Identifying the relative contributions of body size across life course to midlife and late-life cognitive function: a Bayesian analysis from the Guangzhou Biobank Cohort Study

Objectives The relative contributions of life-course obesity to midlife and late-life cognitive function have not been reported. We examined the association of life-course body size with cognitive function and identified the relative contribution of body size at each life stage.

Design This was a study based on data from the Guangzhou Biobank Cohort Study.

Setting A community-based population in China.

Participants 9,303 participants without a history of dementia or other serious mental disorders were included, with a mean age of 59.9 years (standard deviation = 6.0 years).

Measurements Perceived childhood, adolescence, early adulthood, midlife, and current body size were assessed by Stunkard’s Figure Rating Scale (labelled 1–9, from very thin to very fat), and analysed as categorical or continuous variables. Cognitive function was assessed using the Mini-Mental State Examination (MMSE), and analysed as a continuous score. A Bayesian relevant life course exposure model was used to quantify the relative contributions of body size to cognitive function.

Results After adjustment for confounders, each one-figure increase in body size was associated with lower MMSE scores. The βs (95% confidence intervals) were −1.121 (−1.200, −1.043), −1.077 (−1.161, −0.993), −0.795 (−0.871, −0.719), −0.450 (−0.520, −0.380), −0.253 (−0.318, −0.188) for childhood, adolescence, early adulthood, midlife and current status, respectively. The contributions of larger body size to poorer cognitive function varied across life stages, with childhood and adolescence accounting for 58.96% (95% credible interval (CrI) = 49.81%–68.07%) and 38.52% (95% CrI = 29.11%–47.82%) of the association, respectively.

Conclusion Body size in childhood and adolescence mainly explained the negative association between life-course body size and cognitive function in midlife and late-life. This finding highlights the importance of early-life obesity prevention for maintaining cognitive function.