Long working hours tied to stroke risk

People who work at least 55 hours a week are significantly more likely to eventually suffer a stroke than people who work 35 to 40 hours a week, a recent study suggests.

Previously, the same research team had linked longer working hours with an increased risk of type 2 diabetes, but only for those in lower socioeconomic groups.

“This was not the case for stroke: the association between long working hours and stroke was similar” at all socioeconomic levels, said lead author Mika Kivimaki of University College London, in an email.

The researchers pooled the data from 25 studies in Europe, the U.S. and Australia that tracked more than 600,000 workers for seven to eight years on average. Participants had no history of stroke or coronary heart disease when they enrolled in the studies.

Over time, they had 4,768 heart attacks or heart disease events and 1,722 strokes.

As working hours got longer, stoke risk increased, the researchers found. Working at least 55 hours per week increased stroke risk by 33 percent compared to working a standard full-time job 40 hours per week, even when age, sex and socioeconomic status were accounted for.

In real terms, however, stroke is rare in working populations, Kivimaki point out. In this analysis, there were 4.5 strokes per 1,000 employees – and among those working long hours, the rate rose to 6 strokes per 1,000 employees.

There was also an increase in heart disease risk, but the association was weaker and the risk was smaller, the authors wrote in The Lancet.

“Coronary heart disease and stroke share several risk factors,” but some, like cardiac arrhythmia, are more strongly related to stroke, Kivimaki said.

Jobs requiring long working hours can range from low to high-paying, he said.

“Stroke is a multifactorial disease and therefore a person's risk of stroke is almost always the result of multiple interacting risk factors,” Kivimaki said.

Keeping blood pressure, lipid levels and blood glucose within the normal range, getting enough exercise, eating and drinking healthfully, avoiding excess weight and excessive stress can all reduce stroke risk, he said.

“Even if an increased risk of 30 percent is rather low for an individual, people should think of it,” said Urban Janlert of Umea University in Sweden, who wrote an editorial about the new results.

“But the main problem is the public health aspect – even if the individual risk is not alarming, the high number of people working long hours means that in the whole population a huge number of strokes will occur,” Janlert told Reuters Health by email.

If you have long working hours, recovery periods are important, he said. Working long hours for two to three weeks is likely more harmful than shorter periods.

“I hope that people become aware that long working hours are associated with an increased risk of stroke,” Kivimaki said. “Those who work long hours should be extra careful that they still maintain a healthy lifestyle and ensure their blood pressure and lipid levels are within the normal range.”