Too much sleep as bad as too little: How much sleep do we really need?

  • Sanchita Sharma, Hindustan Times
  • Updated: May 07, 2016 17:07 IST
You should target to sleep between six and seven hours of sleep each night. (Pinterest)

Most of us are convinced we are not getting enough sleep. Just as we believe we need eight hours of sleep each day.

We are wrong on both counts.

Oversleeping causes as much health trouble as insomnia. (Tumblr)

Over the past few decades, several studies have shown that humans need less sleep than we are conditioned to have. Our hunter-gatherer ancestors slept far less than most of us do. A study of people in pre-industrial societies in Tanzania, Namibia and Bolivia show similar sleep patterns, with the duration in both continents ranging between 5.7 and 7.1 hours, reported researchers in the journal Current Biology.

More than light, temperature was found to regulate of how much and when people still living in traditional societies slept. The study of three remote groups—the Tsimané foragers of Bolivia, the Hadza hunter-gatherers of Tanzania, and the San of Namibia showed that all three slept for several hours after sunset and got up before sunrise. All slept an extra hour in winter.

Read: Losing sleep over sleeplessness

Much has been written about the health hazards of insomnia – it raises risk of obesity, depression, anxiety, heart disease, diabetes, infections, some cancers and death -- but too much sleep affects in much the same way

Sleep prescription

So, how much sleep does an average adult need? Going by the availability of natural light, the US National Sleep Foundation recommends seven to nine hours, depending on your age, but studies show seven hours is closer to what healthy adults need. Sleeping for less than 6.5 hours and more than 7.5 hours raises risk of several disease and early death.

A study of more than 1.1 million people over age 30 showed that those who slept for eight hours or more, or less than four hours, had a higher death rate than those who slept for six to seven hours a night, reported a study in the JAMA Psychiatry. Those who slept as little as five hours lived longer than those who got more than eight hours of sleep a night, but those who slept for seven hours lived the longest.

If you know the feeling of contemplating throwing your phone and never working again for the sake of extra sleep, then you’re a chronic sleep lover. But that is not good, science proves. (Tumblr)

Occasional bouts of insomnia and disrupted sleep did not raise the risk of death, but people who took sleeping pills were more likely to die sooner than people who got the right amount of sleep.

Weight gain, heart disease

A very obvious fallout of sleeping too much is weight gain, as you burn less calories while sleeping than you do when you are up and about. Several studies have shown that people who sleep for nine to 10 hours weight 5 kg more than average sleepers even after controlling for food and physical activity, but oversleeping does more than trigger weight gain.

Read: Sleep timely, get up early to have a healthy heart

Too much sleep leads to you putting on a lethal form of fat called ‘visceral fat’, which is stored in the abdomen around internal organs such as the liver, pancreas and intestines. This unsightly belly fat affects hormone function and raises risk of metabolic disorders, such as high cholesterol, diabetes and heart disease, reports a study in the journal Obesity. Women who sleep 9 to 11 hours every night have 38 % higher chances of heart disease than women slept for less than eight, showed the analysis of data from close to 72,000 participants who were tracked for 20 years as part of the Nurses’ Health Study in the US.


You are at a 2½ times higher risk of developing diabetes and glucose intolerance, which is a precursor to diabetes, if you sleep less than seven or more than eight hours each night, reports a study in the journal Sleep Medicine. The study, which tracked people for over six years, found around 20% of those with long- and short-sleepers developed type-2 diabetes or impaired glucose tolerance compared to 7% people who slept for seven hours,. Even after factoring in the differences in lifestyle and weight, the risk of diabetes and insulin resistance remained twice as high among long- and short-sleepers.

Brain drain

While sleeping for seven hours a day keeps your brain sharp in later life, sleeping for nine hours or more lowers brain function, report Harvard researchers in the Journal of American Geriatrics Society. For the study, sleep patterns of women in the Nurses’ Health Study were studied and they were tested for memory and though process 25 years later. Those who slept five hours or fewer per night or nine hours or more, compared with those getting seven to eight hours of sleep a night, did the worst. Under- and over-sleepers were mentally two years older than healthy sleepers, found the study.

Read: Not getting enough sleep? You’re probably a Facebook-addict

All this scientific fodder should make us stop whining about sleeplessness and put the time spent awake to more productive use.

Five steps to better sleep

Set a bedtime and wake-up schedule and stick to it. Don’t delay wake-up time to make up for lost sleep.

Adopt a relaxing bedtime routine, such as reading a book or listening to music. Avoid watching television, using smartphones and e-books in bed as light from backlit-screens affect sleep patterns.

If you can’t fall asleep within 15 to 20 minutes of going to bed, go to another room. Get back to bed only when you’re sleepy.

When possible, schedule stressful activities early in the day and less challenging activities later to help you wind down.

Don’t eat a big meal at night.

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