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Many a pop song has nudged us to turn the lights down low, but for cardiovascular health, the better choice seems to be keeping them off entirely, with new research suggesting that pitch-black is best for sleep.
DPA reports that, according to researchers at Tulane University in New Orleans, who looked at health data spanning three years for around 11,000 people in the UK, “even small amounts of nighttime light exposure” can be linked to “potentially harmful changes in the heart’s structure and function.”
Published by the European Society of Cardiology (ESC), the research suggests that even hallway lighting seeping through a door left ajar can have a negative effect. The same goes for light from a phone screen left on a bedside table – a warning that follows multiple studies suggesting that it is best to put phones and screens away well in advance of sleep and avoid bedtime scrolling.
“Light pollution has emerged as a new risk factor for cardiovascular disease,” said Tulane’s Li Qi, who said the findings “should be considered” when it comes to heart disease prevention plans.
Participants wore a wrist sensor for a week to track nocturnal light, with some exposed to 0 lux, or “near total darkness.” Others were put to sleep amid “varying levels of light” up to 3 lux, which the researchers said is around the same as a phone screen at low brightness on a nightstand or a hallway light left on outside a cracked door.
Cardiovascular magnetic resonance scans carried out three years later showed participants exposed to the highest levels of nighttime light had thicker left ventricle walls, meaning less space in the ventricle, along with indications of reduced flexing during heartbeat.
In their paper, which was released in the European Heart Journal, an ESC publication, the researchers noted previous research showing hw light at night leads to “shortening sleep duration” and the disruption of circadian rhythms, which themselves can affect heart functioning.
Sleep disruption, if left unchecked, has in turn been widely linked to cognitive decline and physical ill-health related to effects on the immune system and resistance to inflammation.
“The advice is simple and inexpensive: blackout curtains, warm-coloured bedside lighting, and covering the small standby LEDs on household electronics,” said Thomas Munzel of the University Medical Centre Mainz.
