background Sleep and physical activity are related, but the direction of this relationship is unclear and it is not known whether the direction differs in depressed and non-depressed persons.
aim To study the bidirectional relationship between physical activity and sleep in daily life by making repeated measurements in depressed and non-depressed people.
method Every day for 30 consecutive days each depressed (N = 27) and non-depressed (N = 27) participant in our study had to complete an electronic questionnaire relating to subjective sleep quality and sleep duration and were required to wear an accelerometer that recorded physical activity.
results Multi-level analysis showed that an increase in subjective sleep duration resulted in a decrease in physical activity. The differences between individuals with regard to the direction and strength of this relationship were significant. Changes in physical activity did not predict changes in sleep quality or sleep duration. We did not find any differences in the relationships for depressed and non-depressed participants.
conclusion Change in sleep duration predicts change in physical activity, although there was significant heterogeneity in the results for individuals. Our findings underline the importance of further research and of the development of interventions that are tailored to the precise needs of the individual patient.