Fertility Characteristics and Cognitive Function Trajectories: Panel Data Analysis of Two Longitudinal Cohort Studies

Objective To explore the effects of fertility experience and child gender composition on the cognitive function trajectories of older adults, and to compare the cross-cultural differences between Chinese and European elderly populations. Methods This study integrated multi-wave longitudinal data from the China Health and Retirement Longitudinal Study (CHARLS) and the Survey of Health, Ageing and Retirement in Europe (SHARE). A total of 15,257 adults aged 60 years and above were included as research subjects. Group-Based Trajectory Models (GBTM) were used to construct cognitive function trajectories, and multinomial logistic regression models were applied to empirically analyze the effects of fertility experience and child gender structure on cognitive trajectories, as well as to compare the differences between Chinese and European groups. Results The cognitive function of older adults could be divided into three stable trajectories: low, medium, and high levels. Fertility experience showed a non-linear association with cognitive function trajectories. Having 1–2 children exhibited a cognitive protective effect, while increased fertility experience elevated the risk of cognitive decline. After controlling for fertility experience, significant cross-cultural differences were observed in the effect of child gender: in the Chinese sample, having only sons had a significant protective effect on the cognitive function of older adults and effectively reduced the risk of cognitive decline, while no statistically significant difference was found in the group with only daughters. In the European sample, there was no statistically significant association between child gender and cognitive trajectories. Conclusion Fertility characteristics significantly affect the changing patterns of cognitive function in older adults, and there is obvious China-Europe heterogeneity in the effect of child gender, which mainly stems from differences in family culture, gender concepts, and social welfare systems. This study can provide empirical evidence for the development of elderly cognitive health interventions and healthy aging policies in different cultural contexts.