Associations Between Midlife Menopausal Hormone Therapy Use, Incident Diabetes, and Late Life Memory in the Wisconsin Longitudinal Study

BACKGROUND

Prior research suggests a link between menopausal hormone therapy (MHT) use, memory function, and diabetes risk. The menopausal transition is a modifiable period to enhance long-term health and cognitive outcomes, although studies have been limited by short follow-up periods precluding a solid understanding of the lasting effects of MHT use on cognition.

OBJECTIVE

We examined the effects of midlife MHT use on subsequent diabetes incidence and late life memory performance in a large, same-aged, population-based cohort. We hypothesized that the beneficial effects of MHT use on late life cognition would be partially mediated by reduced diabetes risk.

METHODS

1,792 women from the Wisconsin Longitudinal Study (WLS) were included in analysis. We employed hierarchical linear regression, Cox regression, and causal mediation models to test the associations between MHT history, diabetes incidence, and late life cognitive performance.

RESULTS

1,088/1,792 women (60.7%) reported a history of midlife MHT use and 220/1,792 (12.3%) reported a history of diabetes. MHT use history was associated with better late life immediate recall (but not delayed recall), as well as a reduced risk of diabetes with protracted time to onset. Causal mediation models suggest that the beneficial effect of midlife MHT use on late life immediate recall were at least partially mediated by diabetes risk.

CONCLUSION

Our data support a beneficial effect of MHT use on late life immediate recall (learning) that was partially mediated by protection against diabetes risk, supporting MHT use in midlife as protective against late life cognitive decline and adverse health outcomes.

GENDER, MARITAL STATUS, AND COGNITIVE HEALTH IN LATE LIFE: IS MARRIAGE MORE PROTECTIVE FOR MEN?

While marital status appears to be protective for one's health, there is also evidence of gender differences in its protective influence. In short, men appear to differentially benefit from marriage compared to women. A growing body of work on later life cognitive functioning and dementia also finds protective effects for those who are married. But there is less evidence as to whether those patterns differ by gender. Using the Wisconsin Longitudinal Study, a nearly full life course longitudinal study, we find evidence that while there are no differences for men, married women, as compared to their unmarried counterparts, have lower levels of cognitive functioning at ~age 80. Differences in underlying health, educational attainment, and adolescent cognitive functioning do not explain the pattern. Similar to broader health, women do not appear to benefit from marriage in late life. Indeed, we find evidence of cognitive benefits of being single for older women.

Genetic diversity fuels gene discovery for tobacco and alcohol use

Tobacco and alcohol use are heritable behaviours associated with 15% and 5.3% of worldwide deaths, respectively, due largely to broad increased risk for disease and injury1-4. These substances are used across the globe, yet genome-wide association studies have focused largely on individuals of European ancestries5. Here we leveraged global genetic diversity across 3.4 million individuals from four major clines of global ancestry (approximately 21% non-European) to power the discovery and fine-mapping of genomic loci associated with tobacco and alcohol use, to inform function of these loci via ancestry-aware transcriptome-wide association studies, and to evaluate the genetic architecture and predictive power of polygenic risk within and across populations. We found that increases in sample size and genetic diversity improved locus identification and fine-mapping resolution, and that a large majority of the 3,823 associated variants (from 2,143 loci) showed consistent effect sizes across ancestry dimensions. However, polygenic risk scores developed in one ancestry performed poorly in others, highlighting the continued need to increase sample sizes of diverse ancestries to realize any potential benefit of polygenic prediction.

Black-White variation in the relationship between early educational experiences and trajectories of cognitive function among US-born older adults

Black adults face a substantially higher risk for dementia in later life compared to their White peers. Given the critical role of educational attainment and cognitive function in later life dementia risk, this paper aims to determine if early educational experiences and educational attainment are differentially related to trajectories of cognitive status across race and if this further varies by education cohort. We use data from the Life History Mail Survey (LHMS) and prospective data on cognition from the Health and Retirement Study (HRS). We restrict our sample to Black and White US-born adults who provided at least one measure of cognitive status from 1995/6–2016. We find evidence of Black-White differences in the association between educational experiences and level of cognitive function, episodic memory, and working memory, but little evidence of Black-White differences in these associations with decline. Having a learning problem was associated with lower levels of cognitive function, episodic memory, and working memory for White and Black older adults, but was more strongly related to these outcomes among Black older adults. Further, the Black-White difference in this association was generally found in older cohorts that completed schooling after enactment of federal policies that improved educational resources for children with learning disabilities. Attending racially discordant schools was positively associated with level of these cognitive outcomes for Black older adults but not for White older adults. We also find that the educational gradient in level of cognitive function was larger for Black compared to White older adults in older cohorts not benefiting from the Brown v Board of Education decision but was similar for Black and White older adults attending school in the post-Brown era.

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Black adults are twice as likely to have dementia than White adults.

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The roots of this risk are poorly understood but may be due to educational experiences.

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Three educational experiences differentially predicted cognitive status by race.

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These included having a learning problem, desegregated schooling, and attainment.

How difficult should it be? Evidence of burden tolerance from a nationally representative sample

There is growing attention to how policymakers and bureaucrats think about administrative burdens, but we know less about public tolerance for burdens. We examine public burden tolerance in two major programmes (Medicaid and SNAP) using a representative sample of US residents. We show broad support for work requirements and weaker support for generally making it difficult to access benefits. People with conservative beliefs, greater opposition to social policies, and higher income are more tolerant of burdens in social policies. Those who have personal experience of welfare policies are less tolerant of burdens.

