As the authors concluded, “Our findings show that individuals who work 55 hours or more per week have a 1.3 times higher risk of incident stroke than those working standard hours. Long working hours were also associated with incident coronary heart disease, but this association was weaker than that for stroke.”
The authors explained that the meta-analysis of 25 previous studies tracked 603,838 people. The study adjusted for self-reported factors, including smoking, alcohol consumption, body mass index and other factors.
The people who were working longer hours had higher rates of strokes when the researchers crunched the numbers, they said. Additionally, the researchers discovered that people who were from lower socioeconomic groupings also were likely to have more strokes and to develop coronary heart disease. They added that the risk of the latter was only increased by 13 percent.
There were 44 scientists who were listed as authors on the paper. Together, they hypothesized that physical inactivity, a tendency toward heavier alcohol consumption and even just a proclivity to ignore healthy symptoms while sitting at the desk could be a partially explain the linkage. However, they found that the very pressure of being at work could be the main underlying cause. As they concluded, “Sudden death from overwork is often caused by stroke and is believed to result from a repetitive triggering of the stress response.”
According to Mika Kivimaki, the lead author, from University College London, “The pooling of all available studies on this topic allowed us to investigate the association between working hours and cardiovascular disease risk with greater precision than has previously been possible.” The study is the “strongest indication of a causal association” yet for cardiovascular consequences of working too much, according to an accompanying Lancet analysis published by Urban Janlert, an epidemiologist from Umea University in Sweden.
Janlert wrote, “Long working hours are not a negligible occurrence. Therefore, that the length of a working day is an important determinant mainly for stroke, but perhaps also for coronary heart disease, is an important finding. For now, we have a risk factor that could and should be the subject of general policy decisions.”