Measuring Sex and Gender in Aging and Alzheimer's Research: Results of a National Survey

Hormonal contraception and risk for cognitive impairment or Alzheimer's disease and related dementias in young women: a scoping review of the evidence

Introduction

Women are significantly more likely to develop Alzheimer's disease and related dementias (ADRD) than men. Suggestions to explain the sex differences in dementia incidence have included the influence of sex hormones with little attention paid to date as to the effect of hormonal contraception on brain health. The aim of this scoping review is to evaluate the current evidence base for associations between hormonal contraceptive use by women and non-binary people in early adulthood and brain health outcomes.

Methods

A literature search was conducted using EMBASE, Medline and Google Scholar, using the keywords "hormonal contraception" OR "contraception" OR "contraceptive" AND "Alzheimer*" OR "Brain Health" OR "Dementia".

Results

Eleven papers were identified for inclusion in the narrative synthesis. Studies recruited participants from the UK, USA, China, South Korea and Indonesia. Studies included data from women who were post-menopausal with retrospective data collection, with only one study contemporaneously collecting data from participants during the period of hormonal contraceptive use. Studies reported associations between hormonal contraceptive use and a lower risk of ADRD, particularly Alzheimer's disease (AD), better cognition and larger grey matter volume. Some studies reported stronger associations with longer duration of hormonal contraceptive use, however, results were inconsistent. Four studies reported no significant associations between hormonal contraceptive use and measures of brain health, including brain age on MRI scans and risk of AD diagnosis.

Discussion

Further research is needed on young adults taking hormonal contraceptives, on different types of hormonal contraceptives (other than oral) and to explore intersections between sex, gender, race and ethnicity.

Systematic Review Registration

https://doi.org/10.17605/OSF.IO/MVX63, identifier: OSF.io: 10.17605/OSF.IO/MVX63.

Gender of Study Partners and Research Participants Associated With Differences in Study Partner Ratings of Cognition and Activity Level

OBJECTIVES

Studies of Alzheimer's disease typically include "study partners" (SPs) who report on participants' cognition and function. Prior studies show SP reports differ depending on the relationship between the SP and participant, that is, spouse or adult child. Adult children SPs are typically female. Could differing reports be due to gender? Knowing this may help explain variability in measurement.

METHODS

The Aging, Demographics, and Memory Study enrolled a subset of participants from the Health and Retirement Study. Each participant had an SP. Bivariate and multivariable regression models compared 718 SP-participant dyads.

RESULTS

In analyses of 4 groups defined by SP and participant gender, dyads composed of 2 women were less likely to identify as White (75.8%, 95% confidence interval [CI], 70.4-80.5) than dyads composed of 2 men (93.3%, 95% CI, 81.2-97.8). In analyses adjusted for the severity of cognitive and functional impairment, women SPs rated women participants as more active than they rated men, mean 2.15 (95% CI, 2.07-2.22) versus mean 2.30 (95% CI, 2.24-2.37), respectively, on a 4-point scale. Similarly, men SPs rated women participants as more active than they rated men, mean 2.1 (95% CI, 2.0-2.2) and mean 2.4 (95% CI, 2.3-2.5), respectively. In an analysis of cognitively unimpaired participants, women SPs rated participants' memory worse than men SPs did (p < .05).

DISCUSSION

SP and participant gender influence SPs' reports of another person's cognition and activity level. Our findings expand what is understood about how nondisease factors influence measures of disease severity.

The structural and social determinants of Alzheimer's disease related dementias

INTRODUCTION

The projected growth of Alzheimer's disease (AD) and AD-related dementia (ADRD) cases by midcentury has expanded the research field and impelled new lines of inquiry into structural and social determinants of health (S/SDOH) as fundamental drivers of disparities in AD/ADRD.

METHODS

In this review, we employ Bronfenbrenner's ecological systems theory as a framework to posit how S/SDOH impact AD/ADRD risk and outcomes.

RESULTS

Bronfenbrenner defined the "macrosystem" as the realm of power (structural) systems that drive S/SDOH and that are the root cause of health disparities. These root causes have been discussed little to date in relation to AD/ADRD, and thus, macrosystem influences, such as racism, classism, sexism, and homophobia, are the emphasis in this paper.

DISCUSSION

Under Bronfenbrenner's macrosystem framework, we highlight key quantitative and qualitative studies linking S/SDOH with AD/ADRD, identify scientific gaps in the literature, and propose guidance for future research.

