Mind-body Qigong Baduanjin exercises benefit cognition in community-dwelling older adults, yet mechanisms are poorly understood. We aimed to examine the moderation and mediation roles of sleep on intervention effects in cognition.

This 10-week trial included 78 (intervention: n = 47, control: n = 31) older Chinese adults at a daycare center. We measured the sleep quality, both subjective and objective cognition pre- and post-intervention. The intervention served as the independent variable and the post-pre changes in cognition were used as outcomes. Baseline sleep quality was examined as a moderator, while post-pre changes in sleep quality were considered as a mediator. We tested the interaction between intervention and the moderator using a linear regression model, with relevant covariates adjusted. Subgroup analyses were conducted for any potential interaction (p < 0.20). Mediation effects were analyzed through first modeling the effect of the independent variable on the mediator, and then modeling the effect of independent variable and the mediator on the outcome.

Compared to control, Qigong intervention significantly predicted improvements in subjective and objective cognition among older adults, particularly for poor sleepers but not good sleepers. Sleep improvements significantly mediated intervention effects on subjective cognition in participants with less daily exercise (indirect effect: β = -0.412, 95 % CI: [-0.910, -0.066]).

Qigong improved cognition in older Chinese, particularly those with sleep problems prior to the intervention. Sleep quality changes played a mediating role, especially in individuals with less exercise. Results shed light on future interventions in identifying targeted mediating/moderating factors of Qigong.