Will Turning Off Your Bedroom Lights Make You Lighter?Friday, January 18, 2013
Now, a paper by Kenji Obayashi from the Nara Medical University (Japan), published in the Journal of Clinical Endocrinology and Metabolism, takes this issue one step further.
The researchers looked at the relationship between intensity of light in the bedroom, BMI and other variables in 528 elderly individuals.
Compared with the individuals with no to very low night-time light exposure (<3 lux – note: a full moon night is about 1 lux, twilight is about 3 lux), those with higher exposure (average ≥3) were significantly heavier (by about 4 lbs), had about one unit higher BMI, and about two cms larger waistlines. Individuals with greater light exposure, were almost twice as likely to meet BMI criteria for obesity.
These associations were independent of numerous potential confounders, including demographic and socioeconomic parameters.
Obviously, the meaning of these data are far from conclusive and it would be premature to draw any inferences regarding causality.
It may however be plausible to hypothesize that even minimal amounts of night-time light exposure can affect quality of sleep, thereby in turn, affecting metabolism (in ways in which we now know sleep-deprivation to do).
It would certainly be of interest to see how such findings can be reproduced in a more experimental setting – I would not be surprised if these findings can be confirmed and further highlight the importance of ensuring not only adequate duration but also quality of sleep.
Obayashi K, Saeki K, Iwamoto J, Okamoto N, Tomioka K, Nezu S, Ikada Y, & Kurumatani N (2013). Exposure to Light at Night, Nocturnal Urinary Melatonin Excretion, and Obesity/Dyslipidemia in the Elderly: A Cross-Sectional Analysis of the HEIJO-KYO Study. The Journal of clinical endocrinology and metabolism, 98 (1), 337-44 PMID: 23118419