Polygenic prediction of educational attainment within and between families from genome-wide association analyses in 3 million individuals

We conduct a genome-wide association study (GWAS) of educational attainment (EA) in a sample of ~3 million individuals and identify 3,952 approximately uncorrelated genome-wide-significant single-nucleotide polymorphisms (SNPs). A genome-wide polygenic predictor, or polygenic index (PGI), explains 12-16% of EA variance and contributes to risk prediction for ten diseases. Direct effects (i.e., controlling for parental PGIs) explain roughly half the PGI's magnitude of association with EA and other phenotypes. The correlation between mate-pair PGIs is far too large to be consistent with phenotypic assortment alone, implying additional assortment on PGI-associated factors. In an additional GWAS of dominance deviations from the additive model, we identify no genome-wide-significant SNPs, and a separate X-chromosome additive GWAS identifies 57.

Effect of childhood proximity to lead mining on late life cognition

INTRODUCTION

Lead exposure negatively affects cognitive functioning among children. However, there is limited evidence about whether exposure to lead in early life impairs later life cognitive functioning.

METHODS

Participants in the prospective Wisconsin Longitudinal Study cohort (N = 8583) were linked to the 1940 Census, which was taken when they were young children. We estimated the effect of living near a lead mine in childhood on late life memory/attention and language/executive function in 2004 (mean age 64) and 2011 (mean age 71).

RESULTS

Lead-exposed children had significantly steeper memory/attention decline between 2004 and 2011 and worse language/executive function at baseline in late life. These long-term effects of lead were not mediated through adolescent IQ or late life SES and health factors.

DISCUSSION

Proximity to lead mining in childhood had long-term effects on late life memory/attention decline and language/executive function, reflecting a possible latent influence of lead exposure. More research is needed to understand behavioral and biological pathways underlying this relationship.

Using sibling models to unpack the relationship between education and cognitive functioning in later life

As the population ages and the prevalence of dementia increases, unpacking robust and persistent associations between educational attainment and later life cognitive functioning is increasingly important. We do know, from studies with robust causal designs, that policies that increase years of schooling improve later life cognitive functioning. Yet these studies don't illuminate why older adults with greater educational attainment have relatively preserved cognitive functioning. Studies focused on why, however, have been hampered by methodological limitations and inattention to some key explanations for this relationship. Consequently, we test explanations encompassing antecedent factors, specifically family environments, adolescent IQ, and genetic factors, as well as adult mediating mechanisms, specifically health behaviors and health. We employ the Wisconsin Longitudinal Study, which includes 80 years of prospectively collected data on a sample of 1 in every 3 high school graduates, and a selected sibling, from the class of 1957. Sibling models, and the inclusion of prospectively collected early and midlife covariates, allows us to address the explanatory and methodological limitations of the prior literature to better unpack the relationship between education and later life cognitive functioning. We find little evidence that early life genetic endowments and environments, or midlife health and health behaviors, explain the relationship. Adolescent cognition, however, does matter; higher educational attainment, linked to antecedent adolescent cognitive functioning, helps protect against lower levels of cognitive functioning in later life. Both adolescent cognition and education, however, independently associate with later life cognitive functioning at relatively similar magnitudes. Educational attainment's relationship to later life cognitive functioning is not simply a function of adolescent cognitive functioning.

WLS-ILIAD: Initial Lifetime’s Impact on ADRD

Between 2021 and 2025, WLS will collect two new waves of data, which will capture detailed measures of cognitive change and dementia as the cohort reaches their early to mid 80s. In this session, I will provide an overview of the data that we’re collecting, as well as opportunities to explore early and mid-life determinants of cognitive change and dementia onset in this unique study. Compared to existing studies, the WLS offers some novel opportunities. First, it will provide one of the only opportunities to study how early and midlife life conditions and experiences, on data gathered prospectively, can shape cognitive trajectories and dementia in later life. Second, its unique sibling design provides significant analytic advantages, improving causal inference. Third, the study includes a large group of rural participants, allowing for closer examinations of how rural conditions may shape risk and resilience against cognitive decline and dementia in later life.

WLS-ILIAD: New Longitudinal Resource for Cognitive and Dementia Data

One of the distinctive strengths of WLS is the availability of Henmon-Nelson IQ scores on all participants while in high school, followed by prospective collection of data through cognitive batteries of varying size and sophistication. Launched in 1993, the initial longitudinal cognitive testing included 8 abstract reasoning items followed by the administration of larger cognitive batteries in 2004 and 2011 comprised of a 10-item word recall test, digit ordering task, phonemic and category fluency, as well as repeated and new items from the WAIS-R similarities task first administered in the 1993 survey. In 2018, with R01 funding from NIA, the scope of cognitive testing expanded significantly and includes administration of a phone-based cognitive screening measure, and a comprehensive in-person neuropsychological assessment for individuals identified at risk for dementia targeting a range of cognitive domains, including memory, language, attention, visuospatial abilities, and executive functioning.

Making Medicare Complicated: The Consequences of Privatization

Starting with policy changes in the 1980s, Medicare has largely become privatized, with nearly 40 percent of beneficiaries enrolled in private Medicare Advantage plans and another 30 percent with private supplemental coverage, including for prescription drug coverage. As a result, Medicare has become laden with administrative burdens and barriers. Beneficiaries are faced with a confusing array of plans and coverage options when they enroll, and are expected to choose a new plan every year. The choice they make has large implications for their health care costs, as well as their actual access to health care. While we typically think that targeted policies are burdensome and social insurance programs are accessible, Medicare contradicts this easy categorization. Instead, it demonstrates how private sector involvement in public programs can increase complexity and increase burdens for beneficiaries.

