Long hours of work, insufficient sleep, and risk of heart attack

A recent study found that people who frequently work long hours or get little sleep are at twice the risk of suffering a heart attack. The researchers from the Department of Epidemiology, Medical Research Institute, Tokyo Medical and Dental University, Japan carried a study to examine the relation between working hours and hours of sleep and the risk of acute myocardial infarction (AMI) or non-fatal heart attacks in Japanese males with special reference to the joint effect of these two factors. They evaluated the cases of 260 men aged 40 to 79 who were admitted to hospitals with AMI during 1996–98. The men were matched to a "control" group of 445 men similar in age and residence who had not had heart attacks. Then they compared the number of work hours all the men had put in during the previous year, as well as their daily hours of sleep. They also took into account other possible risk factors, such as smoking, alcohol consumption, body weight and disease history. Men who worked 61 hours a week or more, on average, during the past year were twice as likely to have a heart attack as the men who worked 40 hours a week or less. And the men who slept for 5 hours or less, on average, each working day during the previous year had twice the heart attack risk of men who got more than 5 hours of sleep. Also, the researchers found, sleep deprivation in the previous week and lack of more than 2 days off in the previous month boosted heart attack risk even further, suggesting that lack of rest may have a short-term effect as well as a long-term one. The stress of long work hours may throw off the heart's normal rhythm, which can lead to a heart attack. These findings suggest that chronic overwork and sleep deprivation confer increased risk of heart attack and that recent lack of rest and sleep deprivation may further enhance the risk. It would be desirable to limit work to 40 hours or less a week, and to ensure that people who do work long hours get enough sleep.