Men that work 60 or more hours a week and do not get regular sleep may double the risk of having a heart attack, according to a new report published in the July issue of the journal Occupational and Environmental Medicine.
The study, conducted from 1996 to 1998, focused on 260 men between the ages of 40 and 79, who had been admitted to a hospital for a first time heart attack. A comparison group of 445 men with no history of heart attack, but matched for age and residence were also investigated.
All the men completed a questionnaire detailing their weekly working hours, number of days off, and daily hours of sleep within the past month and over the past year. Details of potential risk factors for heart attack were also obtained, including lifestyle, weight, and conditions such as high blood pressure, high cholesterol, and diabetes.
The study found longer working hours were associated with fewer days off and shorter amounts of sleep, including more days with five hours of sleep or less for both groups of men. But the men who had experienced a heart attack worked significantly longer, slept less, and slept for five or fewer hours a night significantly more often than the men in the comparison group.
The researchers also report weekly working hours in the past year as well as in the past month were linked to progressively increased risk of having a heart attack. Men working 60+ hours a week had double the risk of men working 40 or fewer hours.
An average night’s sleep of five or fewer hours, and for two nights of the working week, was associated with a doubling, and even, tripling, of the risk. Frequent lack of sleep and fewer days off in the preceding month also significantly increased the chances of having a heart attack, and more so than equivalent events in the past year. The authors suggest that sleep deprivation and lack of rest in the very recent past may act as triggers.
Overtime and lack of sleep affect heart health in that they can increase blood pressure and heart rate while chronic stress may induce abnormalities in heart function. The authors suggest that the combination of the two could increase sympathetic nervous system activity to the point where it triggers a heart attack.
The researchers conclude that the optimal working week is a maximum of 40 hours. Those who work longer should make sure they get sufficient sleep and have at least two days rest a month.