Resource profile and user guide of the Polygenic Index Repository

Polygenic indexes (PGIs) are DNA-based predictors. Their value for research in many scientific disciplines is growing rapidly. As a resource for researchers, we used a consistent methodology to construct PGIs for 47 phenotypes in 11 datasets. To maximize the PGIs' prediction accuracies, we constructed them using genome-wide association studies-some not previously published-from multiple data sources, including 23andMe and UK Biobank. We present a theoretical framework to help interpret analyses involving PGIs. A key insight is that a PGI can be understood as an unbiased but noisy measure of a latent variable we call the 'additive SNP factor'. Regressions in which the true regressor is this factor but the PGI is used as its proxy therefore suffer from errors-in-variables bias. We derive an estimator that corrects for the bias, illustrate the correction, and make a Python tool for implementing it publicly available.

Reconstructing Sociogenomics Research: Dismantling Biological Race and Genetic Essentialism Narratives

We detail the implications of sociogenomics for social determinants research. We focus on education and race because of how early twentieth-century scientific eugenic thinking facilitated a range of racist and eugenic policies, most of which helped justify and pattern racial and educational morbidity and mortality disparities that remain today, and are central to sociological research. Consequently, we detail the implications of sociogenomics research by unpacking key controversies and opportunities in sociogenomics as they pertain to the understanding of racial and educational inequalities. We clarify why race is not a valid biological or genetic construct, the ways that environments powerfully shape genetic influence, and risks linked to this field of research. We argue that sociologists can usefully engage in genetics research, a domain dominated by psychologists and behaviorists who, given their focus on individuals, have mostly not examined the role of history and social structure in shaping genetic influence.

Genome-wide meta-analysis of muscle weakness identifies 15 susceptibility loci in older men and women

Low muscle strength is an important heritable indicator of poor health linked to morbidity and mortality in older people. In a genome-wide association study meta-analysis of 256,523 Europeans aged 60 years and over from 22 cohorts we identify 15 loci associated with muscle weakness (European Working Group on Sarcopenia in Older People definition: n = 48,596 cases, 18.9% of total), including 12 loci not implicated in previous analyses of continuous measures of grip strength. Loci include genes reportedly involved in autoimmune disease (HLA-DQA1 p = 4 × 10-17), arthritis (GDF5 p = 4 × 10-13), cell cycle control and cancer protection, regulation of transcription, and others involved in the development and maintenance of the musculoskeletal system. Using Mendelian randomization we report possible overlapping causal pathways, including diabetes susceptibility, haematological parameters, and the immune system. We conclude that muscle weakness in older adults has distinct mechanisms from continuous strength, including several pathways considered to be hallmarks of ageing.

Does Rural Living in Early Life Increase the Risk for Reduced Cognitive Functioning in Later Life?

BACKGROUND

There is a robust consensus, most recently articulated in the 2020 Lancet Commission, that the roots of dementia can be traced to early life, and that the path to prevention may start there as well. Indeed, a growing body of research demonstrates that early life disadvantage may influence the risk for later life dementia and cognitive decline. A still understudied risk, however, is early life rural residence, a plausible pathway given related economic and educational disadvantages, as well as associations between later life rural living and lower levels of cognitive functioning.

OBJECTIVE

We aim to examine whether living in rural environments during early life has long term implications for cognitive health in later life.

METHODS

We employed the Wisconsin Longitudinal Study, which tracked 1 in every 3 high school graduates from the class of 1957, from infancy to ∼age 72. The data include a rich array of prospectively collected early life data, unique among existing studies, as well as later life measures of cognitive functioning.

RESULTS

We found a robust relationship between early life rural residence, especially living on a farm, and long-term risk for reduced cognitive performance on recall and fluency tasks. Controls for adolescent cognitive functioning, APOEɛ2 and APOEɛ4, as well as childhood and adult factors, ranging from early life socioeconomic conditions to later life health and rural and farm residency, did not alter the findings.

CONCLUSION

Rural living in early life is an independent risk for lower levels of cognitive functioning in later life.

Assessing Dementia Prevalence in the Wisconsin Longitudinal Study: Cohort Profile, Protocol, and Preliminary Findings

BACKGROUND

There is growing consensus that non-genetic determinants of dementia can be linked to various risk- and resiliency-enhancing factors accumulating throughout the lifespan, including socioeconomic conditions, early life experiences, educational attainment, lifestyle behaviors, and physical/mental health. Yet, the causal impact of these diverse factors on dementia risk remain poorly understood due to few longitudinal studies prospectively characterizing these influences across the lifespan.

OBJECTIVE

The Initial Lifespan's Impact on Alzheimer's Disease and Related Dementia (ILIAD) study aims to characterize dementia prevalence in the Wisconsin Longitudinal Study (WLS), a 60-year longitudinal study documenting life course trajectories of educational, family, occupational, psychological, cognitive, and health measures.

METHODS

Participants are surveyed using the modified Telephone Interview for Cognitive Status (TICS-m) to identify dementia risk. Those scoring below cutoff undergo home-based neuropsychological, physical/neurological, and functional assessments. Dementia diagnosis is determined by consensus panel and merged with existing WLS data for combined analysis.

