Evaluating sex and gender as separate and interactive predictors of memory aging trajectory classes: an integrative data-driven approach

Abstract

Background: A priority in aging and dementia research is to integrate sex (biological attribute) and gender (sociocultural/behavioural characteristics) in theories, designs, analyses, and intervention protocols. We recently reported a data-mining procedure for operationalizing empirically-derived composite gender variables in archival databases. The present study extends the prior cross-sectional approach by examining sex and gender as separate and interactive predictors of longitudinal data-driven memory trajectory classes.

Methods: Participants (N = 746) contributed baseline data for binary sex (female/male), education (years), and empirically-derived composite variables representing complementary gender facets. These facets included Manual Tasks and Physical Activities; Social and Household Management; Leisure, Socializing, and Travel; Cognitive Activity and Brain Games; Health Perceptions and Practices; and Subjective Memory Beliefs. We integrated these into a longitudinal episodic memory trajectory distribution spanning 42 years (53-95) of aging. Data-driven latent class growth analysis (LCGA) on the trajectory distribution identified discriminable classes. Using the R3STEP approach, we separately tested sex, gender facets, and education as predictors of membership in the higher (healthier) trajectory classes relative to the lowest (benchmark) class. We then included interaction terms to test for sex moderation of gender effects. Finally, we identified all genotyped participants and tested whether sex and gender effects were moderated by Apolipoprotein E (APOE).

Results: LCGA revealed three memory classes: High-Stable (highest level/relatively stable), Moderate/Normal-Declining (average level/moderate decline), and Low-Declining (lowest level/steepest decline). Several variables separately predicted High-Stable membership. For sex, females were more likely than males to belong to this class. For gender, (a) higher scores for Social and Household Management, Cognitive Activity and Brain Games, and Subjective Memory Beliefs predicted High-Stable membership; and (b) higher scores for Manual Tasks and Physical Activities and Health Perceptions and Practices decreased the likelihood of High-Stable membership (relative to Low-Declining). Moderate/Normal-Declining membership was predicted by Social and Household Management (higher). For education, more years predicted High-Stable membership. Moderation analyses indicated that gender effects were consistent across both sexes and APOE carrier status.

Conclusions: Data-driven analyses show that biological sex and measurable facets of gender differentially contribute to memory trajectory patterns over a 42-year span of cognitively unimpaired aging.

Plain Language Summary

The question we studied: We learn much about aging and dementia by assessing how the same persons change over multiple time points in life. We were especially interested in changes in memory abilities, as these are related to both healthy aging and dementia. In this study we compared how memory abilities of women and men change over many years of aging and what conditions and experiences contribute to similar or different patterns.

How we studied it: We studied a group of over 700 adults between the ages of 53 and 92. We explored how long-term changes in memory abilities were related to several personal characteristics, such as sex, gender, lifetime education and genetic risk for Alzheimer’s disease.

What we found: Our first finding was that there was a group that included both female and male adults who showed patterns of memory aging that remained high and stable into their 80s and 90s. Our second finding was that being a member of this higher group was more likely for aging females than males. Our third finding was that gender characteristics, education, and genetic risk also played roles in predicting who was a member of this higher memory aging group.

Why it matters: Our results help us to better understand how some conditions and experiences of aging women and men can lead to sustained patterns of healthier changes in memory abilities. More precise knowledge about how women and men differ in these patterns and their predictors is an important step in finding ways to promote healthier aging for both women and men.