Extremely short or extremely long sleep was associated with increased incidence of preclinical signs of cardiovascular disease in a large cross-sectional study of healthy and relatively young adults. Poor subjective sleep quality was also associated with early signs of CVD.
Dr. Chan-Won Kim of the Sungkyunkwan University in Seoul, South Korea, and his coinvestigators gathered self-reports of sleep quality and sleep duration from 47,309 healthy adults who underwent regularly scheduled physical examinations. Of those, 29,203 adults, 81% of whom were male, had measurement of coronary artery calcification (CAC); while 18,106 patients, 69% of whom were male, underwent brachial-ankle pulse wave velocity (baPWV) measurement. The patients were relatively young, with a mean age of 42 years for the CAC cohort and 46 for the baPWV cohort.
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Coronary artery calcification and distal arterial stiffness are considered to be markers for preclinical CVD; by measuring these markers in a relatively young cohort, the investigators sought to avoid the many confounders that complicate the association between CVD and sleep in older patients with more comorbidities.
The study used multivariable analysis to control for factors such as smoking and alcohol use, marital status and education attainment, and physiologic variables including blood pressure, body mass index, and cholesterol.
Overall, more than 80% of subjects reported good subjective sleep quality, regardless of duration. However, women who reported poor sleep had a higher incidence of CAC, and men with poor sleep had a higher mean baPWV.
For sleep duration, Dr. Kim, Dr. Chang, and their colleagues found a U-shaped association between sleep duration and CAC and baPWV. Compared with individuals who slept 7 hours per night, individuals who reported sleeping less than 5 hours nightly had a CAC score ratio of 1.50, and an increase in baPWV of 6.7 cm/sec. At the other extreme, those who slept 9 or more hours per night had a CAC score ratio of 1.72 and an increase in baPWV of 9.6cm/sec. All these differences were statistically significant (Arterioscler Thromb Vasc Biol. 2015 Sept 10; doi: 10.1161/ATVBAHA.115.306110.).
The results help clarify that the previously known associations between sleep duration, quality, and CVD risk are not fully attributable to the comorbidities that can affect both sleep and heart health, said Dr. Kim and associates. Though they encourage further study to delineate sleep’s contribution to CVD, their results “underscore the importance of adequate sleep quantity and quality, and support the need for considering subjects with extreme duration or poor subjective quality of sleep at high risk for CVD,” they said.
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