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Sleep is as important for health as a nutritious diet and regular exercise. But not too many people seem to realize this—or act on this realization.

Manvir Bhatia, head of department, sleep medicine, and senior consultant, neurology, Saket City Hospital, New Delhi, says that while the exact amount of sleep every individual needs may vary, the guidelines issued by the US-based National Sleep Foundation list a minimum and maximum range. For adults, it recommends 7-9 hours every night, but adds that anywhere between 6-11 hours may be appropriate.

“Not sleeping enough can be detrimental to health in multiple ways, including fatigue and lowered productivity. It usually results in morning headaches, a tendency to fall asleep during the day—during meetings, while watching TV, even while driving," says Vivek Nangia, director and head of department, pulmonology and sleep medicine, Fortis Flt Lt Rajan Dhall Hospital, Vasant Kunj, New Delhi.

That’s not all. A 2013 study, published in the Proceedings Of The National Academy Of Sciences, found that sleep deprivation could disrupt genes. Insufficient sleep—less than 6 hours a night—affects the activity of over 700 genes, associated with controlling the response to stress, immunity and inflammation, says the study. Inflammation is linked to a long list of health problems, including cardiovascular disease, chronic pain, diabetes and cancer.

In keeping with the theme for World Sleep Day on 13 March, “When sleep is sound, health and happiness abound", here’s a round-up of the research on sleep habits. It might just change your mind about how late you should hit the sack.

Detox your brain

According to a 2013 study published in the Science journal, the waste-draining system is 10 times more active during sleep than while awake. This system cleans up the waste products (proteins called amyloid-beta) linked to Alzheimer’s and dementia. Sleep, therefore, is not just an essential restorative function, but one that can help keep these degenerative disorders away. Another study, published last year in the journal Neurology, has shown that people who have sleep apnoea or spend less time in deep sleep may be more likely to have changes in the brain associated with dementia.

Cut cravings

Dr Bhatia explains the relationship between sleep and weight. “More ghrelin plus less leptin equals weight gain. When you are sleep deprived you have more ghrelin (the “go" hormone that tells you when to eat) and less leptin (the hormone that tells you to stop eating)," she says. In a study published in the journal Scientific Reports in February, researchers at the University of Pennsylvania’s Perelman School of Medicine in the US found that skipping just a single night of sleep leads to a shift in brain activity, which sparks a desire to consume not just more calories, but also more fat the following day.

A 2012 study had shown that sleep-deprived people end up eating an average of 549 extra calories each day (if we do the math, it adds up to a gain of about a pound a week). The study was presented at the American Heart Association’s conference, “Epidemiology and Prevention/Nutrition, Physical Activity, And Metabolism 2012 Scientific Sessions", in San Diego, US. “There’s overwhelming evidence of a direct connect between sleeplessness and weight gain," says Dr Bhatia.

Keep diabetes away

“Research has shown that our T-cells (a type of white blood cells) go down if we are sleep deprived and inflammatory cytokines go up," says Dr Bhatia. A study presented last week at the annual meeting of the Endocrine Society in San Diego found that for every 30 minutes of weekday sleep debt, the risk of obesity and insulin resistance—an indicator of diabetes—increased by 17% and 39%, respectively.

Another study, published in February in the Diabetologia journal, reports that lack of sleep can elevate levels of free fatty acids in the blood, accompanied by temporary pre-diabetic conditions. The researchers found that after three nights of just 4 hours of sleep, blood levels of fatty acids, which usually peak and then recede overnight, remained elevated from 4-9am. As long as fatty acid levels remained high, the ability of insulin to regulate blood sugars was reduced, they said.

Boost learning

What would you say if someone told you that you are better off going to sleep after preparing for a presentation instead of staying up at night revisiting it repeatedly?

In a study, researchers at the University of Fribourg, Switzerland, found that sleep helps firm up previously learnt information. The researchers introduced two groups of participants to words of a new language. Half were kept awake learning, half went to sleep while listening to the recordings of words. A few hours later, those who had slept performed better on the tests than those who had stayed awake. The study was published in the Cerebral Cortex journal in June. “Consolidation of memory is a very important function that sleep delivers. Lack of sleep can result in various neurocognitive abnormalities like restlessness, emotional outbursts, memory lapses and anxiety spells," warns Dr Nangia.

Dr Bhatia agrees. She adds that sleep deprivation leads to lower levels of alertness and concentration. “It’s more difficult to focus and pay attention, so one gets more easily confused. Plus, sleep is essential for both learning and creativity. It’s no surprise that people who are well-rested learn better and are more creative," she adds.


Some easy ways to ensure you get proper rest

u Simple steps help. “Keeping dinner light, a light stroll after dinner, a glass of warm milk, keeping TV and computers out of the bedroom go a long way in improving the quality of sleep," suggests Dr Vivek Nangia.

u Napping is a good idea. A short nap can help relieve stress and bolster the immune system of those who slept only 2 hours the previous night, according to a study on men, published in February in the ‘Journal Of Clinical Endocrinology And Metabolism’.

u Avoid stimulants. “Decrease intake of food which are stimulants like tea, coffee, chocolate, nicotine, close to bedtime," says Dr Manvir Bhatia. According to a study published online last month in the ‘Alcoholism: Clinical And Experimental Research’ journal, alcohol may act initially as a sedative, but is actually associated with sleep disruption.

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