Disaggregating between- and within-person associations of mastery and cognitive function: age as a moderator.

Background: Mastery may shape the way individuals cope with life challenges and influence cognitive function in later life. Mastery grows out of traumatic experience and could change over the life course. This study examined the within-person and between-person associations of mastery and cognitive function, and if these associations were moderated by age in the United States.

Method: Data were derived from three time points (2006-2008, 2010-2012, and 2014-2016) of the Health and Retirement Study, with 14,461 adults (aged 51 or above). Cognitive function was measured through a 27-point Telephone Interview Cognitive Screen (TICS). Mastery was measured by a modified Pearlin Mastery Scale. Multilevel modeling was employed to analyze the data.

Results: Both within-person ( $\beta$ =0.124, SE = 0.023, p < 0.001) and between-person ( $\beta$ =0.089, SE = 0.029, p = 0.002) mastery were significantly associated with cognitive function. Older adults with higher between-person mastery tended to have slower cognitive decline ( $\beta$ =0.063, SE = 0.021, p < 0.001). Moreover, age moderated the within-person ( $\beta$ =0.013, SE = 0.003, p < 0.001) associations between mastery and cognition with a stronger association observed among individuals with older age.

Conclusions: The current study provides evidence for within-person and between-person associations between mastery and global cognition in the United States as well as the moderating role of age. The design of the current study did not directly assess the causal direction between mastery and cognitive function. Future studies could test the directionality of associations between mastery and cognitive function.