Longitudinal associations between specific types/amounts social contact and cognitive function among middle-aged and elderly Chinese: A causal inference and longitudinal targeted maximum likelihood estimation analysis.

BACKGROUND: Social contact has demonstrated associations with cognitive function, while the literature on the effect of specific social relationship subdomains on cognitive function is limited. This study aimed to examine the causal effects of specific types/amounts of social contact on cognitive function among middle-aged and elderly Chinese. METHODS: A total of 38,883 middle-aged and elderly adults from the China Health and Retirement Longitudinal Study were involved. Social contact in this study included interaction with families, taking care of grandchildren, interaction with friends, and participation in three types of social activities. We performed the linear mixed-effects model analysis with propensity score approach and the longitudinal targeted maximum likelihood-based estimation analysis after adjusting for potential covariates and confounders. RESULTS: Interaction with families, caring for grandchildren, interaction with friends and participation in social activities were all associated with cognitive z-scores. Participants who interacted with families "2-3 times a week" and "once a week" versus "almost every day" had higher cognitive z-scores. Those who interacted with friends and participated in social activities "almost every week" versus "almost daily" had higher cognitive z-scores. LIMITATIONS: The assessment of cognition was biased against people with poor education due to elements of language and mathematical testing, and against those with visual impairment. CONCLUSIONS: Social contact was associated with better cognitive function among middle-aged and elderly Chinese. Social contact "1-3 times a week" was optimal for cognitive function. More social contact in middle-aged and elderly Chinese led to less cognitive decline in later life than in their inactive peers.