Sleeping in a room exposed to ambient light, even at low levels (100 lux), reduces the quality of deep and rapid eye movement (REM) sleep, activates the sympathetic nervous system, and impairs glucose and insulin regulation the following day.

noli's read

This assertion is supported by recent research, notably a study published in PNAS by Phyllis Zee and colleagues. This study (a laboratory RCT) demonstrated that a single night of exposure to 100 lux increased heart rate, insulin resistance, and sympathetic nervous system activity during sleep. Science confirms that even moderate light can penetrate the eyelids and disrupt the circadian rhythm by inhibiting melatonin, which effectively impacts sleep architecture. However, it is important to note that while the immediate metabolic effects are well-documented, the extent of the reduction in deep sleep for any given individual may vary according to their sensitivity to light. Direct long-term extrapolation regarding overall health remains an area of active observation, but the biological mechanism is sound. The advice is therefore based on serious mechanistic and clinical evidence rather than mere intuition.

the sources

1. 1Lan L, Tsuzuki K, Liu YF, Lian ZW. 2017
2. 2Brown TM et al. 2022