Family Size Across the Life Course and Cognitive Decline in Older Mexican Adults

A growing body of research has identified associations between family size and cognition in older adults. These studies largely focus on older adults' own fertility history instead of sibship size, defined as one's number of siblings. Sibship size may affect cognitive development during early childhood, creating differences that may persist into late life. Using a gendered life course framework, this study evaluates how family size across the life course (both sibship size and number of children) relates to cognitive aging among older Mexican adults.

Data come from the 2012, 2015, 2018, and 2021 waves of the Mexican Health and Aging Study (n = 14,872 adults age 50+). We use latent growth curve models to evaluate how family size (sibship size and fertility history) relates with levels of latent general cognitive ability and 9-year cognitive decline and variation across gender.

Small sibship size related to higher levels of cognitive ability among men, but not women. This benefit was somewhat reduced when educational attainment was accounted for. Regarding fertility history, we observed an inverse U-shaped relationship with the level of cognitive ability, regardless of gender, that remained significant even after accounting for sibship size and other confounders. Neither family size measure predicted the rate of cognitive decline.

This research broadens our understanding of family size and cognition associations in the context of Mexico's changing demographics that challenge the reliance on family support in late life and highlights potential gender differences.