Abstract
AIMS/HYPOTHESIS: This work examined the role of physical activity in the course of diabetes using data spanning nearly three decades. Our first aim was to examine the long-term association of moderate and vigorous physical activity with incidence of type 2 diabetes. Our second aim was to investigate the association of moderate-to-vigorous physical activity post-diabetes diagnosis with subsequent risk of all-cause and cardiovascular disease mortality. METHODS: A total of 9987 participants from the Whitehall II cohort study free of type 2 diabetes at baseline (1985-1988) were followed for incidence of type 2 diabetes, based on clinical assessments between 1985 and 2016 and linkage to electronic health records up to 31 March 2017. We first examined the association of moderate and vigorous physical activity measured by questionnaire in 1985-1988 (mean age 44.9 [SD 6.0] years; women, 32.7%) with incident type 2 diabetes, using the interval-censored, illness-death model, a competing risk analysis that takes into account both competing risk of death and intermittent ascertainment of diabetes due to reliance on data collection cycles (interval-censored). The second analysis was based on individuals with type 2 diabetes over the follow-up period where we used Cox regression with inverse probability weighting to examine the association of moderate-to-vigorous physical activity after diagnosis of type 2 diabetes with risk of all-cause and cardiovascular disease mortality. RESULTS: Of the 9987 participants, 1553 developed type 2 diabetes during a mean follow-up of 27.1 (SD 6.3) years. Compared with participants who were inactive in 1985-1988, those who undertook any duration of moderate-to-vigorous physical activity had a lower risk of type 2 diabetes (HR 0.85 [95% CI 0.75, 0.97], p = 0.02; analysis adjusted for sociodemographic, behavioural and health-related factors). In 1026 participants with a diagnosis of type 2 diabetes over the follow-up period, data on moderate-to-vigorous physical activity after diabetes diagnosis were available; 165 all-cause deaths and 55 cardiovascular disease-related deaths were recorded during a mean follow-up of 8.8 (SD 6.1) years. In these participants with diabetes, any duration of moderate-to-vigorous physical activity was associated with lower all-cause mortality (HR 0.61 [95% CI 0.41, 0.93], p = 0.02) while the association with cardiovascular mortality was evident only for physical activity undertaken at or above recommendations (≥2.5 h per week of moderate-to-vigorous physical activity or ≥1.25 h per week of vigorous physical activity; HR 0.40 [95% CI 0.16, 0.96], p = 0.04) in fully adjusted models. CONCLUSIONS/INTERPRETATION: Moderate-to-vigorous physical activity plays an important role in diabetes, influencing both its incidence and prognosis. A protective effect on incidence was seen for durations of activity below recommendations and a marginal additional benefit was observed at higher durations. Among individuals with type 2 diabetes, any duration of moderate-to-vigorous physical activity was associated with reduced all-cause mortality while recommended durations of physical activity were required for protection against cardiovascular disease-related mortality. DATA AVAILABILITY: Whitehall II data, protocols and other metadata are available to the scientific community. Please refer to the Whitehall II data sharing policy at https://www.ucl.ac.uk/epidemiology-health-care/research/epidemiology-and-public-health/research/whitehall-ii/data-sharing.