Association of longitudinal changes in physical activity with allostatic load in midlife

It is known that physical activity (PA) helps improve physical and mental health; however, the association between longitudinal changes in PA and cumulative stress at midlife remains ill-defined. This study examined the association between leisure-time physical activity (LTPA) and chronic stress, quantified as allostatic load at midlife, in a population-based sample of Finnish adults.

We included members of the Northern Finland Birth Cohort 1966 (NFBC1966) who participated in follow-ups conducted at 31 and 46 years of age (n = 3358). Self-reported leisure-time moderate to vigorous physical activity (MVPA) levels were used to classify participants into two dichotomous groups based on World Health Organization recommendations for PA. According to changes in LTPA from 31 years to 46 years of age, participants were categorized into stable inactive, increased, decreased, and stable active groups. To ensure statistical robustness and enable comparison, two separate allostatic load indices (a 13-item index and a 5-item index) were used, based on biological markers collected in clinical examinations conducted at the 46-years-of-age follow-up. Poisson regression was used to analyze the strength of associations.

From early adulthood to midlife, participants with stable inactivity (rate ratio, RR = 1.18, 95 % confidence interval, CI: 1.11-1.25) or decreasing LTPA (RR = 1.10, 95 % CI: 1.02-1.19) were at a higher risk of allostatic load with the 13-item index compared to those with stable active PA. With the 5-item allostatic load index, only stable inactivity was significantly associated with allostatic load (RR=1.17, 95 % CI: 1.07-1.28). Increased LTPA did not significantly differ from stable activity in terms of risk of allostatic load with the 13-item index (RR = 1.01, 95 % CI: 0.94-1.09) or the 5-item index (RR=1.04, 95 % CI: 0.93-1.15).

Both lower-than-recommended and decreasing LTPA levels through adulthood are associated with the accumulation of chronic stress when transitioning from early adulthood to midlife.