A demanding job increases the risk of premature death in men with heart disease or diabetes, a major review of cohort studies involving more than 100,000 people has found.

The findings of the multi-cohort review – drawing on data from seven cohort studies tracking 100,000 men and women in Finland, France, Sweden and the United Kingdom – was published today in The Lancet Diabetes & Endocrinology journal.

The study found no association between any type of work stress and premature death for women with or without the prevalent cardiometabolic diseases of coronary heart disease, stroke, or diabetes. Men without cardiometabolic disease had a slightly heightened risk of death associated with work that demanded a lot of effort for little reward.

A press release from The lancet said while some existing treatment already recommend stress management for people with cardiometabolic disease this study is the first large-scale study to investigate the link.

“Work is a common source of stress in adulthood, triggering natural stress responses that were programmed in our bodies generations ago,” says study lead Professor Mika Kivimäki, of University College London. “These can result in physical reactions to situations like work stress, and our findings give evidence for there being a link between job strain and risk of premature death in men with cardiometabolic diseases, such as coronary heart disease, stroke, and diabetes,”

He said the findings suggest that controlling blood pressure and cholesterol levels alone are unlikely to eliminate the excess risk associated with job strain in men with cardiometabolic disease. “Other interventions might be needed at least for some patients – possibly including stress management as part of cardiovascular disease rehabilitation, job redesign, or reducing working hours. However, more research will be needed to identify which specific interventions might improve health outcomes in men with coronary heart disease, stroke, or diabetes.”

The study included two types of work stress; job strain (having high work demands and low control over them) and effort-reward imbalance (putting in lots of effort, but getting little reward in return).

After controlling for socioeconomic status and several conventional and lifestyle risk factors (including high blood pressure, high cholesterol, smoking, obesity, physical inactivity, and high alcohol consumption), the authors found that, among men with cardiometabolic disease, those experiencing job strain had a 68% greater risk of premature death than men who had no job strain.

In addition, this increased risk was even present in men with cardiometabolic disease who had achieved their treatment targets, including those with a healthy lifestyle (including not being obese, being physically active, not smoking, and not drinking heavily), blood pressure, and cholesterol levels.

There was no association between risk of premature death and effort-reward imbalance in men with cardiometabolic disease, but men without cardiometabolic disease had a slightly heightened risk associated with this type of work stress.

Neither type of work stress was associated with increased mortality risk for women with or without cardiometabolic disease.

The authors say that job stress may affect the body in a number of ways to cause this association, including hijacking natural responses to stress, through heightened levels of the stress hormone cortisol, which increases glucose production and limits the effect of insulin, potentially leading to worse prognosis in diabetes. In addition, increased inflammation and increased activation of the ‘fight-or-flight’ response can elevate blood pressure and affect blood clotting, potentially increasing the risk of cardiac events in individuals who already have high levels of hardening of the arteries.

The authors noteD some limitations, including that the study only measured cardiometabolic disease and work stress at the start of the study, meaning it does not account for severity of disease or how it changes over time. The study did not control for blood pressure or cholesterol levels in all cohorts due to missing data, and this could lead to a small overestimation of the effect of job strain.

Equally, the authors note that people with more severe cardiometabolic disease tend to shorten their working hours, and this reduced effort may explain why there is no association between effort-reward imbalance and risk of premature mortality in men with cardiometabolic disease.

Writing in a linked Comment, Yulong Lian, Nantong University, China, says: “Although the authors argue that the difference in findings between the models might be related to different sources of stress and reduced effort in people with severe illness, other important prognostic factors associated with cardiometabolic disease might have biased these findings. The prevalence of poor mental health, such as psychological distress, clinical depression, and anxiety, is higher among patients with cardiometabolic disease than in the general population.

“Furthermore, compared with people with no stress, those with work stress tend to have a higher prevalence of poor mental health… Nevertheless, their results are provocative and encourage careful attention to work stress reduction among patients with cardiometabolic diseases…

“Further research into the mechanisms responsible for the these differences in the effects of work stress would not only improve understanding of the prognosis of cardiometabolic disease, but also inform health policy makers and guideline committees about the need for sex-specific workplace interventions for the treatment and management of cardiometabolic disease.”

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