RESULTS

Preliminary findings demonstrate the initial success of the ILIAD protocol in detecting dementia prevalence in the WLS. Increasing age, hearing issues, lower IQ, male sex, APOE4 positivity, and a steeper annualized rate of memory decline assessed in the prior two study waves, all increased likelihood of falling below the TICS-m cutoff for dementia risk. TICS-m scores significantly correlated with standard neuropsychological performance and functional outcomes.

CONCLUSION

We provide an overview of the WLS study, describe existing key lifespan variables relevant to studies of dementia and cognitive aging, detail the current WLS-ILIAD study protocol, and provide a first glimpse of preliminary study findings.

Privatizing the Welfare State

The growth of the private sector in the Medicare and Medicaid programs is a sea change, leading many to argue that the old age welfare state is effectively becoming privatized. I examine these trends, but focus on the consequences for how older adults experience their interactions with government. In particular, I examine how privatization increases administrative burden for beneficiaries. Older adults must navigate hundreds of choices, leading to significant confusion. Most fail to pick policies that maximize their benefits and reduce their cost. This confusion harms beneficiaries. They end up with suboptimal coverage, with increased out of pocket costs and decreased access to care. The confusion, however, generates profits for insurers. Part of a symposium sponsored by the Women's Issues Interest Group.

Policy-Relevant Research and Media Communication

The second speaker is Dr. Pamela Herd, Professor of Public Policy at Georgetown University. Dr. Herd will discuss her approach to conducting innovative and impactful policy-relevant research, as well as her experience communicating research to policymakers and the public through op-eds and other forms of media. Dr. Herd’s research focuses on inequality and how it intersects with health, aging, and policy. She also has expertise in survey methods and administration. Her most recent book, Administrative Burden, was reviewed in the New York Review of Books. She has also published editorials in venues such as the New York Times and the Washington Post, as well as podcasts, including the Weeds, produced by Vox media.

Gut bacterial taxonomic abundances vary with cognition, personality, and mood in the Wisconsin Longitudinal Study

Animal studies have shown that the gut microbiome can influence memory, social behavior, and anxiety-like behavior. Several human studies show similar results where variation in the gut microbiome is associated with dementia, depression, and personality traits, though most of these studies are limited by small sample size and other biases. Here, we analyzed fecal samples from 313 participants in the Wisconsin Longitudinal Study, a randomly selected population-based cohort of older adults, with measured psycho-cognitive dimensions (cognition, mood, and personality) and key confounders. 16s V4 sequencing showed that Megamonas is associated with all measured psycho-cognitive traits, Fusobacterium is associated with cognitive and personality traits, Pseudoramibacter_Eubacterium is associated with mood and personality traits, Butyvibrio is associated with cognitive traits, and Cloacibacillus is associated with mood traits. These findings are robust to sensitivity analyses and provide novel evidence of shared relationships between the gut microbiome and multiple psycho-cognitive traits in older adults, confirming some of the animal literature, while also providing new insights. While we addressed some of the weaknesses in prior studies, further studies are necessary to elucidate temporal and causal relationships between the gut microbiome and multiple psycho-cognitive traits in well-phenotyped, randomly-selected population-based samples.

The gut microbiome and psycho-cognitive traits

The idea that trillions of bacteria inhabit our gut is somewhat unnerving, yet these bacteria may have a greater influence on our behavior than previously thought. Accumulating data strongly suggest that these gut commensal organisms have a strong inter-relationship with our brain and behavior, including cognitive function, mood, and personality. In this chapter, we discuss the role of the gut microbiome in the development of human personality, mood and mood disorders, and cognition, with a particular emphasis on the current consensus and controversies in the literature surrounding the behavioral effects of bioactive metabolites, microbial ratio shifts, and neurotransmitter synthesis facilitated by the microbiome.

Human Capital and Administrative Burden: The Role of Cognitive Resources in Citizen-State Interactions

One means by which the state reinforces inequality is by imposing administrative burdens that loom larger for citizens with lower levels of human capital. Integrating insights from various disciplines, this article focuses on one aspect of human capital: cognitive resources. The authors outline a model that explains how burdens and cognitive resources, especially executive functioning, interrelate. The article then presents illustrative examples, highlighting three common life factors-scarcity, health problems, and age-related cognitive decline. These factors create a human capital catch-22, increasing people's likelihood of needing state assistance while simultaneously undermining the cognitive resources required to negotiate the burdens they encounter while seeking such assistance. The result is to reduce access to state benefits and increase inequality. The article concludes by calling for scholars of behavioral public administration and public administration more generally to incorporate more attention to human capital into their research.

GROWING UP ON A FARM AND COGNITIVE FUNCTIONING IN LATER LIFE

There is growing interest in rural disadvantage and the implications for health and well-being in later life. We examine the relationship between living in rural areas in childhood and cognitive outcomes later in life using the Wisconsin Longitudinal Study. The WLS has prospective childhood measures of geographic status, adolescent IQ, and detailed measures of socioeconomic status, combined with later life measures of health and cognitive functioning. We find a robust relationship between rurality and lower levels of cognitive functioning, but it is explained by growing up on a farm.

Sick Individuals and Sick (Microbial) Populations: Challenges in Epidemiology and the Microbiome

The human microbiome represents a new frontier in understanding the biology of human health. While epidemiology in this area is still in its infancy, its scope will likely expand dramatically over the coming years. To rise to the challenge, we argue that epidemiology should capitalize on its population perspective as a critical complement to molecular microbiome research, allowing for the illumination of contextual mechanisms that may vary more across populations rather than among individuals. We first briefly review current research on social context and the gut microbiome, focusing specifically on socioeconomic status (SES) and race/ethnicity. Next, we reflect on the current state of microbiome epidemiology through the lens of one specific area, the association of the gut microbiome and metabolic disorders. We identify key methodological shortcomings of current epidemiological research in this area, including extensive selection bias, the use of noncompositionally robust measures, and a lack of attention to social factors as confounders or effect modifiers.

