A study conducted by the University of Colorado in Boulder and published in the Journal Current Biology was aimed at investigating how widespread availability of electric lighting in modern times, has affected our lives
As all living creatures evolved biological rhythms in tune with sunrise and sunset, electrical light and electrical devices largely interfere with the natural human circadian rhythm.
The researchers analysed two groups of volunteers: the first group was analysed on a normal daily basic routine and their exposure to natural and artificial lighting. The second group was analysed while on a camping trip away from artificial lighting and electrical devices for a week. For both groups, researchers recorded the levels of hormone melatonin, which naturally rises just before we go to sleep to decrease through the night until we wake up.
The researchers observed that the first group tended to stay up until midnight and wake up around 8 in the morning and its melatonin levels were still high up to several hours after they got up, showing they were out of sync with their natural rhythms. However, the second group showed that after a week in a natural environment all the participants sleeping and waking patterns synced with the Sun and they had an increase in sunlight exposure up to 400%. They still slept the same number of hours but the melatonin levels showed they were again in sink with their circadian rhythm.
The researchers concluded that the lighting of the modern environment causes a delay in the circadian rhythm of about 2 hours creating a discordance with our natural rhythm and that natural sunlight exposure during the day helps to recalibrate the biological rhythm.
External Link: Entrainment of the Human Circadian Clock to the Natural Light-Dark Cycle