Even a little light in the bedroom at night is linked to subtle but measurable changes in the structure of the heart, researchers report in the European Heart Journal, using data from the UK Biobank, Bigganchinta reports.

More than 10,000 adults wore light sensors on the wrist for a week, and their hearts were examined by cardiovascular magnetic resonance (CMR). Those with the most light exposure spent on average about 34 minutes a night above 3 lux, roughly three candles a metre from the bed. Their heart walls were about 1.5 per cent thicker, left-ventricular mass about 2.4 per cent higher and contraction about 1.9 per cent weaker.

In a larger analysis of 73,286 people, those most exposed to light at night had, over eight to ten years, a 29 per cent higher risk of heart failure, 15 per cent higher risk of atrial fibrillation, 24 per cent higher risk of myocardial infarction, 33 per cent higher risk of stroke and 26 per cent higher risk of death from cardiovascular disease. Bright daytime light above 1,000 lux showed no such link.

The researchers think night light suppresses the hormone melatonin and disturbs sleep; shorter sleep explained about 25 to 50 per cent of the changes observed. Tulane University epidemiologist Lu Qi said excess light at night is now seen as a possible new risk factor for heart disease.

Because the study is observational, it cannot show that night light alone causes these problems, and more direct research is needed. The researchers advise enough sleep in as dark a room as possible, using blackout curtains or an eye mask if outside light gets in.

Source: Bigganchinta