Workers Health & Safety Centre

New review shows long working hours raise risk of stroke

More attention needs to be paid to the vascular health of those working more than a 40 hour work week, a new European study suggests.
British researchers analyzed data from studies on more than 603,000 men and women from Europe, the U.S. and Australia who were followed for about eight years. They looked at the effects of longer work hours on cardiovascular disease. Researchers also analyzed data for over 525,000 men and women for the effects of longer work hours on stroke. These workers were followed for approximately seven years.
Those individuals who worked 55 or more hours a week showed about 1.33 times or 33 per cent higher risk of stroke compared with those who worked 35 to 40 hours a week, according to Mika Kivimaki, professor of epidemiology at University College London and his co-authors, in the online issue of the journal, The Lancet.
There was a weaker association—about 10 per cent, between long working hours and coronary heart disease, such as heart attacks and cardiac deaths.
The associations did not vary between men and women, by age, socioeconomic status or by geographical region which Kivimaki said, suggests the findings were “robust.”
During the study period there were 1,722 strokes. No one knows how working long hours adds to stroke risk. Kivimaki suggests the following possibilities:
  • A toxic effect from stress itself;
  • Extensive sitting and sedentariness on the job; or
  • Failure to follow a healthy diet and exercise routine outside of work.

Long working hours have long been implicated as a cause of cardiovascular disease. In two previous meta-analyses of published cohort studies, the risk of coronary disease was raised in employees working long hours compared to those working standard hours. The relative risk was about 1.4, which is considerable, because long working hours are common. However, there were several limitations in these previous studies which could have biased the estimates.
The authors of this new review conducted their study using methods that would overcome the limitations. One way they accomplished this was by combining estimates from published studies and unpublished data which allowed them to examine the status of long working hours as a risk factor for coronary heart disease and stroke with greater precision and a more comprehensive evidence base than was previously possible.
Want to read the review Long working hours and risk of coronary heart disease and stroke?
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