Societal gender equality and spousal cognitive interdependence: A random-intercept cross-lagged analysis across 20...

Spouses often show concordant cognitive trajectories, but whether this reflects a within-dyad prospective association or merely shared environments and assortative mating remains unresolved, and whether it varies across cultural contexts is unknown.

We harmonised longitudinal data from 69,703 couples aged 50 years and older, contributing 91,115 couple-wave transitions across 20 countries, from four ageing cohorts (CHARLS, HRS, SHARE and MHAS); a fifth cohort, KLoSA, had cognitive data in a single wave and contributed to the cross-sectional analyses only. Random-Intercept Cross-Lagged Panel Models separated within-dyad prospective associations from stable between-dyad confounding; country-specific partner effects were pooled and examined by meta-regression against the UN Gender Inequality Index (GII) and Hofstede's Individualism Index.

Traditional cross-lagged models overestimated partner effects by 65-68%. After removing stable between-dyad variance, bidirectional within-dyad prospective associations persisted (β = 0.033 in both directions, P < 0.001). In an exploratory ecological meta-regression, the husband-to-wife association was inversely related to national gender inequality (GII b =  - 0.222, Knapp-Hartung P = 0.022), being larger in more egalitarian countries. This association was significant in 18 of 20 leave-one-country-out iterations but was attenuated to non-significance after adjustment for GDP per capita (b =  - 0.205, Knapp-Hartung P = 0.153).

Spousal cognitive concordance is not fully explained by stable between-dyad confounding such as assortative mating, although the within-dyad associations that remain are small. Their magnitude varied across countries in a pattern associated at the ecological level with societal gender equality, an exploratory finding that requires replication.