HIGHLIGHTS

Ecological systems theory links structural/social determinants to AD/ADRD. Structural/social determinants accrue and interact over the life course to impact AD/ADRD. Macrosystem is made up of societal norms, beliefs, values, and practices (e.g., laws). Most macro-level determinants have been understudied in the AD/ADRD literature.

Fine temporal brain network structure modularizes and localizes differently in men and women: insights from a novel explainability framework

Deep learning has become an effective tool for classifying biological sex based on functional magnetic resonance imaging (fMRI). However, research on what features within the brain are most relevant to this classification is still lacking. Model interpretability has become a powerful way to understand "black box" deep-learning models, and select features within the input data that are most relevant to the correct classification. However, very little work has been done employing these methods to understand the relationship between the temporal dimension of functional imaging signals and the classification of biological sex. Consequently, less attention has been paid to rectifying problems and limitations associated with feature explanation models, e.g. underspecification and instability. In this work, we first provide a methodology to limit the impact of underspecification on the stability of the measured feature importance. Then, using intrinsic connectivity networks from fMRI data, we provide a deep exploration of sex differences among functional brain networks. We report numerous conclusions, including activity differences in the visual and cognitive domains and major connectivity differences.

Cognitive Aging with Dementia, Mild Cognitive Impairment, or No Impairment: A Comparison of Same- and Mixed-Sex Couples

BACKGROUND

Lesbian and gay older adults have health disparities that are risk factors for Alzheimer's disease, yet little is known about the neurocognitive aging of sexual minority groups.

OBJECTIVE

To explore cross-sectional and longitudinal dementia outcomes for adults in same-sex relationships (SSR) and those in mixed-sex relationships (MSR).

METHODS

This prospective observational study utilized data from the National Alzheimer's Coordinating Center Uniform Data Set (NACC UDS) collected from contributing Alzheimer's Disease Research Centers. Participants were adults aged 55+ years at baseline with at least two visits in NACC UDS (from September 2005 to March 2021) who had a spouse, partner, or companion as a co-participant. Outcome measures included CDR® Dementia Staging Instrument, NACC UDS neuropsychological testing, and the Functional Activities Questionnaire. Multivariable linear mixed-effects models accounted for center clustering and repeated measures by individual.

RESULTS

Both MSR and SSR groups experienced cognitive decline regardless of baseline diagnosis. In general, MSR and SSR groups did not differ statistically on cross-sectional or longitudinal estimates of functioning, dementia severity, or neuropsychological testing, with two primary exceptions. People in SSR with mild cognitive impairment showed less functional impairment at baseline (FAQ M = 2.61, SD = 3.18 vs. M = 3.97, SD = 4.53, respectively; p < 0.01). The SSR group with dementia had less steep decline in attention/working memory (β estimates = -0.10 versus -0.18; p < 0.01).

CONCLUSION

Participants in SSR did not show cognitive health disparities consistent with a minority stress model. Additional research into protective factors is warranted.

A systematic review of measures of gender and biological sex: Exploring candidates for Alzheimer's disease and related dementias (AD/ADRD) research

Background

Gender and biological sex are social and structural determinants of health and umbrella concepts encompassing many distinct attributes. This systematic review summarizes measures of gender and biological sex published in the biomedical literature. The goal was to identify measures that may be useful to researchers studying Alzheimer's disease and Alzheimer's disease related dementias (AD/ADRD).

Methods

A search of PubMed, Embase, and PsycINFO (ProQuest platform) databases from 2000 to 2021 identified 1454 articles, which were then screened by five independent reviewers. Measures of gender and biological sex are summarized according to theoretical commitments and psychometric properties.

Results

Twenty-nine measures were identified that assessed gender-related constructs, and 4 were identified that assessed biological factors. Self-report instruments characterized aspects of gender, such as gender stereotypes, norms, and ideologies. One measure was developed with a focus on older adults (65+ years).

Discussion

We offer recommendations to guide measurement of gender in AD/ADRD research, including how the use of specific existing measures may help advance AD/ADRD research. The lack of gender measures for older adults limits AD/ADRD research. New measures may be needed to address lifespan and generational differences in gender factors.

Highlights

A review of articles identifies 29 measures of gender in biomedical research.Gender is captured using multidimensional, self-reported concepts.One measure was developed with a focus on older adults (65+).

