The association between social jetlag, the metabolic syndrome and type 2 diabetes in a 40+year old population: the New Hoorn study

Background and aims: Social jetlag is the discrepancy between our internal circadian clock and social clock and is a measure of circadian misalignment. Previous studies have shown that up to two thirds of the general population, aged 18-35y, suffer from social jetlag and its negative effects on metabolic parameters. As data from the general population over 40+y is missing, the aim of this study is to examine the prevalence of social jetlag and the association between social jetlag, the metabolic syndrome and type 2 diabetes in a 40+yearold, population-based cohort. Materials and methods: We used cross-sectional data from the New Hoorn study cohort, n=1734, 48% male, aged 45-73y. Social jetlag was measured using a questionnaire, calculated as the difference in mid-point sleep on week and weekend days and defined as 0-1h, 1-2h or >2h social jetlag.Metabolic syndrome was defined according to the Adult Treatment Panel III, including waist circumference, hypertension and levels of fasting plasma glucose, HDL-C and triglycerides. Pre-diabetes and Type 2 diabetes were defined according to the WHO guidelines; glucose levels > 6.1 mmol/l, HbA1c > 6% or use of diabetes medication. Results: In our 40+year-old population-based cohort, we observed that only 15% of the unemployed/retired participants had social jetlag of >1h and 65% of the employed participants. In the unemployed/retired group no significant associations were observed between social jetlag status, (parameters of) metabolic syndrome and (pre-)diabetes. However, in the employed group, logistic regression adjusted for age, sex and sleep duration showed a positive association between social jetlag, metabolic syndrome and (pre-)diabetes, with respectively OR 1.1 (95%CI 0.7-1.7) and OR 1.7 (95%CI 1.2-2.4) for participants with 1-2h social jetlag, as well as OR 2.1 (95%CI 1.2-3.6) and OR 2.3 (95%CI 1.5-3.8) for >2h of social jetlag, when compared to participants with 0-1h social jetlag. Conclusion: Social jetlag is associated with metabolic syndrome and (pre-)diabetes in working, 40+year-old participants.