Those long hours you're putting in at the office could very well be shortening your life.
Employees who regularly put in 11- to 12-hour days have an almost 60 per cent greater risk of having a heart attack than those who put in a standard 7 to 8 hours daily, according to a study published in Wednesday's edition of the European Heart Journal.
"Our findings suggest a link between working long hours and increased coronary heart disease risk," said Dr. Marianna Virtanen, an epidemiologist at the Finnish Institute of Occupational Health in Helsinki and lead author of the study.
She said, however, that the overtime hours were not, in and of themselves, causing heart problems, but rather that they likely reflect the stress being felt by those who work long days.
The exact mechanism by which stress damages the heart is unknown, but it is widely speculated that excess physical and psychological demands cause unhealthy increases in blood pressure.
Gordon McInnes, a professor of clinical pharmacology at the University of Glasgow in Scotland, said the findings suggest that work habits (and demands placed on workers by employers) may have a much greater impact on health than previously recognized.
"Overtime-induced work stress might contribute to a substantial proportion of cardiovascular disease," he said in an editorial also published in the European Heart Journal.
Dr. McInnes suggested that, in addition to testing blood pressure and cholesterol levels, and verifying smoking history, physicians should be asking patients about their work hours as a means of judging their cardiovascular risk.
"Physicians should be aware of the risks of overtime and take seriously symptoms such as chest pain, monitor and treat recognized cardiovascular risk factors, particularly blood pressure, and advise an appropriate lifestyle modification," he said.
The findings are based on data from the Whitehall study, a long-running research project involving thousands of British civil servants.
This analysis involved 4262 men and 1,752 women aged 39 to 61 who worked full-time in London-based civil service departments. The employees were followed between 1991 and 2004.
During that period, 369 of the workers suffered heart attacks or developed angina. (Workers with pre-existing cardiovascular disease were excluded.)
Just more than half the participants, 54 per cent, said they typically did not work overtime; 21 per cent said they worked an extra hour a day on average; 15 per cent said it was two hours; and 10 per cent said they put in three or more hours daily of overtime.
In the later group, the risk of heart attack was 56 per cent greater than among those who did not work overtime. Among those who worked an extra two hours daily, the increased risk was 21 per cent. Those who put in an additional hour did not see their risk increase.
The increased risk was independent of other socio-demographic and lifestyle factors such as income and smoking, which bolsters the notion that overtime has an impact on heart health.
Dr. Virtanen noted that, because the study involved civil servants, one needs to be cautious about assuming that it applies to blue-collar workers or those who are self-employed.
In fact, she noted that one of the factors that mitigated the risk of heart attack, regardless of hours worked, was having control over one's work (and work hours), a key element that has arisen in Whitehall studies for decades.