Sleeping after midnight is bad for your health, so is going to bed before 10pm, finds study

Study, which observed 1.12 lakh participants across 21 countries for nearly a decade, said early and late sleepers have a higher risk of heart attacks, strokes, and even death.

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New Delhi: Sleeping early (10 pm or earlier) could increase incidents of heart attacks, strokes and death by nearly 9 per cent, according to a new study. Among those who slept late (midnight or later), the risk factor could increase by 10 per cent.

Published in the medical journal Sleep Medicine earlier this month, the study noted how early or late bedtimes could be an indicator or risk factor for adverse health outcomes such as cardiovascular diseases.

The study was conducted over a period of 9.2 years, during which time sleeping habits of 1,12,198 participants across 21 countries were recorded based on self-reported habitual time of going to bed. Those with a 10 pm bedtime or earlier were categorised as “earlier” sleepers, while participants who went to bed at midnight or later were termed “later” sleepers.

The scientists found a “U-shaped” association between bedtimes and the possibility of stroke, heart failure and death. Using people going to bed between 10 pm and midnight as a reference group, and after adjustment for age and sex, it was found that both earlier and later sleepers had a higher risk of adverse health outcomes.

The study recorded a total of 5,633 deaths and 5,346 major cardiovascular events over the course of 9.2 years.

The study was conducted by 23 scientists, including three Indians — Dr V. Mohan, chairman and chief of diabetology at Dr Mohan’s Diabetes Specialities Centre in Chennai, Dr Khalid F. Alhabib from Eternal Heart Care Centre & Research Institute in Jaipur and Dr Biju Soman from Sree Chitra Tirunal Institute for Medical Sciences and Technology in Thiruvananthapuram, who also works for the not-for-profit called Health Action by People.

‘Body’s internal clock gets affected’

Sleeping early or late, the study said, adversely affects the body’s internal clock or what is known as ‘circadian rhythm’ — a natural process that regulates sleep-wake circle — and certain metabolic processes.

Earlier sleepers, the study further noted, were slightly older, less educated, more likely to be women and living in rural areas. They slept more, smoked and drank less, consumed less energy, had lower BMI (body mass index), were more hypertensive but less diabetic and depressive. Later sleepers were the opposite.

The study also stated that participants from low and middle-income countries “like China” were more likely to be earlier sleepers, while those from high-income countries and regions “like North America and the Middle East” had later bedtimes.

The study mentioned that in “the fully adjusted model” — where demographic factors, lifestyle behaviors such as total sleep duration, and history of diseases were included — results were “greatly attenuated” but the estimates indicated modestly higher risks in both earlier and later sleepers.

In December 2018, a similar study published in the European Heart Journal had found that the amount of time a person sleeps, including naps during the day, is linked to risk of developing cardiovascular disease and death. Over 1,16,000 people in seven regions of the world were studied at the time.