According to the WHO, about 31% of all deaths worldwide (17.7 million deaths per year) [1] are attributable to cardiovascular disease (CVD), making CVDs the number 1 cause of death globally. Known risk factors for the development of CVD, among others, are smoking, high blood pressure or the lack of physical activity. Especially the latter has been discussed in the recent years and it became known that long hours of sitting [2] may increase your risk of CVD and diabetes (and may apparently even increase mortality, in the case of binge watching [3]). While numerous risk factors for CVD are known and several recommendations and guidelines on how to handle them exist, the prognostic role of what may possibly be one of the most common and important factors on cardiovascular health nowadays has not yet been formally assessed: stress at work.
New data
The team of the Individual-Participant-Data-(IPD)-Work Consortium now published a study in The Lancet Diabetes & Endocrinology [4] examining the effect of work-related stress on mortality in individuals with and without pre-existing risk factors (i.e. diabetes, coronary heart disease or history of stroke).
The researchers examined seven independent cohort studies, extracting information on work stress, mortality and conventional cardiovascular risk including smoking, drinking, alcohol consumption and BMI. Two indicators of common work stress were investigated: job strain (i.e. high demands in combination with low control) and effort-reward imbalance at work, both assessed using validated questionnaires.
The studies that had been conducted between 1985 and 2002 contained data of 105 284 participants of which 102 663 were eligible. At baseline, job strain was prevalent in 12.2% of men with prevalent cardiometabolic disease.
While in men without cardiometabolic disease, effort-reward imbalance-related work stress was mildly associated with an increased risk of mortality, in men with cardiometabolic disease, it was job strain that was associated with an increased risk of mortality (149.8 per 10 000 person-years vs. 97.7 per 10 000 person-years). For comparison, the risk of mortality for smokers was 164 per 10 000 person years (vs. 89.4 in non- and 83.5 in former smokers per 10 000 person years). In women, both with or without pre-existing cardiometabolic disease, no association with increased risk of mortality could be found.
Upon examination of death rates associated with job strain in men with cardiometabolic disease, it was found that the mortality difference in men with and without job strain was comparable to that of smokers and non-/former smokers (52.1 versus 78.1 in 10 000 person-years, respectively). The difference remained, whether or not subjects had high cholesterol, obesity, physical inactivity, high alcohol consumption or hypertension.
Lastly, even men with CVD but a favorable risk profile, e.g. non-obese, normal cholesterol and physical activity, had a two to six times higher risk of mortality if exposed to job strain.
Conclusion
This is the largest study of its kind showing that men with cardiovascular disease or diabetes are at an increased risk to die prematurely due to job strain. While most guidelines have clear recommendations [5] and even numerical ranges on risk factors such as blood lipids, blood pressure, obesity, smoking, drinking or physical inactivity, there are as of yet no clear guidelines on which levels of work stress are tolerable and when action should be taken (and if so, which?).
Although it remains unclear why job strain in particular contributes to increased mortality risk in men with cardiometabolic disease while effort-reward imbalance somewhat increases mortality risk in healthy men, this study may be the first step towards a paradigm shift on how we perceive, diagnose and cope with work stress.