Social and population health science approaches to understand the human microbiome

The microbiome is now considered our 'second genome' with potentially comparable importance to the genome in determining human health. There is, however, a relatively limited understanding of the broader environmental factors, particularly social conditions, that shape variation in human microbial communities. Fulfilling the promise of microbiome research - particularly the microbiome's potential for modification - will require collaboration between biologists and social and population scientists. For life scientists, the plasticity and adaptiveness of the microbiome calls for an agenda to understand the sensitivity of the microbiome to broader social environments already known to be powerful predictors of morbidity and mortality. For social and population scientists, attention to the microbiome may help answer nagging questions about the underlying biological mechanisms that link social conditions to health. We outline key substantive and methodological advances that can be made if collaborations between social and population health scientists and life scientists are strategically pursued.

Genetic analysis of social-class mobility in five longitudinal studies

A summary genetic measure, called a "polygenic score," derived from a genome-wide association study (GWAS) of education can modestly predict a person's educational and economic success. This prediction could signal a biological mechanism: Education-linked genetics could encode characteristics that help people get ahead in life. Alternatively, prediction could reflect social history: People from well-off families might stay well-off for social reasons, and these families might also look alike genetically. A key test to distinguish biological mechanism from social history is if people with higher education polygenic scores tend to climb the social ladder beyond their parents' position. Upward mobility would indicate education-linked genetics encodes characteristics that foster success. We tested if education-linked polygenic scores predicted social mobility in >20,000 individuals in five longitudinal studies in the United States, Britain, and New Zealand. Participants with higher polygenic scores achieved more education and career success and accumulated more wealth. However, they also tended to come from better-off families. In the key test, participants with higher polygenic scores tended to be upwardly mobile compared with their parents. Moreover, in sibling-difference analysis, the sibling with the higher polygenic score was more upwardly mobile. Thus, education GWAS discoveries are not mere correlates of privilege; they influence social mobility within a life. Additional analyses revealed that a mother's polygenic score predicted her child's attainment over and above the child's own polygenic score, suggesting parents' genetics can also affect their children's attainment through environmental pathways. Education GWAS discoveries affect socioeconomic attainment through influence on individuals' family-of-origin environments and their social mobility.

Gene discovery and polygenic prediction from a genome-wide association study of educational attainment in 1.1 million individuals

Here we conducted a large-scale genetic association analysis of educational attainment in a sample of approximately 1.1 million individuals and identify 1,271 independent genome-wide-significant SNPs. For the SNPs taken together, we found evidence of heterogeneous effects across environments. The SNPs implicate genes involved in brain-development processes and neuron-to-neuron communication. In a separate analysis of the X chromosome, we identify 10 independent genome-wide-significant SNPs and estimate a SNP heritability of around 0.3% in both men and women, consistent with partial dosage compensation. A joint (multi-phenotype) analysis of educational attainment and three related cognitive phenotypes generates polygenic scores that explain 11-13% of the variance in educational attainment and 7-10% of the variance in cognitive performance. This prediction accuracy substantially increases the utility of polygenic scores as tools in research.

Fecal Aliquot Straw Technique (FAST) allows for easy and reproducible subsampling: assessing interpersonal variation in trimethylamine-N-oxide (TMAO) accumulation

BACKGROUND

Convenient, reproducible, and rapid preservation of unique biological specimens is pivotal to their use in microbiome analyses. As an increasing number of human studies incorporate the gut microbiome in their design, there is a high demand for streamlined sample collection and storage methods that are amenable to different settings and experimental needs. While several commercial kits address collection/shipping needs for sequence-based studies, these methods do not preserve samples properly for studies that require viable microbes.

RESULTS

We describe the Fecal Aliquot Straw Technique (FAST) of fecal sample processing for storage and subsampling. This method uses a straw to collect fecal material from samples recently voided or preserved at low temperature but not frozen (i.e., 4 °C). Different straw aliquots collected from the same sample yielded highly reproducible communities as disclosed by 16S rRNA gene sequencing; operational taxonomic units that were lost, or gained, between the two aliquots represented very low-abundance taxa (i.e., < 0.3% of the community). FAST-processed samples inoculated into germ-free animals resulted in gut communities that retained on average ~ 80% of the donor's bacterial community. Assessment of choline metabolism and trimethylamine-N-oxide accumulation in transplanted mice suggests large interpersonal variation.

CONCLUSIONS

Overall, FAST allows for repetitive subsampling without thawing of the specimens and requires minimal supplies and storage space, making it convenient to utilize both in the lab and in the field. FAST has the potential to advance microbiome research through easy, reproducible sample processing.

The Influence of Social Conditions Across the Life Course on the Human Gut Microbiota: A Pilot Project With the Wisconsin Longitudinal Study

Objective

To test the feasibility of collecting and integrating data on the gut microbiome into one of the most comprehensive longitudinal studies of aging and health, the Wisconsin Longitudinal Study (WLS). The long-term goal of this integration is to clarify the contribution of social conditions in shaping the composition of the gut microbiota late in life. Research on the microbiome, which is considered to be of parallel importance to human health as the human genome, has been hindered by human studies with nonrandomly selected samples and with limited data on social conditions over the life course.

