Wake-up call for sleep related CVD risk
Geneva, Switzerland - Those who sleep badly, and not for long, have a 65% increased risk of cardiovascular disease—and an even greater risk of coronary heart disease—compared with normal sleepers, according to new research presented at the EuroPRevent 2011 meeting this past weekend.
Researcher Marieke Hoevenaar-Blom (National Institute for Public Health and the Environment, Bilthoven, the Netherlands) explained that several investigations have found an increased risk of CVD in short sleepers compared with normal sleepers, but this is the first study to take into account whether people rise feeling rested. The results should help confirm that suboptimal sleep is a risk factor for cardiovascular disease, something she says is not widely appreciated in the cardiology community.
Hoevenaar-Blom, who is studying for a PhD in primary prevention of cardiovascular disease by lifestyle, reported her findings from 12 years of follow-up in a Dutch cohort during an oral session; she was nominated for a young investigator award for her research, which has also been accepted by the journal Sleep for publication .
"The message is that you have to assess sleep, and especially sleep quality, when you see a patient, because it might be a risk factor for cardiovascular diseases," Said Hoevenaar-Blom "When a patient is sleeping poorly, you can very easily fix that," she noted, although she acknowledged that this involves figuring out what is causing the sleep disturbance. However, simple advice—such as restricting intake of caffeinated drinks after a certain time and not watching TV late—can often be useful, she suggested.
Is sleep quality a modifying factor in association with CVD?
In the Monitoring Project on Risks Factors and Chronic Diseases in the Netherlands (MORGEN) study, Hoevenaar-Blom and her colleagues explored the combined associations of sleep duration and quality with CVD and CHD incidence.
The message is that you have to assess sleep, and especially sleep quality, when you see a patient, because it might be a risk factor for cardiovascular diseases.
Information on sleep duration and quality was obtained by a self-administered questionnaire filled in by 20 432 participants (9217 men and 11 215 women aged 20 to 65 years) between 1993 and 1997. Over 10 to 15 years of follow-up, data on morbidity and causes of death were obtained through linkage with several national registries.
Average sleep duration was assessed by asking participants how many hours of sleep they usually got in a 24-hour period. Short sleep duration was defined as six hours or less, while long sleep duration was sleeping for nine hours or more per 24-hour period. Sleeping for seven to eight hours was designated "normal." Sleep quality was assessed in the first two years of baseline measurements with the question, "Do you usually rise feeling rested?"
"Our research questions were: 'What is the association between sleep duration and cardiovascular disease and coronary heart disease? And is sleep quality a modifying factor in this association?' " Hoevenaar-Blom explained.
After 10 to 15 years of follow-up (mean 11.9 years), 1486 participants developed CVD, of whom 177 had a fatal event. After adjustment for multivariate confounders, short sleepers had a 15% higher risk of incident CVD compared with participants with normal sleep duration, a finding that was significant, and short sleepers had an even stronger, 23% higher risk of CHD compared with normal sleepers.
It's not just quantity, but quality, that is important
On its own, no association was found between sleep quality and CVD incidence, but when assessing quality in combination with sleep duration, short sleepers with poor-quality sleep had a 65% higher risk of CVD and an 85% higher risk of CHD than participants with a normal sleep duration and good sleep quality.
The investigators found no association between long sleep duration and CVD, a finding that contradicts previous studies, said Hoevenaar-Blom. She noted that there has never been any biological mechanism to explain why people who sleep longer have increased risk, but she hypothesized it could be due to reverse causality—that these people were perhaps ill in the first place and therefore slept longer.
Asked whether psychosocial stress could be contributing to poor sleep quality and short duration of sleep, she acknowledged that, of course, this was likely. "We do need more research," she observed.
"In conclusion, short sleepers have an increased risk of total CVD and CHD; the risk in short sleepers is the largest when they are not rising rested; it's really the combination" that is important, she said.
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