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Slaap en bloeddruk*
Uit een vijfjarige studie onder een kleine 600 mensen blijkt dat het aantal uren slaap per nacht in relatie te staan met de bloeddruk. Uit laboratoriumstudies is al geleken dat er een verband bestaat tussen te weinig slapen en een hogere bloeddruk als gevolg van een toegenomen activiteit van het sympatisch zenuwstelsel. Uit deze studie blijkt nu dat korter slapen inderdaad kan leiden tot een hogere bloeddruk. Ieder uur korter slapen dan zeven uur geeft 37% meer kan op hoge bloeddruk.
A Good Night's Sleep Associated With Reduced Blood Pressure  
More evidence that a good night's sleep is associated with better control of blood pressure has come from a new study [1].
The study, published in the Archives of Internal Medicine, was conducted by a group led by Dr Kristen Knutson (University of Chicago, IL).
Knutson explained to heartwire that previous studies have suggested a link between poor sleep and increased blood pressure but that these have had limitations. "They have generally been short-term laboratory tests, but we wanted to look at the real-life situation and study the effects of habitual sleep patterns. In addition, previous studies that have tried to address longer-term sleep issues have relied on self-reporting of sleep quality, but we measured actual sleep duration and quality using a specifically designed wrist band," she said.
The band, known as an Actiwatch-16 (Philips Respironics, Murrysville, PA) wrist-activity monitor, contains sensors that count wrist movements in 30-second time periods, which determine whether the subject is asleep or awake, and has been validated against polysomnography as a good measure of sleep duration and quality, Knutson commented.
"We found that short sleepers had a larger increase in blood pressure over five years than those who slept longer," Knutson said. "Evidence suggests that a certain amount of sleep is necessary for many different functions in the body, including immune function and glucose metabolism, and if we can extend sleep in those who don't sleep well or for long enough, this should translate into many health benefits--one of which may well be lower blood pressure," she added.
Knutson said it was important to acknowledge the need to spend a certain amount of time asleep. "Five or six hours a night is not enough. Seven hours should really be the minimum. In the US, we have a work culture that discourages decent sleeping patterns. There seems to be a sort of badge of honor associated with sleeping only a few hours each night, and someone who sleeps for seven to eight hours may be perceived as not being hard-working enough. We need to change that culture."
She also believes that those individuals who appear to need only three or four hours of sleep each night may be fooling themselves. "People who sleep for short times do not do well in performance tests, even if they think they are well rested. Even these people should try to increase their sleep times," she said.
The current sleep study was ancillary to the large ongoing cohort CARDIA study, which is examining coronary risk in young adults. For the sleep study, 578 early-middle-aged adults participating in the CARDIA study had their blood pressure measured in 2000 and 2001 and in 2005 and 2006 and underwent sleep assessments using wrist actigraphy on two occasions for three consecutive days between 2003 and 2005.
Results showed that after the exclusion of patients who were taking antihypertensive medications, shorter sleep duration and lower sleep quality predicted significantly higher systolic and diastolic blood pressure at baseline as well as more adverse changes in blood-pressure levels over five years.
Short sleep duration also predicted significantly increased odds of incident hypertension (odds ratio 1.37; 95% CI 1.05–1.78). Each hour of reduction in sleep duration was associated with a 37% increase in the odds of incident hypertension.
Might Explain Higher Blood Pressure in Men and African Americans 
Consistent with other studies, the current results show higher blood pressure in men, particularly African American men, who also slept much less than white women. "These two observations suggest the intriguing possibility that the well-documented higher blood pressure in African Americans and men might be partly related to sleep duration," the researchers write.
The authors note that laboratory studies of short-term sleep deprivation have suggested potential mechanisms for a causal link between sleep loss and hypertension: it is thought that sleep loss may lead to increased sympathetic nervous activity, which could cause high blood pressure if sleep loss were chronic.
They point out that, to their knowledge, the present study is the first to obtain objective measures of sleep duration and quality in a large sample of adults and to reveal associations between poor sleep quality and adverse effect on blood-pressure regulation and risk of hypertension in early-middle-aged adults.