Methods

No existing population-based longitudinal study had collected fecal specimens. Consequently, we created an in-person protocol to collect stool specimens from a subgroup of WLS participants.

Results

We collected 429 stool specimens, yielding a 74% response rate and one of the largest human samples to date.

Discussion

The addition of data on the gut microbiome to the WLS-and to other population based longitudinal studies of aging-is feasible, under the right conditions, and can generate innovative research on the relationship between social conditions and the gut microbiome.

Human longevity: 25 genetic loci associated in 389,166 UK biobank participants

We undertook a genome-wide association study (GWAS) of parental longevity in European descent UK Biobank participants. For combined mothers' and fathers' attained age, 10 loci were associated (p<5*10-8), including 8 previously identified for traits including survival, Alzheimer's and cardiovascular disease. Of these, 4 were also associated with longest 10% survival (mothers age ≥90 years, fathers ≥87 years), with 2 additional associations including MC2R intronic variants (coding for the adrenocorticotropic hormone receptor). Mother's age at death was associated with 3 additional loci (2 linked to autoimmune conditions), and 8 for fathers only. An attained age genetic risk score associated with parental survival in the US Health and Retirement Study and the Wisconsin Longitudinal Study and with having a centenarian parent (n=1,181) in UK Biobank. The results suggest that human longevity is highly polygenic with prominent roles for loci likely involved in cellular senescence and inflammation, plus lipid metabolism and cardiovascular conditions. There may also be gender specific routes to longevity.

Personality Predicts Mortality Risk: An Integrative Data Analysis of 15 International Longitudinal Studies

This study examined the Big Five personality traits as predictors of mortality risk, and smoking as a mediator of that association. Replication was built into the fabric of our design: we used a Coordinated Analysis with 15 international datasets, representing 44,094 participants. We found that high neuroticism and low conscientiousness, extraversion, and agreeableness were consistent predictors of mortality across studies. Smoking had a small mediating effect for neuroticism. Country and baseline age explained variation in effects: studies with older baseline age showed a pattern of protective effects (HR<1.00) for openness, and U.S. studies showed a pattern of protective effects for extraversion. This study demonstrated coordinated analysis as a powerful approach to enhance replicability and reproducibility, especially for aging-related longitudinal research.

Myocardial infarction in the Wisconsin Longitudinal Study: the interaction among environmental, health, social, behavioural and genetic factors

OBJECTIVES

This study examined how environmental, health, social, behavioural and genetic factors interact to contribute to myocardial infarction (MI) risk.

DESIGN

Survey data collected by Wisconsin Longitudinal Study (WLS), USA, from 1957 to 2011, including 235 environmental, health, social and behavioural factors, and 77 single- nucleotide polymorphisms were analysed for association with MI. To identify associations with MI we utilized recursive partitioning and random forest prior to logistic regression and chi-squared analyses.

PARTICIPANTS

6198 WLS participants (2938 men; 3260 women) who (1) had a MI before 72 years and (2) had a MI between 65 and 72 years.

RESULTS

In men, stroke (LR OR: 5.01, 95% CI 3.36 to 7.48), high cholesterol (3.29, 2.59 to 4.18), diabetes (3.24, 2.53 to 4.15) and high blood pressure (2.39, 1.92 to 2.96) were significantly associated with MI up to 72 years of age. For those with high cholesterol, the interaction of smoking and lower alcohol consumption increased prevalence from 23% to 41%, with exposure to dangerous working conditions, a factor not previously linked with MI, further increasing prevalence to 50%. Conversely, MI was reported in <2.5% of men with normal cholesterol and no history of diabetes or depression. Only stroke (4.08, 2.17 to 7.65) and diabetes (2.71, 1.81 to 4.04) by 65 remained significantly associated with MI for men after age 65. For women, diabetes (5.62, 4.08 to 7.75), high blood pressure (3.21, 2.34 to 4.39), high cholesterol (2.03, 1.38 to 3.00) and dissatisfaction with their financial situation (4.00, 1.94 to 8.27) were significantly associated with MI up to 72 years of age. Conversely, often engaging in physical activity alone (0.53, 0.32 to 0.89) or with others (0.34, 0.21 to 0.57) was associated with the largest reduction in odds of MI. Being non-diabetic with normal blood pressure and engaging in physical activity often lowered prevalence of MI to 0.2%. Only diabetes by 65 (4.25, 2.50 to 7.24) and being exposed to dangerous work conditions at 54 (2.24, 1.36 to 3.69) remained significantly associated with MI for women after age 65, while still menstruating at 54 (0.46, 0.23 to 0.91) was associated with reduced odds of MI.

CONCLUSIONS

Together these results indicate important differences in factors associated with MI between the sexes, that combinations of factors greatly influence the likelihood of MI, that MI-associated factors change and associations weaken after 65 years of age in both sexes, and that the limited genotypes assessed were secondary to environmental, health, social and behavioral factors.

The Influence of Men's Military Service on Smoking Across the Life Course

The military is described as a social context that contributes to the (re-)initiation or intensification of cigarette smoking. We draw on data from the 1985-2014 National Survey of Drug Use and Health (NSDUH) and the Wisconsin Longitudinal Study (WLS) to conduct complementary sub-studies of the influence of military service on men's smoking outcomes across the life course. Descriptive findings from an age-period-cohort analysis of NSDUH data document higher probabilities of current smoking and heavy smoking among veteran men across a broad range of cohorts and at all observed ages. Findings from sibling fixed-effects Poisson models estimated on the WLS data document longer durations of smoking among men who served in the military and no evidence that selection explains the observed relationship. Together, these results provide novel and potentially generalizable evidence that participation in the military in early adulthood exerts a causal influence on smoking across the life course.

