Irrespective of ethnic and socio-cultural background, human sleep is synchronised with the lunar cycle.

The team had used wrist monitors on 98 individuals to track their sleeping pattern and this research was conducted in three communities in Argentina.

from http://www.firstpost.com/tech/science/irrespective-of-ethnic-and-socio-cultural-background-human-sleep-is-synchronised-with-the-lunar-cycle-9262491.html