Sex-specific associations between the lunar cycle and sleep

DOI:https://doi.org/10.1016/j.scitotenv.2021.150222

Commentary

This study uses overnight sleep records from 852 subjects in Uppsala, Sweden, and represents one of the largest polysomnographic examinations of the association of a 53-day long lunar cycle.

Beginning the day after the new moon and continuing into the full moon day, lunar illumination increases and the timing of the lunar meridian gradually shifts from noon to midnight. In contrast, from the day after the full moon to the day of the new moon, the lunar illumination decreases and the lunar meridian timing shifts gradually from early evening towards noon.

These factors led the researchers to focus on the contrast between the waxing and waning periods.

Results showed that sleep duration was shorter at night during the waxing period compared to the waning period (P < 0.001) with a significant interaction effect of participant gender and menstruation on sleep (P < 0.05).

Men were observed to be less sleep efficient (P < 0.001 and P = 0.748, respectively) and to be awake longer after falling asleep at night during the waxing period.

These associations are robust to adjustment for confounding factors, suggesting that the influence of the lunar cycle on human sleep is more pronounced among men.

However, because of the results of this study design, no firm conclusions can be drawn about the causality of the relationship.