A study presented at the European Society of Cardiology Congress investigated the relationship between sleep duration and cardiovascular disease using a meta-analysis, a statistical tool for combining the results of previous studies on the same topic. The meta-analysis included 11 prospective studies of more than one million adults (1,000,541) without cardiovascular disease published within the last five years.
Study author Epameinondas Fountas, MD, of the Onassis Cardiac Surgery Centre, Athens, Greece, says in a release, “We spend one-third of our lives sleeping yet we know little about the impact of this biological need on the cardiovascular system.”
Two groups, one with short (less than 6 hours) and another with long (more than 8 hours) nightly sleep duration, were compared to the reference group (6 to 8 hours).
The researchers found that both short and long sleepers had a greater risk of developing or dying from coronary artery disease or stroke. Compared to adults who slept 6 to 8 hours a night, short and long sleepers had 11% and 33% greater risks, respectively, of developing or dying from coronary artery disease or stroke during an average follow-up of 9.3 years.
Fountas says, “Our findings suggest that too much or too little sleep may be bad for the heart. More research is needed to clarify exactly why, but we do know that sleep influences biological processes like glucose metabolism, blood pressure, and inflammation—all of which have an impact on cardiovascular disease.”
A strength of the current analysis is that only prospective studies were included, Fountas says. This avoids recall bias, a source of systematic error in statistics arising from the inability of participants to accurately recall information.
Fountas says, “Having the odd short night or lie-in is unlikely to be detrimental to health, but evidence is accumulating that prolonged nightly sleep deprivation or excessive sleeping should be avoided. The good news is that there are plenty of ways to get into the habit of getting six to eight hours a night—for example by going to bed and getting up at the same time every day, avoiding alcohol and caffeine before bed, eating healthily, and being physically active. Getting the right amount of sleep is an important part of a healthy lifestyle.”