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Thursday 20th June 2019

Lights before bed could affect sleep

17th January 2011

New research from the United States has found that having the lights on before bedtime could spoil a good night's sleep.


The study found that the body produces less of the hormone melatonin, which regulates the body's daily rhythms of sleep and wakefulness, if there is light in the immediate environment.

Writing in the Journal of Endocrinology and Metabolism, the researchers warned that disturbed sleep patterns have been linked to some types of cancer, blood pressure and diabetes.

Shift workers who took part in the study were also found to have lower levels of melatonin, the production of which begins in the pineal gland when darkness falls.

The human body seems dependent for its well-being on a regular day/night rhythm, regardless of modern lifestyles.

However, switching on lights in the home was found to switch off the hormone's production process, according to the study carried out jointly by the Brigham and Women's Hospital and Harvard Medical School.

For the purposes of the research, 116 people had their sleep, and the amount of light they received, controlled in a room over a five-day period.

Each participant had 16 hours awake and eight hours' sleep in any 24-hour period.

The people were exposed to 16 hours of room light during their waking hours, initially, moving to just eight hours of room light in the morning and eight hours of dim light in the evening.

There was a clear link between electrical light between dusk and bedtime, and strongly suppressed melatonin levels, the team found.

The participants who had dim light in the evening produced 90 more minutes' worth of melatonin in a day.

Lead author Joshua Gooley said the study showed that exposure to indoor light had a strong suppressive effect on the hormone melatonin.

He said suppressed melatonin production could have effects on sleep quality and the body's ability to regulate body temperature, blood pressure and glucose levels.

He said the study findings could have important health implications for shift workers, as keeping the lights on through the night also reduced the amount of melatonin produced.

He added that chronic light suppression of melatonin had been hypothesised to increase relative risk for some types of cancer, while melatonin receptor genes had been linked to type 2 diabetes.

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