Dr. Paul Leeson,
Short and long sleep duration are associated with prevalent cardiovascular disease in Australian adults CH. A. Magee et al. J Sleep Res 2011; Advance online publication
There is an Irish proverb that says “A good laugh and a long sleep are the best cures in the doctor’s book”. A research team in Australia appear to disagree. Magee and colleagues looked at questionnaire data from 218,155 Australian adults in the 45 and Up Study based in New South Wales. They found a U-shaped relationship between the amount of self-reported sleep and incidence of cardiovascular disease, stroke and hypertension. The optimal length of sleep was 7 hours with greater incidence of disease in those who slept 6 hours, or over 9 hours. These findings are not novel and have been reported by several groups over the last few years. However, Magee et al. argue the scale of their study allowed them to provide greater precision as to the estimates of the effect, and undertake subgroup analysis. They observed the association between sleep and disease risk was not apparent in those over 75 years and was attenuated in the significantly obese and smokers, in whom rates of disease were substantially higher. There remain significant limitations with this repeated epidemiological observation. Virtually all the reports have been based on self-reported amounts of sleep, which the authors of this paper acknowledge are directly biased by factors such as age, gender and health status. This problem also highlights the fact the data provides no insight into whether the association is causal or secondary to disease. Furthermore, quality of sleep is not taken into consideration, which raises the possibility that Leonardo da Vinci may be closer to the truth with the words: ‘A well-spent day brings happy sleep’.
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