The impact of major affective disorders on the effectiveness of diabetes prevention programs at promoting health behaviors has not been established. We investigated whether depression modifies the effectiveness of two pragmatic diabetes prevention programs at promoting increased physical activity.
This study pooled data from two cluster randomized controlled trials (Walking Away from Type 2 Diabetes and Let’s Prevent Type 2 Diabetes) that included individuals at high risk of type 2 diabetes who were recruited from primary care. The trials used very similar intervention methods to promote physical activity and had annual follow-up over a 36-month period. Depressive symptoms were measured by the Hospital Anxiety and Depression Scale, and physical activity was measured by a piezoelectric pedometer (Let’s Prevent Type 2 Diabetes) or an accelerometer (Walking Away from Type 2 Diabetes) and expressed as steps per day.
This analysis included 1,163 individuals (571 control, 592 intervention) who had concurrent baseline and follow-up data for ambulatory activity, depression, and anxiety. The median depression score was 3 at baseline; 11% of individuals were classified as having mild to severe depression. Those with no depressive symptoms at baseline or during follow-up increased their ambulatory activity by 592 steps per day (P < 0.001); this effect decayed by 88 steps per day (95% CI 21, 155) for every additional depressive symptom score at baseline, and each increase in the depressive symptom score between baseline and follow-up further attenuated the intervention effect by 99 steps per day (95% CI 2, 196).
Both depressive symptom burden at baseline and change in this burden are associated with a graded reduction in the effectiveness of diabetes prevention programs at increasing physical activity in primary care.