Stressed out at work? Men face elevated risk of heart disease

In a recent study published in Circulation: Cardiovascular Quality and Outcomes, researchers investigated how job strain and effort-reward imbalance (ERI) interact to increase the risk of developing coronary heart disease (CHD). They found that men who experienced either job strain or ERI had significantly higher chances of having CHD, with the risk more than doubled for men who experienced both.

Background

Non-communicable diseases account for nearly three-quarters of global deaths. Cardiovascular diseases comprise the largest part of these cases, and CHD has now emerged as the most common cardiovascular disease, causing 9 million deaths yearly. Researchers have identified various biological, social, and lifestyle risk factors, which, if targeted, could reduce the global burden of CHD.

Work-related stresses are known to increase the risk of CHD. Under the job strain model developed by Robert Karasek, those working in psychologically demanding jobs with lower control or autonomy are more stressed than those working in equally demanding jobs with higher control or autonomy. In this context, a worker who has a less demanding job and more autonomy experiences the least stress. At the same time, ERI arises when the effort made by the worker is not adequately compensated and is also known to affect health. Rewards need not be purely monetary – they could also relate to job stability or opportunities for promotion.

Scientists have established how job strain and ERI individually increase CHD risks. Workers who experience both these negative working conditions could be especially affected, but this has not been sufficiently explored. In the present study, a team of researchers from Canada and the UK aimed to understand how combined exposure to ERI and job strain can affect CHD risk.

"The combined effect of job-strain and effort-reward imbalance may be especially harmful; however, evidence of their combined effect on coronary heart disease incidence is limited and inconsistent."

About the study

In this study, researchers included 6,465 workers, of whom 3,118 were male and 3,347 were female. The workers were in their mid-forties, all had white-collar jobs, and were healthy (i.e., did not have any heart disease); they were part of the PROspective Québec (PROQ) cohort data collected between 1999 and 2001. Since this was a prospective cohort study, the participants were followed up for nearly 19 years, with data on their cardiovascular health and work stress collected until 2018.

Workers were asked to fill up a Job Content Questionnaire and were sorted into four categories based on the psychological demands of and control over their work: (1) job strain with high demands and low control, (2) passive jobs with low demands and low control, (3) active jobs with high demands and high control, and (4) low job strain with low demands and high control. The workers were also asked detailed questions regarding the effort they put into their jobs and the rewards they received, and this information was used to calculate the ERI ratio.

The researchers then assessed each participant's exposure to job strain and ERI, with the least exposed (or 'unexposed') being those with low job strain but not low rewards, while the most exposed experienced both job strain and an imbalance between effort and reward.

Finally, the researchers collected information about the participants' CHD events, their health-related behavior (such as smoking and drinking), lifestyle, and medical histories from various medical and administrative databases.

Using this dataset, the team constructed hazard ratios (HR), which can be interpreted as an estimate of the risk of CHD relative to the exposure to job strain and ERI. Researchers calculated the increase in CHD risk for each exposure category compared to those who were 'unexposed.'

Results

Overall, researchers found that about half of the men and women had low exposure to work stresses, while 22% were exposed to either ERI or job strain, but not both. Slightly over 10% of women and 8% of men were exposed to both categories, with the remaining individuals being classified as 'unexposed.' Researchers also noted that men were more affected by diseases such as diabetes and hypertension than women.

A total of 571 men and 265 women had a CHD event during the study. Men exposed to ERI or job strain, but not both, experienced a 49% increase in CHD, showing an HR of 1.49. However, among men exposed to both, the risk of CHD more than doubled, with an HR of 2.03. In stark contrast to the findings on men, the results for women were inconclusive, with higher exposure not being significantly associated with a higher CHD risk.

Conclusions

The researchers found compelling evidence that male workers exposed to job strain and ERI were at significantly higher risk of having a CHD event. This increase is comparable to that associated with another major risk factor – obesity.

The authors stressed that their findings do not mean that job strain and ERI do not increase the chances of CHD in women, although the results were inconclusive. Some of the reasons why there was no increase in the HR for female workers could be because they, as a population, experienced fewer CHD cases.

Women may also develop CHD later in life – the study may have missed these 'delayed-onset' cases because they happened after the follow-up period. Finally, some scientists think that estrogens could provide women with some degree of protection against CHD.

The authors noted, "In this prospective cohort study, men exposed to job strain or ERI, separately and in combination, were at increased risk of CHD. Early interventions on these psychosocial stressors at work in men may be effective prevention strategies to reduce CHD burden."

Further investigation into the relationship between work stress and CHD in women could yield interesting insights. In the meantime, reducing work-related stresses will benefit not just men but all workers.

Written by

Susha Cheriyedath

Susha has a Bachelor of Science (B.Sc.) degree in Chemistry and Master of Science (M.Sc) degree in Biochemistry from the University of Calicut, India. She always had a keen interest in medical and health science. As part of her masters degree, she specialized in Biochemistry, with an emphasis on Microbiology, Physiology, Biotechnology, and Nutrition. In her spare time, she loves to cook up a storm in the kitchen with her super-messy baking experiments.