Genetic variants for morningness in relation to habitual sleep-wake behavior and diurnal preference in a population-based sample of 17,243 adults

Associations of eveningness with health hazards benefit from analyzing to what extent the polygenic score for morningness correlates with the assessments of the behavioral trait of morningness-eveningness and chronotype. With a population-based sample of 17,243 Finnish adults, aged 25–74 years, this study examines the associations of four feasible assessment methods of chronotype, a) biological the genetic liability based on the polygenic score for morningness (PGSmorn), b) the widely-used single item for self-assessed morningness/eveningness (MEQi19) of the original Morningness-Eveningness Questionnaire (MEQ), c) the behavioral trait of morningness-eveningness as assessed with the score on the shortened version (sMEQ) of the original MEQ, and d) the phase of entrainment as assessed with the habitual midpoint of sleep based on the self-reported sleep-wake schedule during weekend (Sleepmid-wknd) as well as the sleep debt corrected midpoint of sleep (Sleepmid-corr). All self-report measures correlated with each other, but very weakly with the PGSmorn, which explained 1–2% of the variation in diurnal preference or habitual sleep-wake schedule. The influence of age was greater on Sleepmid-wknd and Sleepmid-corr than on the sMEQ or MEQi19, indicating that the diurnal preference might be a more stable indicator for morningness-eveningness than the sleep-wake schedule. Analyses of the discrepancies between sMEQ and MEQi19 indicated that eveningness can be over-estimated when relying on only the single-item self-assessment. The current polygenic score for morningness explains only a small proportion of the variation in diurnal preference or habitual sleep-wake schedule. The molecular genetic basis for morningness-eveningness needs further elucidation.