A report suggests the phrase “working overtime is killing me” may be as factual as it is figurative. According to a long-term study of more than 10,000 civil servants in London, working overtime is bad for the heart.


The research, published online in the European Heart Journal, found compared with people who did not work overtime, those who worked three or more hours longer than a normal, seven-hour day had a 60 percent higher risk of heart-related problems such as death due to heart disease, nonfatal heart attacks and angina.


Dr. Marianna Virtanen, an epidemiologist at the Finnish Institute of Occupational Health, Helsinki (Finland) and University College London (UK), said: “The association between long hours and coronary heart disease was independent of a range of risk factors that we measured at the start of the study, such as smoking, being overweight, or having high cholesterol.


“Our findings suggest a link between working long hours and increased CHD (coronary heart disease) risk, but more research is needed before we can be confident that overtime work would cause CHD. In addition, we need more research on other health outcomes, such as depression and type 2 diabetes.”


The study launched in 1985 and recruited 10,308 office staff between the ages of 35 and 55 from 20 London-based civil service departments. Data was collected at regular intervals and in the third phase, between 1991-1994.


This current analysis looks at the results from 6,014 people (4,262 men and 1,752 women), ages 39 through 61, who were followed until 2002-2004, which is the most recent phase for which clinical examination data are available.


During the average 11.2 years of follow-up, Dr. Virtanen and her colleagues in Finland, London and France found that there had been 369 cases of fatal CHD, nonfatal heart attacks (myocardial infarctions) or angina.


After adjusting for significant factors such as age, sex, marital status and occupational grade, they found that working three to four hours overtime (but not one to two hours) was associated with a 60 percent higher rate of CHD compared with no overtime work. Additional adjustments for a total of 21 risk factors made little difference to these estimates.


The researchers say there could be a number of possible explanations for this association between overtime and heart disease.


Their results showed that working overtime was related to type A behavior pattern. People with type A behavior tend to be aggressive, competitive, tense, time-conscious and generally hostile. Psychological distress usually expressed as anxiety and depression, insufficient sleep, or relaxation time prior to sleep may have been factors.


Other potential causes include hypertension (high blood pressure) associated with  associated with work-related stress but is “hidden” because it isn’t usually present during medical exams and “sickness presenteeism” whereby employees who work overtime are more likely to work while ill, ignore symptoms of ill health and not seek medical help.


It’s possible that people in jobs where they have more freedom regarding their work-related decisions may have a lower risk of CHD despite working overtime.


However, Dr. Virtanen said that their findings were independent of all of the above factors, and so they could not necessarily provide the full explanation for why overtime was associated with the higher risk of heart disease.


In addition, she said: “We did not measure whether subsequent changes in these factors during the follow-up period altered the association. One plausible explanation for the increased risk could be that adverse lifestyle or risk factor changes are more common among those who work excessive hours compared with those working normal hours.


The authors also warn in their article: “Although our cohort of civil servants included several occupational grades, it did not include blue collar workers. Thus, it remains unclear whether our findings are true of blue-collar workers and employees in the private sector.”


Regarding future research, Mika Kivimäki, the study’s senior author and professor of social epidemiology at University College London remarked: “At the moment there is no research on whether reduction in overtime work reduces CHD risk. Further research on this topic is therefore needed,” he said.


“Our own future research will include analyzing data over periods of time to examine whether working long hours predicts changes in lifestyle, mental health and traditional risk factors, such as blood pressure, blood glucose and cholesterol. We hope that this research will increase understanding of the mechanisms underlying the association between long working hours and coronary heart disease. We will also examine whether overtime work increases the risk of depression, as recent research suggests that depression increases the risk of coronary heart disease.”


Source:  http://www.escardio.org/Pages/index.aspx