"Because of the major adverse health consequences of high blood pressure, the identification of a new and potentially modifiable risk factor has clinical implications," the authors conclude. "The next step would be intervention studies to try to extend or improve sleep in hypertensive patients and see if we can improve their blood-pressure profile. Such a study is in the works," Knutson told heartwire .
Reference 
1. Knutson KL, Van Cauter E, Rathouz PJ, et al. Association between sleep and blood pressure in midlife. The CARDIA sleep study. Arch Intern Med 2009; 169:1055-1061. Abstract 
Clinical Context
Self-reported short sleep duration and high blood pressure have been linked in epidemiologic studies. However, most of these studies were cross-sectional and relied on self-report of usual sleep duration vs objective measures, and the potential role of sleep quality independent of sleep duration has not been studied in adults.
Potential mechanisms for a causal link between sleep loss and hypertension include increased sympathetic activity. If sleep duration is, in fact, a lifestyle risk factor for high blood pressure, new interventions might be developed to prevent hypertension or reduce high blood pressure.
Middle-aged adults who sleep fewer hours appear more likely to have high blood pressure and to experience adverse changes in blood pressure with time.
Study Highlights
· The CARDIA Sleep Study was ancillary to the CARDIA cohort study.
· The goal was to assess both cross-sectional and longitudinal associations between objectively measured sleep duration and quality with 5-year incidence of hypertension and changes in systolic blood pressure and diastolic blood pressure levels in community-dwelling, early middle-aged adults.
· The study sample for this analysis included 578 African Americans and whites aged 33 to 45 years at baseline (average age, 40.1 years).
· Patients who were taking antihypertensive medications were excluded.
· Participants underwent blood pressure measurement in 2000, 2001, 2005, and 2006.
· Other clinical, demographic and health variables were measured between 2000 and 2001, and demographic and self-reported sleep information was measured again in 2005 and 2006.
· Between 2003 and 2005, participants had 2 sleep evaluations with wrist actigraphy for 3 consecutive days, allowing calculation of sleep duration and sleep maintenance.
· Endpoints of the study were systolic blood pressure and diastolic blood pressure levels, 5-year change in blood pressure, and incident hypertension.
· Average sleep duration was 6 hours per night, and only 1% of participants averaged 8 or more hours of sleep nightly.
· Higher blood pressure levels were seen in men, especially African American men, and this group slept much less vs white women.
· After adjustment for age, race, and sex, shorter sleep duration and lower sleep maintenance predicted significantly higher systolic blood pressure and diastolic blood pressure levels cross-sectionally (all P < .05).
· The associations between sleep and blood pressure were slightly attenuated by adjustment for 16 additional covariates, including snoring and daytime sleepiness.
· Shorter sleep duration and lower sleep maintenance also predicted more adverse changes in systolic blood pressure and diastolic blood pressure levels for 5 years (all P < .05), after adjustment.
· Short sleep duration was associated with significantly increased odds of incident hypertension (odds ratio, 1.37; 95% confidence interval, 1.05 - 1.78).
· The difference between African Americans and whites in diastolic blood pressure change with time appeared to be mediated by sleep duration (P = .02).
· The investigators concluded that reduced sleep duration and maintenance predicted higher blood pressure levels and adverse changes in blood pressure.
· They therefore recommended further research to determine whether interventions to optimize sleep may lower blood pressure.
· Limitations of the study include use of wrist actigraphy, which measures only movement, rather than the criterion standard of polysomnography.
· This study therefore could not address the role of sleep-disordered breathing.
Clinical Implications
· In the CARDIA Sleep Study, shorter sleep duration and lower sleep maintenance predicted significantly higher systolic blood pressure and diastolic blood pressure levels cross-sectionally, after adjustment for age, race, and sex.
· Reduced sleep duration and maintenance in this study also predicted adverse changes in blood pressure with time, including increased odds of incident hypertension. The difference between African Americans and whites in diastolic blood pressure change with time appeared to be mediated by sleep duration. (Juli 2009)