Device-measured physical activity and sedentary behaviour in relation to mental wellbeing: An analysis of the 1970 British cohort study.

Although physical activity and sedentary behaviour have established associations with mental illness, the extent to which they impact on mental wellbeing is not well understood. We examined associations between moderate to vigorous physical activity (MVPA), sitting time (ST) and mental wellbeing in 4526 participants from the 1970 British Cohort Study (UK) in the age 46 survey (2016-18). MVPA and ST were measured using a thigh mounted accelerometer device (activPAL 3 micro) worn continuously for 7 days and participants completed the 14-item Warwick-Edinburg Mental Wellbeing Scale (WEMWBS) to assess mental wellbeing. In linear regression models MVPA (per hr) was associated with an additional 0.57 points on the WEMWBS (95% CI 0.03-1.12) regardless of gender, wear time, education, socioeconomic status, smoking, body mass index, disability and psychological distress. ST was not associated with WEMWBS in the adjusted models (B = -0.11, -0.23, 0.02). In MVPA stratified analyses, ST showed a linear trend with WEMBS in participants with low levels of MVPA but not in medium and high MVPA categories. In this large, nationally representative cohort, device-measured MVPA showed an association with higher mental wellbeing whilst ST was only associated with reduced mental wellbeing in participants with low levels of MVPA. Our main limitation was the cross-sectional design which precludes any inference of direction of association or causality. Nevertheless, interventions to promote MVPA may be an effective public health policy to promote mental wellbeing. Further investigation of the effect different sitting behaviours has on mental wellbeing is warranted.