Environmental temperature as a mediator on the association between photoperiod at birth and chronotype

ABSTRACT

The association between chronotypes and season of birth (SOB) remains an inconclusive issue due, in some extension, to the lack of investigations of mediation mechanisms. We evaluated the association of photoperiod at birth (PAB) with chronotypes and sleep duration in Brazil (n = 810), and the mediating effect of meteorological factors, sex, age and rs4753426 polymorphism in the melatonin receptor MTNR1B. Longer PAB was associated with a delayed mid-sleep phase with a suppressive effect of maximum environmental temperature. No significant interactions were identified for the other variables. These findings suggest that photoperiod and environmental temperature modulate chronotype development at early stages.

KEYWORDS:

• SOB
• circadian
• development
• meteorological
• light
• seasonal
• eveningness
• melatonin

Acknowledgements

We thank Dr. André Fermoseli for thoughtful discussions. Research was supported by CAPES, FAPEAL and CNPq. Meteorological data were obtained from the NASA Langley Research Center (LaRC) POWER Project funded through the NASA Earth Science/Applied Science Program.

Declaration of interest

The authors report no conflicts of interest in this paper.