Expanding the scope of health disparities research in Alzheimer's disease and related dementias: Recommendations from the "Leveraging Existing Data and Analytic Methods for Health Disparities Research Related to Aging and Alzheimer's Disease and Related Dementias" Workshop Series

Topics discussed at the "Leveraging Existing Data and Analytic Methods for Health Disparities Research Related to Aging and Alzheimer's Disease and Related Dementias" workshop, held by Duke University and the Alzheimer's Association with support from the National Institute on Aging, are summarized.  Ways in which existing data resources paired with innovative applications of both novel and well-known methodologies can be used to identify the effects of multi-level societal, community, and individual determinants of race/ethnicity, sex, and geography-related health disparities in Alzheimer's disease and related dementia are proposed.  Current literature on the population analyses of these health disparities is summarized with a focus on identifying existing gaps in knowledge, and ways to mitigate these gaps using data/method combinations are discussed at the workshop.  Substantive and methodological directions of future research capable of advancing health disparities research related to aging are formulated.

Consideration of sex and gender in Alzheimer's disease and related disorders from a global perspective

Sex or gender differences in the risk of Alzheimer's disease and related dementias (ADRD) differ by world region, suggesting that there are potentially modifiable risk factors for intervention. However, few epidemiological or clinical ADRD studies examine sex differences; even fewer evaluate gender in the context of ADRD risk. The goals of this perspective are to: (1) provide definitions of gender, biologic sex, and sexual orientation. and the limitations of examining these as binary variables; (2) provide an overview of what is known with regard to sex and gender differences in the risk, prevention, and diagnosis of ADRD; and (3) discuss these sex and gender differences from a global, worldwide perspective. Identifying drivers of sex and gender differences in ADRD throughout the world is a first step in developing interventions unique to each geographical and sociocultural area to reduce these inequities and to ultimately reduce global ADRD risk. HIGHLIGHTS: The burden of dementia is unevenly distributed geographically and by sex and gender. Scientific advances in genetics and biomarkers challenge beliefs that sex is binary. Discrimination against women and sex and gender minority (SGM) populations contributes to cognitive decline. Sociocultural factors lead to gender inequities in Alzheimer's disease and related dementias (ADRD) worldwide.

Research Centers Collaborative Network Workshop on Sex and Gender Differences in Aging

Aging affects men and women differently; however, the impact of sex and gender on the aging process is not well understood. Moreover, these 2 concepts are often conflated, which further contributes to a lack of clarity on this important issue. In an effort to better understand the relevance of sex and gender in aging research, the Research Centers Collaborative Network sponsored a 1.5-day conference on sex and gender differences in aging that brought together key thought leaders from the 6 National Institute on Aging center programs. The meeting included sessions on comparing males and females, pathophysiological differences, sex/gender in clinical care, and gender and health in the social context. Presenters from a wide array of disciplines identified opportunities for multidisciplinary research to address current gaps in the field and highlighted the need for a more systematic approach to understanding the how and why of sex/gender differences, as well as the health implications of these differences and the sex/gender biases that affect clinical treatment and outcomes. This article summarizes the proceedings of the workshop and provides several recommendations to move the field forward, such as better data collection tools to assess the intersection of sex and gender in epidemiological research; a life course perspective with attention to fetal/developmental origins and key life stages; innovative animal models to distinguish contributions from sex hormones versus sex chromosomes; and integration of sex/gender into teaching and clinical practice. Ultimately, successful implementation of these recommendations will require thoughtful investigations across the translational spectrum and increased collaborations among those with expertise in sex and gender differences.

Establishing a Framework for Gathering Structural and Social Determinants of Health in Alzheimer's Disease Research Centers

Structural and social determinants of health (SSDoH) are environmental conditions in which individuals are born, live, learn, work, play, worship, and age that affect health, functioning, and quality-of-life outcomes across the life course. Growing evidence suggests that SSDoH can help to explain heterogeneity in outcomes in Alzheimer's disease and Alzheimer's disease and related dementias (AD/ADRD) research and clinical practice. The National Institute on Aging has prioritized collecting SSDoH data to elucidate disease mechanisms and aid discovery of disease-modifying treatments. However, a major nexus of AD/ADRD research, the national network of Alzheimer's Disease Research Centers (ADRCs), collects few SSDoH data. We describe a framework for feasibly gathering and modeling SSDoH data across ADRCs. We lay out key constructs, their measures, and empirical evidence for their importance in elucidating disease and prevention mechanisms. Toward a goal of translation, the framework proposes a modular structure with a core set of measures and options for adjunctive modules. We describe considerations for measuring SSDoH in existing geographically and culturally diverse research cohorts. We also outline a rationale for universal implementation of a set of SSDoH measures and juxtapose the approach with alternatives aimed at collecting SSDoH data.