Once you have your food selection sorted, exercise and sleep organised you should add a further healthy habit to your ongoing self-care routine – turning off the lights! A new study reported in the Cell Press Journal Current Biology on July 14 2016 shows many negative health consequences for mice kept under conditions of constant light for a period of months.[1]
Lead author Johanna Meijer of Leiden University Medical Centre in the Netherlands states:
“Our study shows that the environmental light-dark cycle is important for health,” “We showed that the absence of environmental rhythms leads to severe disruption of a wide variety of health parameters.”
Those parameters included pro-inflammatory activation of the immune system, muscle loss, and early signs of osteoporosis. The researchers say that the observed physiological changes were all indicative of “frailty” as is typically seen in people or animals as they age. But there was some more encouraging news.
“The good news is that we subsequently showed that these negative effects on health are reversible when the environmental light-dark cycle is restored,” Meijer says.
As part of the investigation mice were exposed to a constant 24-hour light source. Studies of the animals’ brain activity showed this exposure reduced the normal rhythmic patterns in the brain’s central circadian pacemaker of the suprachiasmatic nuclei (SCN) by 70 percent.
Strikingly, the disruption to normal light and dark patterns and the circadian rhythm led to a reduction in the animals’ skeletal muscle function as measured in standard tests of strength. Their bones showed signs of deterioration, and the animals entered a pro-inflammatory state normally observed only in the presence of pathogens or other harmful stimuli. After the mice were returned to a standard light-dark cycle for 2 weeks, the SCN neurons rapidly recovered their normal rhythm, and the animals’ health problems were reversed.
The findings suggest that more care should be taken in considering the amount of light exposure people get, particularly those who are aging or otherwise vulnerable. That’s important given that 75 percent of the world’s population is exposed to light during the night. Constant light exposure is very common in nursing homes and intensive care units, and many people also work into the night.
Meijer states:
“We used to think of light and darkness as harmless or neutral stimuli with respect to health. We now realise this is not the case based on accumulating studies from laboratories all over the world, all pointing in the same direction. Possibly this is not surprising as life evolved under the constant pressure of the light-dark cycle. We seem to be optimised to live under these cycles, and the other side of the coin is that we are now affected by a lack of such cycles.”
The bottom line, according to the researchers is “light exposure matters.”
Comment
I suspect that if you are reading this and considering your life, that excluding light at night is quite hard, sensible decisions concerning the quality of curtains, absence of electronic displays and no lights left on may be enough, others may benefit further from eye masks or changing of their environment.
Reference
[1] Lucassen EA, Coomans CP, van Putten M, de Kreij SR, van Genugten JH, Sutorius RP, de Rooij KE, van der Velde M, Verhoeve SL, Smit JW, Löwik CW, Smits HH, Guigas B, Aartsma-Rus AM, Meijer JH. Environmental 24-hr Cycles Are Essential for Health. Curr Biol. 2016 Jul 13. View Full Paper
