Trajectories of objectively measured physical activity and mood states in older Japanese adults: longitudinal data from the Nakanojo Study.

Background: Japan, like many developed countries, now faces fiscal problems from the escalating health-care expenditures associated with an aging population. Mental health problems such as depression contribute as much to these growing demands as physical disease, and measures to prevent depression are important to controlling costs. There are few longitudinal studies examining the relation between objectively measured physical activity and depressive symptoms. Therefore, the aims of our study were to explore the patterns of change of physical activity in older Japanese adults for 5 years through the use of trajectory analysis and to examine the relation between physical activity trajectories and depressive mood states.

Main Body: Ninety-two male and 99 female volunteers aged 65-85 years were asked to equip themselves with an electronic accelerometer with a 60-day storage capacity for at least 5 years. The parameters calculated each July for the 5 years were the average daily step count and the average daily duration of activity > 3 METs (moderate to vigorous physical activity: MVPA). Hospital Anxiety and Depression Scale (HADS) assessed corresponding mood states (HADS-A and HADS-D). Trajectories of the accelerometer data were analyzed and fifth-year HADS-D and HADS-A scores were compared among trajectory groups using an analysis of covariance (ANCOVA) that controlled for baseline scores and for baseline scores and age. Six and five distinct trajectories were identified for daily step count and for daily duration of MVPA, respectively. Using ANCOVA controlling for baseline scores, HADS-D scores differed significantly among trajectory groups classed by daily duration of MVPA (p = 0.04), and Tukey's multiple comparison tests showed significant differences between group 2, whose pattern was stable with the middle duration of MVPA, and group 1, whose pattern was stable with the lowest duration of MVPA (p = 0.02), while the results were not significant controlling for both baseline scores and age.

Conclusions: Older people with less MVPA continued to do less MVPA over the 5 years of study, which may be related to a future more depressive mood. Further clinical studies will be necessary to clarify these findings.