Evening chronotype is associated with poor work ability and disability pensions at midlife: a Northern Finland Birth Cohort 1966 Study

Objectives This is the first general population study to evaluate whether evening chronotypes (E) have poorer work ability (WA) and higher probability for early disability pensions (DPs) than morning types (M) in middle age. Methods Among non-retired individuals (n=5831; 2672 men, 3159 women) of the Northern Finland Birth Cohort 1966, chronotype was determined at the age of 46 years with shortened Morningness-Eveningness Questionnaires in 2012. The outcomes were poor WA in 2012, indicated by scores 0-7/10 of Work Ability Score, and registered emergence of DPs in 2013-2016. Multivariate logistic and Cox regression analyses were separately adjusted for factors related to sleep, health and behaviours, sociodemographic and economic factors, or working times. Results E-types represented 10% (n=264) of men and 12% (n=382) of women. Compared with M-types, the unadjusted ORs with 95% CIs of poor WA for E-type men and women were 2.24 (95% CI 1.62 to 3.08) and 2.33 (95% CI 1.74 to 3.10), respectively. The odds remained statistically significant and approximately twofold in all separate adjustment models tested. During 2013-2016, 8 (3.0%) E-type men and 10 (2.6%) E-type women were granted DP, which, compared with M-types, represented a higher HR that was statistically significant for men (HR 3.12, 95% CI 1.27 to 7.63) and remained significant except when multiple sleep variables or working times were adjusted for. Conclusions Eveningness appears a previously unrecognised risk factor for poor WA and early disability. We suggest that individual chronotype be considered in attempts to lengthen work careers.