Sleep Longer, Live Longer

There’s been some attention paid recently to how long one should sleep, to derive maximum health benefit. The general conclusion is that, ideally, sleep should last between 7 and 8 hours a night. Now, University of Chicago researchers, writing in the Journal of the American Medical Association, show that sleeping an hour longer each night can lead to a lessening of calcification in the coronary arteries – a predictor of future heart disease.

Almost 500 participants in the Coronary Artery Risk Development in Young Adults (CARDIA), aged between 35 and 47 at year 15 of the study, were found to have no demonstrable coronary artery calcification on CT scans. Data were collected on sleep duration, breaks in sleep, daytime sleepiness, and overall sleep quality, using wrist actigraphy (a tool that monitors rest and activity).

The CT scans were repeated 5 years later, i.e. at year 20 of the study. The researchers found that 61 (12.3%) of the participants had developed coronary artery calcification during this period. Longer sleep duration was significantly linked to reduced calcification – the estimated odds of calcification occurring were lowered by 33% for each additional hour of sleep per night. Other measurements of sleep (quality, breaks, etc) had no such effect. The magnitude of this effect of an extra hour’s sleep was equivalent to that of a reduction in systolic blood pressure of 16.5 mm Hg.

Sleep quantity and quality have been linked with mortality, glucose and appetite regulation, blood pressure, inflammation, obesity, and education, amongst many factors. However, allowances were made for these factors (and many of the others) in the analysis of the results of this study, and they were found to be without influence on the principal finding. Another study, from Japan, has found that less than 7½ hours’ sleep in hypertensive patients is linked to a higher risk of adverse cardiovascular events. Now researchers have to reconcile these findings with those from other studies that suggest sleeping too long is as dangerous to life as sleeping too short a time.