit from 2004 to 2016 via a memory composite score. The confounder-adjusted annual rate of memory decline among "never" low-wage earners was -0.12 standard units (95% confidence interval: -0.13, -0.10). Compared with this, memory decline among workers with sustained earning of low midlife wages was significantly faster (βtime×sustained = -0.014, 95% confidence interval: -0.02, -0.01), corresponding to an annual rate of -0.13 standard units for this group. Sustained low-wage earning in midlife was significantly associated with a downward trajectory of memory performance in older age. Enhancing social policies to protect low-wage workers may be especially beneficial for their cognitive health.

Regression discontinuity design to evaluate the effect of statins on myocardial infarction in electronic health records

medRxiv · 2022-04-06

ABSTRACT Regression discontinuity design (RDD) is a quasi-experimental method intended for causal inference in observational settings. While RDD is gaining popularity in clinical studies, there are limited real-world studies examining the performance of this approach on estimating known trial-established casual effects. The goal of this paper is to estimate the effects of statins on myocardial infarction (MI) using RDD and propensity score matching. For the regression discontinuity analysis, we leveraged a 2008 guideline in the UK that recommends statins if a patient’s 10-year cardiovascular disease (CVD) risk score >20%. We used UK electronic health record data from the Health Improvement Network on 49,242 patients aged 65+ in 2008-2011 (our study baseline) without a history of CVD and no statin use in the year prior to the CVD risk score assessment. Both the regression discontinuity (n=19,432) and the propensity score matched populations (n=24,814) demonstrated good balance of confounders. Using RDD, the adjusted point estimate for statins on MI was in the protective direction and similar to the statin effect observed in clinical trials, although the confidence interval included the null (HR= 0.8, 95%CI: 0.4, 1.4). Conversely, the adjusted estimates using propensity score matching remained in the harmful direction: HR =2.4 (95%CI:2.0, 3.0). Regression discontinuity appeared superior to propensity score matching in replicating the known protective association of statins with MI, although precision was poor. Our findings suggest that, when used appropriately, regression discontinuity can expand the scope of clinical investigations aimed at causal inference by leveraging treatment rules from everyday clinical practice.

Body mass index in early adulthood and dementia in late life: Findings from a pooled cohort

Alzheimer s & Dementia · 2021 · 36 citations

• Medicine
• Gerontology
• Demography

INTRODUCTION: To examine the independent association of body mass index (BMI) in early adulthood with dementia incidence among men and women. METHODS: We studied 5104 older adults from the Cardiovascular Health Study (CHS) and the Health, Aging, and Body Composition (Health ABC) study. We imputed early adulthood and midlife BMI using a pooled parent cohort with complete adult lifespan coverage and previously established methods. Dementia was ascertained using criteria such as neuropsychological test battery, medical records, and dementia-related drug use. Pooled logistic regression (PLR) models were used. RESULTS: Compared to women with normal BMI in early adulthood, the odds of dementia were higher among both overweight (odds ratio [OR] = 1.8; 95% confidence interval [CI] = 1.31 to 2.54) and obese (OR = 2.45; 95% CI = 1.47 to 4.06) women, independent of mid- and late-life BMI. Similar relationship was observed in men. CONCLUSIONS: With the growing obesity epidemic among US adults, efforts aimed at reducing dementia may need to begin obesity prevention and treatment early in the life course.

Association of early life BMI with dementia risk: Findings from a pooled cohort analysis

Alzheimer s & Dementia · 2020-12-01

Abstract Background The evidence about the timing and influence of some key cardiovascular risk factors, such as Body Mass Index (BMI), on the risk of Alzheimer disease and other dementias remains debatable. Studies have shown that high midlife BMI increases the risk of dementia, while high late life BMI may be protective; however, relatively little is known about the role of early life BMI on the risk of Alzheimer Disease and other dementias. Method We studied 5,104 older adults from two studies, the Cardiovascular Health Study (CHS, n=2,909) and the Health, Aging and Body Composition study (Health ABC, n=2,195) study. For CHS‐Health ABC older adults, we imputed early and midlife BMI, beginning at age 18, using linear mixed models applied to a pooled cohort which also included young and middle‐aged adults from CARDIA and MESA. BMI was then summarized by time‐weighted averages in early (ages 20‐49), mid (ages 50‐69), and late life (ages 70‐89). In CHS, dementia was adjudicated by an expert committee following a detailed neuropsychological test battery and neurological examination. In Health ABC, dementia diagnosis was determined based on hospitalization ICD codes, dementia‐related drugs and decline on the Modified Mini Mental State Examination. All analyses were sex stratified. Result CHS‐Health ABC participants had a mean age of 72.6 years (SD=4.2) at enrollment, 18% were black and 56% were women. For women, dementia risk increased with higher early life BMI: it was 1.8 times higher among those who were overweight (OR=1.8; 95% CI=1.31‐2.54) and 2.5 times higher among those who were obese (OR=2.45; 95% CI=1.47‐4.06), from pooled logistic regression models adjusted for midlife and late life BMI. For men, dementia risk increased with higher early life (Obese OR=2.47; 95% CI=1.46‐4.19) and mid life BMI (Overweight OR=1.51; 95% CI=1.11‐2.05 and Obese OR=2.00; 95% CI=1.16‐3.42), in models also adjusted for late life BMI. For both women and men, dementia risk decreased with higher late life BMI. Conclusion Our study is the first to report heightened dementia risk with higher early life BMI, for both women and men. Accounting for early life BMI, we found no effect for midlife BMI on dementia risk among women.