Hours lying down per day, as a proxy for sedentary behaviour and risk of diabetes in young and middle-aged adults in Norway: an 11-year follow-up of the HUNT study.

OBJECTIVE

We aimed to examine relationship between hours lying down per day, as a proxy for sedentary behaviour and risk of diabetes in young and middle-aged adults, and to assess if leisure-time physical activity and body mass index (BMI) modified this relationship.

DESIGN

A population-based prospective cohort study.

SETTING

Nord-Trøndelag, Norway.

PARTICIPANTS

The cohort included 17 058 diabetes-free adults, at an age of 20-55 years in 1995-1997, who were followed-up to 2006-2008.

PRIMARY OUTCOME MEASURES

Incident diabetes was defined by self-report of diabetes or non-fasting glucose levels greater than 11 mmol/L at the follow-up.

METHODS

Multivariable logistic regression models were used to obtain OR with 95% CI for risk of diabetes by the categories of hours lying down (≤7, 8 and ≥9 hours/day).

RESULTS

362 individuals (2.1%) developed diabetes during an average of 11-year follow-up. Individuals who reported lying down ≥9 hours/day had an adjusted OR of 1.35 (95% CI 1.01 to 1.80) for incident diabetes compared with those lying down 8 hours/day. Lying down ≤7 hours/day was not associated with the risk of diabetes. In analysis stratified by physical activity, the ORs associated with lying down ≥9 hours/day were 1.41 (95% CI 1.05 to 1.90) and 0.90 (95% CI 0.23 to 3.55), respectively, among the less active and highly active individuals (p=0.048). There was little evidence that the association differed by BMI status (p=0.62).

CONCLUSIONS

Prolonged hours lying down per day was associated with an increased risk of diabetes in young and middle-aged adults. The positive association appeared to be modified by physical activity but not by BMI.