Moderators of Maintained Increase in Aerobic Exercise Among Aging Men and Women in a 4-Year Randomized Controlled Trial: The DR’s EXTRA Study

BACKGROUND: Little is known about factors that modify the effectiveness of exercise interventions in increasing exercise. We aimed to identify moderators of the effectiveness of aerobic exercise intervention in maintaining increased aerobic exercise among older individuals. METHODS: The participants of a 4-year randomized controlled trial were a population sample of 1410 men and women aged 57 to 78 years. The aerobic exercise group included 185 individuals and the control group included 169 individuals who reported low aerobic exercise at baseline. Maintained increase in aerobic exercise was defined as at least 60-minute increase in moderate-to-heavy aerobic exercise per week from baseline to 2- and 4-year assessments. RESULTS: Individuals in the aerobic exercise group were 2.5 (95% CI 1.5 to 3.9) times more likely to maintain increased aerobic exercise than those in the control group. Individuals aged < 68.5 years but not older individuals succeeded in maintaining increased aerobic exercise in the intervention group (P = .02 for interaction). Individuals who were past smokers (P = .02 for interaction), were working (P = .05 for interaction), or had symptoms of depression (P = .05 for interaction) succeeded better in maintaining increased aerobic exercise in the intervention group than other individuals. CONCLUSIONS: These findings help in more precise targeting of future exercise interventions among older individuals.