Chronotype and mortality - a 37-year follow-up study in Finnish adults

ABSTRACT

The UK Biobank study on chronotype and mortality suggested small increases of all-cause and cardiovascular mortality in a 6.5-year follow-up. Our aim was to constructively replicate findings from it in a longer follow-up. A questionnaire was administered to the population-based adult Finnish Twin Cohort in 1981 (response rate 84%). The study population included 23 854 participants who replied to the question: “Try to assess to what extent you are a morning person or an evening person,” with four response alternatives (anchored from “clearly a morning person” to “clearly an evening person”). Vital status and cause of death data were provided by nationwide registers up to the end of 2018. Hazard ratios for mortality were computed based on 8728 deaths. Adjustments were made for education, alcohol, smoking, BMI, and sleep duration. The covariate adjusted model showed a 9% increase of all-cause mortality for the evening-type group (HR = 1.09, 95% CI 1.01–1.18), with attenuation mainly due to smoking and alcohol. Their importance was highlighted by observing no increased mortality among non-smokers who were at most light drinkers. There was no increase in any cause-specific mortality. Our results suggest that there is little or no independent contribution of chronotype to mortality.

KEYWORDS:

• Chronotype
• diurnal type
• mortality
• longitudinal study
• alcohol
• tobacco
• sleep

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

CH and JK conceived the study, JK conducted analyses, CH drafted the manuscript and JK provided critical comments. Both authors approved the final manuscript.

Data availability statement

The FTC data is not publicly available due to the restrictions of informed consent. However, the FTC data is available through the Institute for Molecular Medicine Finland (FIMM) Data Access Committee (DAC) ([email protected]) for authorised researchers who have IRB/ethics approval and an institutionally approved study plan. To ensure the protection of privacy and compliance with national data protection legislation, a data use/transfer agreement is needed, the content and specific clauses of which will depend on the nature of the requested data.

Publication history

This manuscript was previously published in medRxiv 2022.04.02.22273342; doi: https://doi.org/10.1101/2022.04.02.22273342.

Supplemental data

Supplemental data for this article can be accessed online at https://doi.org/10.1080/07420528.2023.2215342.

Additional information

Funding

JK is supported by the Academy of Finland [grant # 336823] and the Sigrid Juselius Foundation.