Short sleep is a questionable risk factor for obesity and related disorders: Statistical versus clinical significance

Habitually insufficient sleep could contribute towards obesity, metabolic syndrome, etc., via sleepiness-related inactivity and excess energy intake; more controversially, through more direct physiological changes. Epidemiological studies in adult/children point to small clinical risk only in very short (around 5 h in adults), or long sleepers, developing over many years, involving hundreds of hours of 'too little' or 'too much' sleep. Although acute 4 h/day sleep restriction leads to glucose intolerance and incipient metabolic syndrome, this is too little sleep and cannot be sustained beyond a few days. Few obese adults/children are short sleepers, and few short sleeping adults/children are obese or suffer obesity-related disorders. For adults, about 7 h uninterrupted daily sleep is 'healthy'. Extending sleep, even with hypnotics, to lose weight, may take years, compared with the rapidity of utilising extra sleep time to exercise and evaluate one's diet. The real health risk of inadequate sleep comes from a sleepiness-related accident. (C) 2007 Elsevier B.V. All rights reserved.