Do we need less sleep when the Sun is shining at night?

Question

I always bring black plastic sheets with me when going North in the Summer to make my bedroom pitch dark, but the local people seem to not be bothered by the Sun at night. However, they do say that they need less sleep, some say that they often can't sleep, get up at 2 am and start their work without being affected by sleep deprivation. Here we can read:

The locals sleep well, as they’ve had a long period to get used to the long hours of daylight as the spring progresses. We do however sleep less, because the light makes us energetic and lively, and elevates our mood, so the body needs less sleep.

I don't understand how this can work on the long term, it seems to me that a prolonged period of sleeping less will drain your energy levels.

Answer 1

The National Center for Biotechnology Information made similar observations:

At Arctic and Antarctic latitudes, personnel are deprived of natural sunlight in winter and have continuous daylight in summer: light of sufficient intensity and suitable spectral composition is the main factor that maintains the 24-h period of human circadian rhythms ... A few people desynchronize from the 24-h day (free-run) and show their intrinsic circadian period, usually >24 h.

Basically what you're observing is a group of people who have sufficiently acclimated to their enviroment such that they're operating on a circadian rhythm that is somewhat independent of the sun.

For reference:

Often referred to as the "body clock", the circadian rhythm is a cycle that tells our bodies when to sleep, rise, eat--regulating many physiological processes. This internal body clock is affected by environmental cues, like sunlight and temperature.