Not getting enough sleep can do more than just leave you feeling tired. It affects memory, concentration and your ability to deal with the world, making it tough for you to negotiate social situations. It makes you unsympathetic, short tempered and over time, depressed.
New research this week shows that disrupted sleep can affect your mood and behaviour as much as chronic sleeplessness. Waking up several times during the night makes you far more grumpy and depressed than not getting enough sleep, with fitful sleep making people less energetic, unfriendly and depressed the next day than people who slept late, reported researchers in the journal Sleep . Sleep disruptions shorten the periods of deep, slow-wave restorative sleep needed for the brain to feel calm and rested, the study found.
Building block of cell growth
Sleepless nights short-circuit a fundamental cellular process that drives physical growth, physiological adaptation and brain activity. The study, published in the journal, Plant Cell last month, found that protein synthesis – needed for cell renewal and growth -- activity not only changed through of the day, but also did so under the influence of circadian rhythms, the body’s internal sleep-wake cycle that tells you when to sleep and when to get up.
Since muscle action, brain activity, growth and development are controlled by proteins whose synthesis is carefully regulated – for example, infection reduces protein synthesis activity, making you feel sluggish and tired – insomnia-induced changes in synthesis affect the way we function and develop. This makes sleep even more critical for young children and teenagers, who undergo rapid spurts in growth and development.
Nine hours in the land of nod
Few, however, are getting enough sleep. Genetic changes in adolescence shift circadian rhythms to almost three hours later during teenage years, leading to chronic sleep deprivation among young people. Teenagers need about nine hours of sleep each day but average around seven hours, largely because they have to get up in time for school irrespective of when they went to bed. Since circadian rhythms determine when the brain and body are at peak functioning, being forced to follow adult-timetables affects the ability to learn, development and health of young people.
Lack of sleep also leads to weight gain, with several studies showing that those who sleep less than seven hours weighed more than those who slept for nine hours or more. Those who slept between 7 and 8.9 hours each night had a healthy weight.
Delaying bedtime by an hour during the school or workday leads to a two-point increase in body mass index, showed a study of data from 3,342 adolescents between 1994 and 2009 published in the journal Sleep .
Better late than never
A study of first-semester students at Brown University in the US shows that “sleep viability” – how much sleep and wake timing changed each day -- led to students putting on 2kg in just nine weeks, reported a study in the journal Behavioral Sleep Medicine . Unlike adults who usually start their work day around the same time, widely-varying class schedules in college determine when students get up to meet the world, leading to most gaining 2-3 kg of weight – popularly referred to as the ‘freshman pounds’ – in their first year of college.
Concerned that current school and university start times could be irreversibly damaging students mentally and physically, researchers – among them from the University of Oxford, Harvard Medical School and the University of Nevada – suggest classes for students start at 08:30 or later at age 10; 10:00 or later at 16; and 11:00 or later at 18. Writing in the journal, Learning, Media and Technology , researchers say implementing later start times should protect students from chronic sleep deprivation, which are linked to poor learning and growth.
Sleep on it
Truncated sleep raises blood pressure, increases stress hormone levels and causes inflammation, all factors that raise heart disease risk. Chronic sleep deprivation also warps metabolism, causing glucose intolerance and type-2 diabetes. It also causes weight gain by altering metabolic functions, such as how the body processes and stores carbohydrates, and by stimulating the release cortisol, the stress hormone linked to higher amounts of abdominal fat.
The amount of sleep needed varies widely with people, with some making do with six hours a night and others needing up to nine hours. Ideally, adults should target for seven to eight hours of sleep each night, and teenagers go for eight to nine hours. While you don’t need to worry about a sleepless night or two, restless nights for more than two weeks need investigation at a sleep clinic.
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