Physical activity and its fluctuations in relation to depressive symptoms: A national longitudinal study among Chinese adults

Physical activity (PA) may prevent depressive symptoms, however, PA fluctuations may have different effects. Using three waves of nationally representative data, this study aimed to examine the effects of PA fluctuations on depressive symptoms. Participants comprised 7633 adults free of depressive symptoms at the first two waves (Mage = 45.26, 54.70 % males). They completed the China Family Panel Study in 2016 (T1), 2018 (T2), and 2020 (T3), respectively. Depressive symptoms were measured by the Center for Epidemiologic Studies Depression (CES–D) scale using a cutoff of 16. Participants' PA levels were split into regular PA or infrequent PA groups. Changes in PA levels between T1 and T2 were classified into four groups: maintained infrequent PA, initiated regular PA, ceased regular PA, and persisted regular PA. The incidence of depressive symptoms was 20.22 % (19.05 % possible and 1.17 % severe depression). After multivariate adjustment, Poisson regression showed that persistent regular PA had 17.8 % (95 % CI: 0.724, 0.934) lower risks of incident depressive symptoms compared to maintained infrequent PA. And adults who ceased regular PA were more likely to experience depressive symptoms than those who persisted in regular PA (RR = 1.188, 95 % CI: 1.010, 1.398). All items were self-reported. CES–D only examined self-diagnosed depressive symptoms, not medical diagnoses. Adults who persisted in regular PA may have a lower possibility of developing depressive symptoms. The finding might serve as an empirical reference to depression prevention.