How Different Forms of Health Matter to Political Participation

Physical and mental health is known to have wide influence over most aspects of social life-be it schooling and employment or marriage and broader social engagement-but has received limited attention in explaining different forms of political participation. We analyze a unique dataset with a rich array of objective measures of cognitive and physical well-being and two objective measures of political participation, voting and contributing money to campaigns and parties. For voting, each aspect of health has a powerful effect on par with traditional predictors of participation such as education. In contrast, health has little to no effect on making campaign contributions. We recommend additional attention to the multifaceted affects of health on different forms of political participation.

Do Functional Health Inequalities Decrease in Old Age?

Although the relationship between educational attainment and health is well established, there is disagreement about how this relationship changes across the life course. Some studies have shown that educational health disparities widen in middle age and then start to abate in old age, whereas others have shown that health disparities continue to widen in old age. The author used the 1992-2002 Health and Retirement Study to shed new light on this old debate. Because findings of declining health inequalities in old age are often dismissed as a product of mortality selection and cohort effects, this study primarily aimed to address these claims. The author found that cohort effects and mortality selection do not fully explain shrinking educational disparities in functional health in old age. Further work is needed to explore explanations for diminishing health disparities health in old age.

The Implications of Unintended Pregnancies for Mental Health in Later Life

Despite decades of research on unintended pregnancies, we know little about the health implications for the women who experience them. Moreover, no study has examined the implications for women whose pregnancies occurred before Roe v. Wade was decided--nor whether the mental health consequences of these unintended pregnancies continue into later life. Using the Wisconsin Longitudinal Study, a 60-year ongoing survey, we examined associations between unwanted and mistimed pregnancies and mental health in later life, controlling for factors such as early life socioeconomic conditions, adolescent IQ, and personality. We found that in this cohort of mostly married and White women, who completed their pregnancies before the legalization of abortion, unwanted pregnancies were strongly associated with poorer mental health outcomes in later life.

Cohort profile: Wisconsin longitudinal study (WLS)

The Wisconsin Longitudinal Study (WLS) is a longitudinal study of men and women who graduated from Wisconsin high schools in 1957 and one of their randomly selected siblings. Wisconsin is located in the upper midwest of the United States and had a population of approximately 14 000 000 in 1957, making it the 14th most populous state at that time. Data spanning almost 60 years allow researchers to link family background, adolescent characteristics, educational experiences, employment experiences, income, wealth, family formation and social and religious engagement to midlife and late-life physical health, mental health, psychological well-being, cognition, end of life planning and mortality. The WLS is one of the few longitudinal data sets that include an administrative measure of cognition from childhood. Further, recently collected saliva samples allow researchers to explore the inter-relationships among genes, behaviours and environment, including genetic determinants of behaviours (e.g. educational attainment); the interactions between genes and environment; and how these interactions predict behaviours. Most panel members were born in 1939, and the sample is broadly representative of White, non-Hispanic American men and women who have completed at least a high school education. Siblings cover several adjoining cohorts: they were born primarily between 1930 and 1948. At each interview, about two-thirds of the sample lived in Wisconsin, and about one-third lived elsewhere in the United States or abroad. The data, along with documentation, are publicly accessible and can be accessed at http://www.ssc.wisc.edu/wlsresearch/. Requests for protected data or assistance should be sent to wls@ssc.wisc.edu.

Assessment of genetic and nongenetic interactions for the prediction of depressive symptomatology: an analysis of the Wisconsin Longitudinal Study using machine learning algorithms

OBJECTIVES

We examined depression within a multidimensional framework consisting of genetic, environmental, and sociobehavioral factors and, using machine learning algorithms, explored interactions among these factors that might better explain the etiology of depressive symptoms.

METHODS

We measured current depressive symptoms using the Center for Epidemiologic Studies Depression Scale (n = 6378 participants in the Wisconsin Longitudinal Study). Genetic factors were 78 single nucleotide polymorphisms (SNPs); environmental factors-13 stressful life events (SLEs), plus a composite proportion of SLEs index; and sociobehavioral factors-18 personality, intelligence, and other health or behavioral measures. We performed traditional SNP associations via logistic regression likelihood ratio testing and explored interactions with support vector machines and Bayesian networks.

RESULTS

After correction for multiple testing, we found no significant single genotypic associations with depressive symptoms. Machine learning algorithms showed no evidence of interactions. Naïve Bayes produced the best models in both subsets and included only environmental and sociobehavioral factors.

CONCLUSIONS

We found no single or interactive associations with genetic factors and depressive symptoms. Various environmental and sociobehavioral factors were more predictive of depressive symptoms, yet their impacts were independent of one another. A genome-wide analysis of genetic alterations using machine learning methodologies will provide a framework for identifying genetic-environmental-sociobehavioral interactions in depressive symptoms.

Benefits of educational attainment on adult fluid cognition: international evidence from three birth cohorts

BACKGROUND

Educational attainment is highly correlated with social inequalities in adult cognitive health; however, the nature of this correlation is in dispute. Recently, researchers have argued that educational inequalities are an artefact of selection by individual differences in prior cognitive ability, which both drives educational attainment and tracks across the rest of the life course. Although few would deny that educational attainment is at least partly determined by prior cognitive ability, a complementary, yet controversial, view is that education has a direct causal and lasting benefit on cognitive development.

