Sleep quality in addition to duration needs to be considered in CVD prevention

Short sleepers, especially those with poor sleep quality, have an increased risk of total cardiovascular disease (CVD) and Coronary Heart Disease (CHD) concludes a 15 year Dutch follow-up study (abstract number 10298). The abstract, which has been nominated for a young investigator award at EuroPRevent, is the first study to take rising feeling rested into account when assessing sleep in relation to CVD.Several investigations have found an increased risk of CVD in short sleepers compared to normal sleepers. “However, what these studies didn’t take into account is that for some people short sleep duration may be sufficient to recover, whereas in others it isn’t. Sleep quality may modify the association between sleep duration and CVD,” said Marieke Hoevenaar-Blom, the first author of the study. In the MORGEN (Monitoring Project on Risks Factors and Chronic Diseases in the Netherlands) study, Hoevenaar-Blom and colleagues from the National Institute for Public Health and the Environment (Bilthoven, The Netherlands), explored the combined associations of sleep duration and quality with CVD and CHD incidence. “We hypothesized that the risk of CVD was largest in short sleepers who don’t rise feeling rested in the morning,” said Hoevenaar-Blom. In the study, information on sleep duration and sleep quality was obtained by a self- administered questionnaire filled in by 20,432 participants (9,217 men and 11,215 women) between 1993 and 1997. Over 10 to 15 years of follow-up morbidity data, vital status and causes of death were then obtained through linkage with several national registries. The average sleep duration was assessed by asking participants “How many hours of sleep do you usually get per 24 hour period?” Short sleep duration was defined as sleeping six hours or less; while long sleep duration was sleeping nine hours or more per 24 hour period. Information on sleep quality was assessed in the first two years of baseline measurements with the question “Do you usually rise rested?” After 10 to 15 years of follow-up (mean 11.9 years), 1,486 participants developed CVD of whom 177 had a fatal event. After adjusting for relevant confounders, short sleepers had a 15% higher risk of incident CVD compared to participants with normal sleep duration. On its own no association was found between sleep quality and CVD incidence, but when assessing sleep quality in combination with sleep duration, short sleepers with bad sleep quality had a 65% higher risk of CVD and a 85% higher risk of CHD compared to participants with a normal sleep duration and good sleep quality. The investigators found no association between a long sleep duration and CVD. “Our results show that in preventing cardiovascular events, sleep duration and quality both need to be taken in to account,” said Hoevenaar-Blom. During sleep the body physiologically recovers. “Therefore, those not sleeping according to their needs (short sleep duration and poor quality) don’t entirely recover,” said Hoevenaar-Blom, adding that in future studies more research needs to be undertaken to elucidate the exact mechanism for the relationship between sleep deprivation and CVD. *ESC