Monday, March 12, 2012

Sleep Duration, Sleep Quality, and Cardiovascular Disease

Epidemiological studies have linked short sleep duration, usually defined as less than 6 hours per night, with cardiovascular disease (CVD). However, it is not know whether short sleep duration itself, or if poor sleep quality with shorter sleep duration accounts for the relationship to CVD. In the Journal Sleep is an article where researchers investigated this relationship in a large study carried out in the Netherlands in the 1990's.

Information on sleep quality and sleep duration was obtained by a survey, not measured via sleep studies. Researchers also assessed educational level, smoking status, physical activity, alcohol and caffeine consumption, subjective health, and CVD risk factor medication via self-administered questionnaire.

The results showed that short sleepers had a 15% higher risk of total CVD and a 23% higher risk of coronary heart disease (CHD) when compared to normal sleepers and after adjustment for relevant co-variables. Those with short sleep duration AND poor sleep quality had a 63% higher risk of total CVD and a 79% higher risk of CHD. Short sleepers with good sleep quality and those with long sleep duration (defined as >9 hours of sleep per night) did not have an increased risk of total CVD or CHD.

The take home message is that the duration of sleep is only part of the problem. Some people don't need 8 hours of sleep. But if you sleep about six hours or less, AND that sleep is broken up or non-restorative, you could have increased risk for cardiovascular disease. You should consider seeing your doctor or consulting with a sleep physician.

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