Job strain poses heart risk

People who face high demand in their jobs but have little control are significantly more likely to experience a coronary event than other workers, shows a large meta-analysis published online in The Lancet.

"Our findings indicate that job strain is associated with a small, but consistent, increased risk of experiencing a first CHD [coronary heart disease] event such as a heart attack," said Mika Kivimäki (University College London, UK) in a press release.

The study used individual records from 197,473 participants without heart disease, from 13 European national cohorts. Importantly, the authors included both published and unpublished data.

Participants completed questionnaires which showed that job strain - a combination of work demand and control - was experienced by 15%. Participants were aged 42 years on average at entry to the study and were followed-up for a median of 7.5 years. There were 2358 events of incident CHD (first non-fatal heart attack or coronary death).

The authors found that, when they adjusted their analyzes for age and gender, participants with job strain had a 23% increased risk of a CHD event compared with those without.

Adjusting for other known risk factors such as body mass index, physical activity levels, and smoking did not significantly alter the association between job strain and CHD events.

The authors calculated that job strain is responsible for a 3.4% population-attributable risk (PAR), indicating that targeting job strain could reduce disease incidence. However, they highlight that this PAR is much lower than for other risk factors such as smoking (36%), abdominal obesity (20%), and physical inactivity (12%).

However, in a linked comment Bo Netterstrøm (Bispebjerg Hospital, Copenhagen, Denmark) says: "Job strain is a measure of only part of a psychosocially damaging work environment, which implies that prevention of workplace stress could reduce incidence of CHD to a greater extent than stated in the authors' interpretation of the calculated PAR for job strain."

While the association between work stress and CHD has already been documented, the authors say that their design helps to overcome previous methodologic flaws that have plagued earlier analyzes.

For example, to minimize reverse causation they excluded cases of CHD within the first 3 and 5 years of follow-up and found that the association between work strain and CHD events increased.

Furthermore, they found that unpublished data showed significantly weaker associations than those that were published, confirming that this area of research is subject to publication bias.

"The pooling of published and unpublished studies allowed us to investigate the association between CHD and exposure to job strain with greater precision that has been previously possible," said Kivimaki.

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