Sleeping too much or too little seems to increase cardiovascular risk, according to several studies presented during the European Society of Cardiology’s recent meeting in Munich. Indeed, the increased risk may be similar to that associated with smoking or diabetes.

Greek researchers carried out a meta-analysis of 11 studies that followed just over one million patients for an average of 9.3 years. They divided people into three groups: normal (six to eight hours’ sleep), short (less than six hours) and long (more than eight hours). Compared to normal sleep patterns, short and long durations increased the risk of developing or dying from coronary artery disease or stroke (by 11 and 32 per cent respectively).

“Our findings suggest that too much or too little sleep may be bad for the heart,” said lead author Dr Epameinondas Fountas of the Onassis Cardiac Surgery Centre, Athens. “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 second study, from Sweden, followed 759 men aged 50 years for an average of 20.6 years. During this time, 187 men experienced their first major cardiovascular event. Hypertension (24 and 11 per cent), diabetes (5 and 2 per cent), obesity (22 and 11 per cent), current smoking (43 and 30 per cent) and low physical activity (35 and 13 per cent) were all commoner in men who slept for five hours or less a night compared to seven to eight hours.

After adjusting for obesity and diabetes at baseline, men who reported sleeping for five hours or less a night were twice as likely to experience a cardiovascular event (hazard ratio 1.97) than those who slept for seven to eight hours.

“In our study, the magnitude of increased cardiovascular risk associated with insufficient sleep is similar to that of smoking or having diabetes at age 50,” said study author Moa Bengtsson from the University of Gothenburg. “This was an observational study, so based on our findings we cannot conclude that short sleep causes cardiovascular disease, or say definitively that sleeping more will reduce risk. However, the findings do suggest that sleep is important – and that should be a wake-up call to all of us.”

Further evidence emerged from a Spanish study that used actigraphy to measure sleep in 3,974 men and women. Those who slept less than six hours were 21-27 per cent (depending on the assessment) more likely to show asymptomatic atherosclerosis than those who slept seven to eight hours. People who slept for less than six hours were also more likely to show metabolic syndrome.

“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,” said Dr Fountas.

“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.”