Prolonged sitting may increase diabetes risk in physically inactive individuals: an 11 year follow-up of the HUNT Study, Norway

Bjørn O. Åsvold, Kristian Midthjell, Steinar Krokstad, Vegar Rangul, Adrian Bauman

We examined the association between sitting time and diabetes incidence, overall and by strata of leisure-time physical activity and BMI. We followed 28,051 adult participants of the Nord-Trøndelag Health Study (the HUNT Study), a population-based study, for diabetes incidence from 1995-1997 to 2006-2008 and estimated HRs of any diabetes by categories of self-reported total daily sitting time at baseline. Of 28,051 participants, 1253 (4.5%) developed diabetes during 11 years of follow-up. Overall, sitting ≥8 h/day was associated with a 17% (95% CI 2, 34) higher risk of developing diabetes compared with sitting ≤4 h/day, adjusted for age, sex and education. However, the association was attenuated to a non-significant 9% (95% CI -5, 26) increase in risk after adjustment for leisure-time physical activity and BMI. The association between sitting time and diabetes risk differed by leisure-time physical activity (p Interaction = 0.01). Among participants with low leisure-time physical activity (≤2 h light activity per week and no vigorous activity), sitting 5-7 h/day and ≥8 h/day were associated with a 26% (95% CI 2, 57) and 30% (95% CI 5, 61) higher risk of diabetes, respectively, compared with sitting ≤4 h/day. There was no corresponding association among participants with high leisure-time physical activity (≥3 h light activity or >0 h vigorous activity per week). There was no statistical evidence that the association between sitting time and diabetes risk differed by obesity (p Interaction = 0.65). Our findings suggest that total sitting time has little association with diabetes risk in the population as a whole, but prolonged sitting may contribute to an increased diabetes risk among physically inactive people.