The amount of sleep a person gets seems to play a defining role in their vascular and heart health, according to researchers presenting at the American College of Cardiology's Annual Scientific Session Together with the World Congress of Cardiology.
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Their study found that compared with a shorter or longer sleep duration, sleeping for seven to eight hours per night was associated with less arterial stiffness, suggesting a reduced risk for heart disease and stroke.
Arterial stiffness is a significant risk factor for and reliable predictor of cardiovascular events and mortality, including among those without symptoms of cardiovascular disease.
The study found that even after adjusting for traditional heart disease and stroke risk factors, individuals with a nightly sleep duration of less than six hours or more than eight hours were at a significantly increased risk for plaque accumulation in the carotid arteries, compared with people who slept for seven or eight hours (at 54% and 39%, respectively).
The study, which included 1,752 people living in Greece, lends further support to the growing body of evidence that sleep duration is a significant contributor to an individual’s risk for cardiovascular disease.
“Sleep well, but not too well”
Lead author and consultant cardiologist, Evangelos Oikonomou, says the take-home message here is “sleep well, but not too well,” since although not getting enough sleep appears to be harmful to health, so does sleeping for too long.
Current guidelines for American adults
Currently, U.S recommendations generally advise that adults sleep for between seven and nine hours per night. However, the Centers for Disease Control and Prevention says that around one-third of adults in the U.S do not sleep for long enough. As well as increasing the risk of heart disease, not getting enough sleep has been associated with an increased risk for hypertension, diabetes, mental health problems, and premature death.
Sleep duration is a modifiable risk factor for heart disease
Oikonomou points out that “unlike other heart disease risk factors such as age or genetics, sleep habits can be adjusted, and even after taking into consideration the impact of established risk factors for atherosclerosis and cardiovascular diseases--for example age, gender, obesity, smoking, hypertension, diabetes, high blood pressure and even a history of coronary artery disease--both short and long sleeping duration may act as additional risk factors."
What did the study involve?
The researchers monitored the sleeping patterns of 1,752 adult individuals aged between 40 and 98 years (mean age 64 years) based on a self-reporting standardized survey that had been provided by health professionals. They then categorized the participants into four groups according to the number of hours they slept per night: normal sleep duration (seven to eight hours); short duration (six to seven hours); very short duration (less than six hours) and long duration (more than eight hours).
The study participants were broadly representative of the general public including healthy individuals and people with and at risk for cardiovascular disease. As well as completing the survey, all participants were given an ultrasound scan to measure carotid intima-media thickness. Atherosclerotic plaque was defined as an intima-media thickness of more than 1.5mm or plaque protrusion of more than 50% compared with surrounding arterial wall segments.
Both too little and too much sleep was linked to cardiovascular risk
The results revealed a U-shaped association between the number of hours slept and the atherosclerosis markers, which Oikonomou says highlights the importance of normal sleep duration.
Both intima-media and plaque accumulation was increased among participants with shorter and longer sleep durations, compared with those in the normal duration group.
Oikonomou says the team does not yet completely understand the association between sleep and cardiovascular health.
“It could be that sympathetic nervous system withdrawal or a slowing [of this system] that occurs during sleep may act as a recovery phase for [usual] vascular and cardiac strain," he suggests. "Moreover, short sleep duration may be associated with increased cardiovascular risk factors--for example, unhealthy diet, stress, being overweight or greater alcohol consumption--whereas longer sleep duration may be associated with a less active lifestyle pattern and lower physical activity."
In the meantime, Oikonomou and colleagues recommend trying to sleep for six to eight hours per night.
"It seems that this amount of sleep may act as an additive cardioprotective factor among people living in modern western societies, and there can be other health benefits to getting sufficient and quality sleep," advises Oikonomou.
Further research is needed
The authors acknowledge that the self-reporting of sleep patterns and the cross-sectional design of the study are limiting factors. However, they believe further investigation is needed, particularly to examine whether excess sleep is detrimental to health because the effects of this have not been as well assessed as the effects of too little sleep.
Bonarjee V. Arterial Stiffness: A Prognostic Marker in Coronary Heart Disease. Available Methods and Clinical Application. Frontiers in Cardiovascular Medicine 2018: https://doi.org/10.3389/fcvm.2018.00064