METHODS

We use observational data from three birth cohorts, with cognition measured in adolescence and adulthood. Ordinary least squares regression was used to model the relationship between adolescent cognition and adult fluid cognition and to test the sensitivity of our analyses to sample selection, projection and backdoor biases using propensity score matching.

RESULTS

We find that having a university education is correlated with higher fluid cognition in adulthood, after adjustment for adolescent cognition. We do not find that adolescent cognition, gender or parental social class consistently modify this effect; however, women benefited more in the 1946 sample from Great Britain.

CONCLUSIONS

In all three birth cohorts, substantial educational benefit remained after adjustment for adolescent cognition and parental social class, offsetting an effect equivalent of 0.5 to 1.5 standard deviations lower adolescent cognition. We also find that the likelihood of earning a university degree depends in part on adolescent cognition, gender and parental social class. We conclude that inequalities in adult cognition derive in part from educational experiences after adolescence.

The social patterns of a biological risk factor for disease: race, gender, socioeconomic position, and C-reactive protein

OBJECTIVE

Understand the links between race and C-reactive protein (CRP), with special attention to gender differences and the role of class and behavioral risk factors as mediators.

METHOD

This study utilizes the National Social Life, Health, and Aging Project data, a nationally representative study of older Americans aged 57-85 to explore two research questions. First, what is the relative strength of socioeconomic versus behavioral risk factors in explaining race differences in CRP levels? Second, what role does gender play in understanding race differences? Does the relative role of socioeconomic and behavioral risk factors in explaining race differences vary when examining men and women separately?

RESULTS

When examining men and women separately, socioeconomic and behavioral risk factor mediators vary in their importance. Indeed, racial differences in CRP among men aged 57-74 are little changed after adjusting for both socioeconomic and behavioral risk factors with levels 35% higher for black men as compared to white men. For women aged 57-74, however, behavioral risk factors explain 30% of the relationship between race and CRP.

DISCUSSION

The limited explanatory power of socioeconomic position and, particularly, behavioral risk factors, in elucidating the relationship between race and CRP among men, signals the need for research to examine additional mediators, including more direct measures of stress and discrimination.

Education and health in late-life among high school graduates: Cognitive versus psychological aspects of human capital

Just as postsecondary schooling serves as a dividing line between the advantaged and disadvantaged on outcomes like income and marital status, it also serves as a dividing line between the healthy and unhealthy. Why are the better educated healthier? Human capital theory posits that education makes one healthier via cognitive (skill improvements) and noncognitive psychological resources (traits such as conscientiousness and a sense of mastery). I employ the Wisconsin Longitudinal Study (1957-2005) to test the relative strength of measures of cognitive human capital versus noncognitive psychological human capital in explaining the relationship between education and health outcomes among high school graduates. I find little evidence that noncognitive psychological human capital is a significant mediator, but find a relatively significant role for cognitive human capital, as measured by high school academic performance. It is not just higher educational attainment; academic performance is strongly linked to health in later life.

Upstream solutions: does the supplemental security income program reduce disability in the elderly?

CONTEXT

The robust relationship between socioeconomic factors and health suggests that social and economic policies might substantially affect health, while other evidence suggests that medical care, the main focus of current health policy, may not be the primary determinant of population health. Income support policies are one promising avenue to improve population health. This study examines whether the federal cash transfer program to poor elderly, the Supplemental Security Income (SSI) program, affects old-age disability.

METHODS

This study uses the 1990 and 2000 censuses, employing state and year fixed-effect models, to test whether within-state changes in maximum SSI benefits over time lead to changes in disability among people aged sixty-five and older.

FINDINGS

Higher benefits are linked to lower disability rates. Among all single elderly individuals, 30 percent have mobility limitations, and an increase of $100 per month in the maximum SSI benefit caused the rate of mobility limitations to fall by 0.46 percentage points. The findings were robust to sensitivity analyses. First, analyses limited to those most likely to receive SSI produced larger effects, but analyses limited to those least likely to receive SSI produced no measurable effect. Second, varying the disability measure did not meaningfully alter the findings. Third, excluding the institutionalized, immigrants, individuals living in states with exceptionally large benefit changes, and individuals living in states with no SSI supplements did not change the substantive conclusions. Fourth, Medicaid did not confound the effects. Finally, these results were robust for married individuals.

CONCLUSIONS

Income support policy may be a significant new lever for improving population health, especially that of lower-income persons. Even though the findings are robust, further analyses are needed to confirm their reliability. Future research should examine a variety of different income support policies, as well as whether a broader range of social and economic policies affect health.

Socioeconomic position and health: the differential effects of education versus income on the onset versus progression of health problems

This article seeks to elucidate the relationship between socioeconomic position and health by showing how different facets of socioeconomic position (education and income) affect different stages (onset vs. progression) of health problems. The biomedical literature has generally treated socioeconomic position as a unitary construct. Likewise, the social science literature has tended to treat health as a unitary construct. To advance our understanding of the relationship between socioeconomic position and health, and ultimately to foster appropriate policies and practices to improve population health, a more nuanced approach is required--one that differentiates theoretically and empirically among dimensions of both socioeconomic position and health. Using data from the Americans' Changing Lives Study (1986 through 2001/2002), we show that education is more predictive than income of the onset of both functional limitations and chronic conditions, while income is more strongly associated than education with the progression of both.