Doctor: Mikaela Bloomberg

Title: Socioeconomic determinants of sex differences in healthy ageing: a cross-national examination of cognition and functional limitation in older adults

Supervisors: Séverine Sabia, Archana Singh-Manoux

Doctoral school: University College London

Date of thesis defense: 09/2022

Funding: UK Economic and Social Research Council

Thesis abstract

Background: Sex inequalities in education may contribute to sex differences in cognitive and functional status in old age. This thesis examines the role of education in sex differences in cognitive and functional ageing across birth cohorts and in high- and middle-income countries.

Methods: The thesis includes three investigations, with analyses for each undertaken before and after adjustment for education and then stratified by education level. The thesis uses: 1) mixed effects linear models to examine sex differences in cognitive ageing in three birth cohorts (birth years 1930-1955; N = 15,924 UK-based participants); 2) weighted linear models to compare sex differences in cognitive function between the US and four middle-income countries (N = 70,846); and 3) mixed effects ordinal logistic models to examine sex differences in functional limitations in four birth cohorts (birth years 1895-1960; N = 62,375 participants from 11 countries).

Results: Before adjustment for education, women outperformed men in memory and orientation in high- but not middle-income countries. Men generally outperformed women in attention and fluency. Sex differences in cognitive function were less favourable to women in middle compared to high- income countries and in earlier-born birth cohorts. Women were more likely to have functional limitations than men. Adjustment for education attenuated or eliminated male advantages for both cognitive and functional outcomes, increased female advantages, and reduced differences in sex inequalities across birth cohorts. For cognitive function, adjustment for education attenuated differences in sex inequalities between middle- and high-income countries. Stratification by education revealed male advantages in cognitive function were present in less educated persons only.

Conclusion: Sex inequalities in education contribute to sex inequalities in cognitive function and to a lesser extent functional limitations in old age. Gender equity in access to education is an important target to reduce sex disparities in cognitive and functional ageing.

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