Low occupational physical activity is associated with incident type 2 diabetes in overweight and obese individuals: a population-based cohort study

BACKGROUND: Leisure-time physical activity decreases the risk of type 2 diabetes. Whether occupational physical activity affects the risk of type 2 diabetes is still not fully understood. The primary aim of this study was to investigate the association between occupational physical activity and 10-year diabetes incidence in a general adult population in Northern Sweden. The secondary aim was to explore the moderating role of BMI on this association. METHODS: This population-based, longitudinal cohort study included 16,282 diabetes-free individuals aged 28-52 years who participated in a cardiovascular intervention programme in Northern Sweden, and who reported the same occupational physical activity level at baseline and at 10-year follow-up. Incident type 2 diabetes was diagnosed based on oral glucose tolerance testing or a register-based diagnosis. Occupational physical activity was self-reported and categorized as: a) Low: 'Sedentary or standing' or 'Light but partly physically active', b) Moderate: 'Light and physically active', or c) High: Sometimes physically strenuous or 'Physically strenuous most of the time'. Odds ratios (OR) and 95% confidence intervals (CI) for incident diabetes were calculated using multivariable logistic regression analysis, adjusting for age, sex, smoking, education level, family history of diabetes, country of birth, intake of fruits and vegetables, leisure-time physical activity, prediabetes and BMI. Potential interactions between BMI category and T2D were tested using interaction terms in the multivariable model. RESULTS: Six hundred twenty-four individuals developed type 2 diabetes in the 10 years between the first visit and the follow-up. A significant moderation effect of BMI on occupational physical activity was found (p = 0.01). Having a low level of occupational physical activity, compared with a moderate level of occupational physical activity, was associated with an increased risk of incident type 2 diabetes in overweight and obese individuals (OR 1.46, 95% CI 1.09-1.96), but not in those with normal weight (OR 0.80, 95% CI 0.52-1.23). High level of occupational physical activity was not associated with type 2 diabetes (OR 1.12, 95% CI 0.82-1.54). CONCLUSIONS: Low occupational physical activity was associated with incident type 2 diabetes in overweight and obese individuals. Public-health efforts may benefit from encouraging less sitting and standing and more light physical activity during the workday.