Recurrent CV Event Risk Hiked by Long Work Hours
—Findings from a prospective cohort study indicate that reducing work hours—from 55 or more a week to between 35 and 40—may be a preventive strategy for patients with a history of heart attack.
Researchers in Canada have identified a potentially new pathway to preventing subsequent cardiovascular events: working fewer hours.
Among patients who return to work after a myocardial infarction (MI), those who work 55 or more hours per week increase their overall odds of having a second MI by 67% compared with those working an average full-time job of 35 to 40 hours a week, according to a prospective cohort study conducted by researchers at Laval University, in Quebec City.1
“Long working hours and psychosocial stressors at work are precise and modifiable factors,” Xavier Trudel, PhD, researcher at the CHU de Quebec-Laval University Research Center and corresponding author of the study, told ڴŮ. “Their adverse effect on cardiovascular health was consistently shown in a large number of high-quality prospective studies. Their prevalence in the working population is comparable to that of well-known lifestyle risk factors, including smoking, physical inactivity, and heavy drinking. Therefore, there’s a need for an increased recognition of these work-related factors in clinical practice.”
The study was published in the Journal of the American College of Cardiology and is the first of its kind to examine working hours as a risk factor for recurrent coronary heart disease (CHD) events.
Tracking rates of coronary events by working hours
The prospective cohort study included 967 participants (864 men and 103 women between the ages of 35 and 59) from 30 hospitals across the Canadian province of Quebec, between November 1995 and October 1997.1 Eligibility requirements included having had a previous initial acute MI, being younger than 60 years old, having paid employment within a year of an MI, and plans to go back to work for at least 10 hours a week within 18 months of an MI.
During follow-up telephone interviews (mean follow-up, 5.9 years), researchers discovered that 205 (21.2%) patients experienced recurrent CHD events, with those working long hours having the highest rate of recurrence.
Here are the rates per 100 person-years of recurrent coronary events by weekly working hours:
- Part time (21 to 34 hours): 2.77
- Full time (35 to 40 hours): 3.48
- Low overtime (41 to 54 hours): 3.27
- Medium/high overtime (≥55 hours): 7.07
In the unadjusted analysis, participants who said they worked ≥55 hours a week had a twofold increase (hazard ratio [HR] 2.00, 95% confidence interval [CI] 1.36 to 2.95) in recurrent CHD risk compared with those working a typical full-time workweek (35 to 40 hours). In the fully adjusted model, which controlled for sociodemographics, lifestyle habits, clinical risk factors, work environment, and personality factors, participants working long hours still bore a higher risk of recurrent CHD compared with those working 35 to 40 hours a week (HR 1.67, 95% CI 1.10 to 2.53).
Workaholic tendencies are as bad as smoking
“This risk is further increased when long working hours are combined with psychosocial stressors at work and after the first 4 years of follow-up,” says Alain Milot, MD, co-author of the study.
But the most surprising finding, Dr. Trudel says, was how higher numbers of working hours compared to one of the most well-known cardiovascular risk factors.
“The increased risk associated with long working hours was comparable to that of current smoking: 67% and 70%, respectively,” he says. “And when long working hours are combined with work stressors, the risk is higher than the one posed by smoking.”
Long work hours increase other risk factors
The authors noted that study participants who worked ≥55 hours per week also reported more traditional coronary disease risk factors, such as smoking, alcohol use, sedentary lifestyle, and high levels of stress.
According to Dr. Trudel, overworked individuals increase their risk of recurrent cardiovascular events through different mechanisms, including prolonged exposure to work stressors, sleep deprivation, and changes in lifestyle habits.
Those who work longer hours are also at higher risk of increased blood pressure (BP), as demonstrated by a 2020 study conducted by several of the current study’s authors, where long working hours were an independent risk factor for masked and sustained hypertension.2 Masked hypertension, Dr. Trudel explains, is defined by high ambulatory BP and normal clinic BP, while sustained hypertension is defined by high BP according to both types of BP measurements. Moreover, both types of hypertension are associated with an increased cardiovascular risk.
Work-life balance as preventive medicine
Nearly 18 million people worldwide die each year from cardiovascular disease, making it the leading global cause of death.3 Identifying new ways to prevent it remains a challenge for researchers and clinicians alike. This study offers a new talking point for clinicians in follow-up discussions with patients: how work behaviors contribute to heart health.
As such, Dr. Trudel says clinicians, during routine clinical follow-ups, should ask any patient who intends to return to their job post-MI about their work habits and work stressors.
Patients can do their part as well, Dr. Trudel suggests. “Since long working hours were linked with masked hypertension, performing an ambulatory blood pressure monitoring or self-measuring blood pressure at work may improve the screening for masked hypertension among patients working long hours,” he says.
Finally, even though the current study concluded that working long hours after a first MI is comparable to the burden of being an active smoker, Dr. Milot says further studies are needed to clarify the causal pathways linking long working hours and recurrent coronary events.
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