18 Jun Light Exposure during sleep may increase Insulin Resistance
A recent abstract published in the journal of sleep has investigated the effect of artificial light exposure during sleep on melatonin levels and glucose metabolic function. In today’s society, light at night is more and more prevalent, particularly in cities due to street and building lights but also in the bedroom with smart phones and TV’s that may be left on. This study investigated the effects of light during sleep on metabolic function and possible links with type 2 diabetes.
20 adults aged 18-40 years were randomised to Dark-Dark or Dark-Light groups and studied for a 3 day/2 night duration. The participant’s habitual bedtime was determined from 1 week of prior actigraphy and sleep diary data and were allowed 8 hour sleep opportunities each night.
The Dark-Dark group slept in the dark <3 lux on both nights 1 and 2. The Dark-Light group slept in the dark <3 lux on night 1, and with an overhead light of 100 lux on night 2.
Overnight polysomnography and blood samples taken every hour for melatonin were performed. Oral glucose tolerance tests were performed on both mornings of all participants.
The results showed that after a single night of light exposure, there was a significant effect on glucose tolerance tests. The effect was primarily due to increased insulin levels for the Dark-light compared to the Dark-dark group. Insulin resistance is a reduced ability of the body to use insulin. Insulin is the hormone responsible for transporting glucose or sugar out of the blood stream and into the cells for use. This impaired function of insulin precedes type 2 diabetes.
While this is preliminary research data, it is important to recognise the effect of light exposure during sleep on metabolic function. Further studies should be conducted to determine the effect of chronic overnight light exposure during sleep, and if this has long term cumulative effects on metabolic function.