Should leisure time sedentary behaviour be replaced with sleep or physical activity for prevention of diabetes?

The aim was to examine the effects of replacing self-reported leisure time sedentary behaviour with sleep, light-to-moderate, or vigorous physical activity on incident diabetes among Danish adults using isotemporal substitution modeling. Participants ≥ 25 years from the Danish Capital Region Health Survey 2007 (N=69,800, response rate 52.3%), 2010 (N=95,150, response rate 52.3%) and 2013 (N=95.150, response rate 43,5%) were included. Information on daily sleep duration, leisure time sedentary behaviour and movement behaviours was collected by questionnaire. Information on incident diabetes was obtained from National registers. Analyses included Cox proportional hazards regression models and isotemporal substitution analyses, with time (in years) from baseline to incident diabetes or censoring 31 December 2017. Potential confounders, sex, age, BMI, ethnicity, education, smoking, inflammatory joint disease, perceived stress, physical and mental component scale and work status, - were included. Out of N=87,339 in the final study sample, n=3,007 had incident diabetes during a mean follow-up time of 7.4 years. Adults with incident diabetes included more men, higher mean age, and higher BMI, compared to respondents without incident diabetes. Theoretically substituting 30 minutes of leisure time sedentary behaviour with light-to-moderate PA (HR 0.96, 95%CI 0.94; 0.98) or with vigorous PA (HR 0.82, 95%CI 0.72; 0.94) decreased the risk of incident diabetes. We found no change in incident diabetes risk of substituting sedentary time with sleep (HR 1.00 95%CI 0.97;1.02). Substituting 30 min per day of leisure time sedentary behaviour with light-to-moderate or vigorous PA, may significantly reduce the risk of incident diabetes among adults.