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The importance of sleep

Getting enough sleep is so important for our wellbeing that some sleep experts believe we should pay as much importance to the quality of our sleep as we do to diet and exercise.

In the short term, lack of sleep affects both our mental performance and our mood — it's no surprise that the 2007 Healthwatch survey of 1,200 Australians found that sleep-deprived people reported feeling more stressed, sad, angry, mentally exhausted and less optimistic about their lives as a whole. But there's growing evidence that sleep deprivation may also affect our physical health in a number of ways.

How much sleep do we need each night?

This varies according to age and individual need. However, on average:

  • Most adults need around 7–8 hours, although pregnant women in the first three months of pregnancy may need more
  • Teenagers need about 9–10 hours
  • Primary school children need about 9–10 hours
  • Toddlers need about 10–12 hours sleep at night with naps during the day
  • A newborn baby needs up to 18 hours throughout the day. However, by the time they're a year old this drops to about 11 ½ hours at night with about 1 ½ hours in naps during the day.

How can not enough sleep harm my health?

  • Weight problems. Some sleep experts now suggest that there may be a connection between the increase in our waistlines in recent years and the fact that sleep deprivation is so common. A study published in the Public Library of Science Medicine has shown that people who habitually sleep less than six hours per night are more likely to have a higher than average body mass index (BMI) and that those who sleep for eight hours have the lowest BMIs. While the odd sleepless night won't affect your weight, chronic sleep deprivation might. Research from Spiegel and colleagues at the University of Chicago suggests sleep deprivation may affect hormones that regulate appetite, making us hungrier. Lack of sleep also makes us more tired and less motivated to exercise.
  • Diabetes. Research published in the medical journal Lancet suggests chronic sleep deprivation can affect the body's ability to control blood glucose levels, increasing the risk of diabetes.
  • Depression. Sleep disorders — including insomnia — are now believed to contribute to depression.
  • Lowered immunity. Lack of sleep can make us more infection-prone. In a study published in the Journal of the American Medical Association, when researchers gave the flu vaccine to sleep-deprived students their immune systems produced only half the normal number of antibodies to the vaccine.
  • Effects on blood pressure. Some research by Rosansky and colleagues suggest that just one night of inadequate sleep in people with high blood pressure can lead to raised blood pressure the next day. This effect may help explain the link between poor sleep and heart disease and stroke.
  • Increased heart disease. A US study of over 71,000 women published in the Archives of Internal Medicine found that too little (seven hours or less) or too much sleep (more than nine hours) appeared to raise heart disease risk.
  • Accident and injury. Research by the Australian Transport Safety Bureau found that one in six fatal car accidents involved driver fatigue. The 1989 Exxon Valdez oil spill, the 1986 Challenger space shuttle disaster and the Chernobyl nuclear accident, also in 1986, have all been attributed to human error where sleep-deprivation played a role. Being awake for just 17 hours can lead to a decrease in performance equivalent to a blood alcohol level of 0.05 percent.

What if you have difficulty sleeping?

You may need to change some of your habits to improve your sleep quality and quantity. Have a look at some of our tips for getting a good night's sleep.

If these tips don't seem to help, or if you still have concerns about your sleeping patterns, talk to your doctor who can advise you if you need expert help from a sleep disorders clinic or a sleep psychologist.

Further information

Australasian Sleep Association


Ayas NT White DP Manson JE et al. A prospective study of sleep duration and coronary heart disease in women. Archives of Internal Medicine. 2003; 163(2): 205–209.

Berk M. Sleep and depression — theory and practice. Australian Family Physician. 2009; 38(5): 302–304.

Division of Sleep Medicine at Harvard Medical School. Sleep and disease risk. [online] Boston, MA: President and Fellows of Harvard College. 2007 [accessed 19 Aug 2010] Available from:

Dobbie K. OR 23: Fatigue-related crashes: An analysis of fatigue-related crashes on Australian roads using an operational definition of fatigue. [online] Civic Square, ACT: Australian Transport Safety Bureau. 2002 [last updated 17 Jun 2008, accessed 19 Aug 2010] Available from:

Harvard School of Public Health. Sleep Deprivation and Obesity. [online] Boston, MA: President and Fellows of Harvard College. [accessed 19 Aug 2010] Available from:

MBF. Healthwatch Survey. [online] 2007 [accessed 19 Aug 2010]

Motor Accident Commission. Fatigue. [online] Adelaide, SA: Motor Accident Commission. 2009 [accessed 19 Aug 2010] Available from:

National Sleep Foundation. Sleep-wake cycle — its physiology and impact on health. [online] Washington DC: National Sleep Foundation. 2006 [accessed 19 Aug 2010] Available from: (PDF 2.6Mb)

Rosansky SJ Menacher SJ Whittman D et al. The relationship between sleep deprivation and the nocturnal decline of blood pressure. American Journal of Hypertension. 1996; 9: 1136–1138.

Spiegel K Leproult R L'Hermite-Balériaux M et al. Leptin levels are dependent on sleep duration — relationships with sympathovagal balance, carbohydrate regulation, cortisol and thyrotropin. The Journal of Clinical Endocrinology and Metabolism. 2004; 89(11): 5762–5771.

Spiegel K Leproult R Van Cauter E. Impact of sleep debt on metabolic and endocrine function. Lancet. 1999; 354(9188); 1425–1429.

Spiegel K Sheridan JF Van Cauter E. Effect of sleep deprivation on response to immunization. Journal of the American Medical Association. 2002; 288: 1471–1472.

Taheri S Lin L Austin D et al. Short sleep duration is associated with reduced leptin, elevated ghrelin and increased body mass index. Public Library of Science Medicine. 2004; 1(3): e62.

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This information has been developed and reviewed for Bupa by health professionals. To the best of their knowledge it is current and based on reputable sources of medical research. It should be used as a guide only and should not be relied upon as a substitute for professional medical or other health professional advice.

Bupa Australia Pty Ltd makes no warranties or representations regarding the completeness or accuracy of the information. Bupa Australia is not liable for any loss or damage you suffer arising out of the use of or reliance on the information. Except that which cannot be excluded by law. We recommend that you consult your doctor or other qualified health professional if you have questions or concerns about your health. For more details on how we produce our health content, visit the About our health information page.

Last published 31 October 2010