If you sleep less than five hours a day, chances are you will put on five kilos within a year and develop diabetes sooner than later.

This unhealthy equation was spelt out in a study done by Harvard University’s Brigham and Women’s Hospital last week. The study also said that people getting less than five hours of sleep or those who worked on night shifts are likely to get diabetes faster than people with day jobs.

“People are ideally supposed to sleep for eight hours a day, work for another eight hours and reserve the remaining eight hours for recreation,” said endocrinologist Shashank Joshi. But Mumbai’s 24x7 grind blurs this rhythm. “We are daily sleeping less and planning to catch up with it over the weekend,” said Dr Joshi, who consults at Lilavati Hospital in Bandra and is researching the sleep-diabetes link in Mumbai.

Working weekends further disrupt this cycle. “Mumbaikars thus live with sleep debt,” Dr Joshi added.

One of Dr Joshi’s research papers underlines the converse of the Harvard study-how sleep is distorted among patients with diabetes. “A student of mine looking at the prevalent sleep habits in 260 patients with diabetes found that almost 24% of them slept less than five hours,” said Dr Joshi.

The Harvard study reinforces increasing medical research that shows disturbed sleep patterns could lead to diabetes. In Mumbai, the under-40 brigade-comprising corporate climbers and entrepreneurs-suffers the most from poor sleep patterns. At sleep expert Dr Preeti Devanani’s clinic in Jaslok Hospital the bulk of the patients are in the under-40 group. “Maybe it is their work or stress. People below 40 years of age suffer from chronic sleep debt and are unable to make up for it. Health problems predictably follow,” she said.

Endocrinologist Archana Juneja from Kokilaben Ambani Hospital in Andheri calls it the bane of the generation that sleeps next to its phone. “They are not only stressed, but also have disturbed sleep and hormone cycles that lead to central obesity. Metabolic syndrome (with elevated lipids) and diabetes follow,” she explained.

The Harvard study, which was published in the new Science Translational Medicine journal, looked at 21 healthy participants for six weeks. The researchers controlled how many hours of sleep participants got as well as when they slept and other factors such as activities and diet. Participants started with getting optimal sleep (approximately 10 hours per night). This was followed by three weeks of 5.6 hours of sleep per 24-hour period and with sleep occurring at all times of day and night, thereby simulating the schedule of rotating shift workers. The researchers saw that glucose concentrations in the blood increased after meals because of poor insulin secretion by the pancreas.

The body’s hormones surge in the wee hours of the morning. “It surges by 4am or so and subsides by evening. People who sleep later than, say, 2am or 3am miss this hormone surge in the body,” said Dr Juneja.

Not surprisingly then, a map of sleep deprivation versus sleep duration would show a bell curve graph. “Anything less than four days or more than 10 hours in a 24-hour cycle is deleterious to health,” said Dr Devnani.

So, sleep deprivation would worsen symptoms for people with heart disease, decrease the production of hormone leptin (which suppresses appetite) and increase the production of hormone ghrelin (which stimulates appetite). “This imbalance in the leptin-ghrelin cycle causes obesity,” Dr Devnani said. Worse, sleep deprivation among people trying to lose weight only results in the body’s good fat getting lost.

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Malathy Iyer - Harvard University