long working hours

Long working hours may lead to less sleep and other health problems. A recent study investigated if long working hours were associated with the risk of heart disease or high blood pressure.

People who work long hours may be under increased stress, with less time for sleep, relaxing leisure-time activities, and exercise. Several studies have suggested that long working hours could harm health, increasing the risk of strokes or heart disease. However, other studies have not found evidence that working hours is related to illness.

It is possible that some of the beneficial effects of working longer, such as improved financial security, may counteract the negative effects. There might also be differences between countries. A recent Danish study investigated if working long hours was associated with an increased risk of high blood pressure and heart disease. The results were published in the scientific journal BMJ Open.

The Danish Labour Force Survey

Every year, the Danish government conducts a national survey to determine typical working hours within their country. The researchers obtained all the survey results from 1999 – 2013. They identified all the survey respondents between 21 – 59 years of age and who reported worked 32 to 100 hours per week. The researchers wanted to investigate how many developed high blood pressure or heart disease after the survey, so they excluded individuals who already had either illness at the time of the survey. After all this, they ended up with more than 125,000 adults in the study.

The researchers then consulted national medical records to identify all the surveyed employees who later developed heart disease or high blood pressure.

Long working hours were not associated with heart disease or high blood pressure

More than 80% of the employees reported working 32–40 hours a week. Only 6% reported working more than 48 hours. More than 3,500 people in the study developed heart disease after answering the survey. More than 20,000 developed high blood pressure. However, these diseases were not more common in people with long working hours.

The researchers also divided up the employees by socioeconomic status, by day and night work, and by gender. They found that none of these factors had any significant impact on the risk of developing heart disease or high blood pressure due to long working hours.

There was, however, a small trend towards increased heart disease among workers of low socioeconomic status who work very long hours. Unfortunately, there were so few people in this category that the researchers were not sure if these results were reliable.

Is Denmark typical of all countries?

This study included more than 100,000 individuals and is the largest study ever conducted on the relationship between working hours and heart disease. It relied on comprehensive national surveys and health registries, increasing the accuracy of the data. However, it is possible that Denmark is not representative of all countries. Most employees reported working 40 hours or less, and other countries may have social or economic factors that result in longer working hours.

The researchers also suggested that more research is needed on workers of low socioeconomic status who work very long hours. Despite this caveat, they found no significant evidence that longer working hours in Denmark resulted in heart disease or high blood pressure.

Written by Bryan Hughes, PhD

Reference: Hannerz, H., Larsen, A. D. & Garde, A. H. Long weekly working hours and ischaemic heart disease: a follow-up study among 145 861 randomly selected workers in Denmark. BMJ Open 8 (2018). http://bmjopen.bmj.com/content/8/6/e019807

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