Sex as a Moderator of the Association between Cardiorespiratory Fitness and Depressive Symptoms in Older Adults

Objectives The study investigates sex differences in how cardiorespiratory fitness (CRF) and accelerometry-based physical activity relate to depressive symptoms in community-dwelling older adults. We hypothesized that the relationship between higher CRF and PA levels with lower depressive symptoms would be more prominent in women relative to men. Methods Participants included 648 community-dwelling adults aged 65-80 (71% women (n = 461); mean age [SD] = 69.88 [3.75]) without evidence of clinical depression (Geriatric Depression Scale score <9). CRF was assessed using a graded exercise test, and PA (light PA, moderate-to-vigorous PA [MVPA]) was assessed using a 7-day actigraphy protocol. Subsyndromal depressive symptoms were evaluated using the Hospital Anxiety and Depression Scale. Multiple linear regression analyses were performed to examine the relationships between CRF, light PA, MVPA, and depressive symptoms, adjusting for age, sex, years of education, body mass index, and anxiety symptoms, and to evaluate the moderating role of sex. Results Higher CRF and greater amounts of MVPA and light PA were associated with fewer depressive symptoms (β=-0.12, p = 0.010; β=-0.09, p = 0.021; and β=-0.13, p < 0.001, respectively) within the overall sample. However, moderation analysis by sex revealed that higher CRF was associated with fewer depressive symptoms only among female participants (β=-0.19, p < 0.001). Sex moderation effects were not observed for light PA or MVPA. Discussion These findings suggest CRF is a key physiological correlate of subsyndromal depressive symptoms in late life, particularly for women. Understanding sex-specific responses to PA may inform tailored prevention and intervention strategies targeting mood symptoms prior to full clinical expression of depression. Clinical Trial Registration NCT02875301