Associations of midlife fitness and obesity profiles with cognitive function

Low fitness and obesity at midlife are individually associated with later-life decline in cognition and health. However, the relationship between profiles of midlife fitness and obesity with midlife cognition is unclear and was examined by this study. Participants from the third follow-up of the Childhood Determinants of Adult Health study (2014-2019; aged 36-49 years) were assessed for obesity (body mass index [BMI]), cardiorespiratory (physical work capacity) and muscular fitness (isometric grip and leg strength), and these factors were entered into a latent profile analysis. Psychomotor-attention, learning-working memory and global cognition composites were derived from z-scores of individual CogState battery tests. Linear regression analyses examined associations between profiles of fitness and obesity with cognition, adjusting for age, sex, education, alcohol and smoking. Using data from 617 participants [44.4 +/- 2.6 (mean +/- SD) years, 52% female], we identified 5 mutually exclusive profiles of obesity and fitness. Relative to those with the lowest fitness and highest BMI (5% of sample), those with a profile of (1) highest muscular fitness and average BMI (9%), (2) average muscular fitness and BMI (61%) and (3) highest cardiorespiratory fitness (CRF) and below average BMI (7%) all exhibited better global cognition [at least 0.44 (0.12, 0.77) SD, 95% CI] and psychomotor-attention performance [at least 0.59 (0.27, 0.91) SD, 95% CI]. Compared with low fitness and unhealthy BMI levels, possessing average or high muscular and CRF and a healthy BMI in midlife was associated with better cognitive performance. Enhancing fitness and reducing obesity in midlife could contribute to improved cognitive performance in middle age. Profiles containing adults with a combination of low levels of cardiorespiratory and muscular fitness and higher levels of obesity were associated with lower psychomotor-attention and global cognition at midlife. Possessing average or higher levels of fitness, and lower obesity at midlife, was associated with better cognitive performance at midlife compared to those with lower fitness and unhealthy BMIs. Maintaining fitness and reducing obesity at midlife may contribute to greater cognitive performance at midlife and beyond and reduce the risk of cognitive decline.