The impact of 24-h activity patterns on executive function in older adults with chronic diseases: analysis of the isotonic substitution effect

Objective 24-h activity encompasses four categories: light-intensity physical activity (LPA), moderate-to-vigorous-intensity physical activity (MVPA), sedentary behavior (SB), and sleep (SP). This study aims to investigate the effects of different physical activity components on executive function in older adults with chronic diseases and to examine substitution effects among activity components. The findings provide scientific evidence to inform physical activity interventions for improving executive function in older adults with chronic diseases. Methods A total of 105 older adults (72.64 ± 6.82 years) were recruited. Following questionnaire screening, 75 older adults with chronic diseases were ultimately included. Accelerometers objectively measured participants’ daily SP, SB, LPA, and MVPA. Executive function was objectively assessed using the Stroop task, N-back task, and More-odd-shifting task. Component linear regression equation assessed the relationship between different activities and executive function in older adults with chronic diseases. The dose–response effects of “one-for-one” substitutions between different activity behaviors were explored. Results Component linear regression results showed that SB positively correlated with inhibitory control ( β = 0.892, 95% CI = 0.044 to 1.741) and working memory ( β = 1.610, 95% CI = 0.801 to 2.420). MVPA was negatively correlated with inhibitory control ( β = −0.596, 95% CI = −1.156 to −0.036), while LPA was negatively correlated with working memory ( β = −0.969, 95% CI = −1.812 to −0.127). No significant association with cognitive flexibility was found ( p > 0.05). Isotemporal substitution results showed that for inhibitory control, replacing SB with SP for 30 min reduced z-scores by 0.068; replacing SB with MVPA for 30 min reduced z-scores by 0.285. For working memory, replacing SB with LPA every 30 min resulted in a z-score decrease of 0.152. Dose–response curves indicated that progressively increasing the proportion of time spent in SP and MVPA ...