Individuals with high-strain jobs are more likely to develop atrial fibrillation, which is a common heartbeat disorder that can significantly raise the risk of stroke.

People who have high-stress jobs — such as assembly line workers — may be more likely to develop A-fib.

This was the conclusion of a new Swedish study on work stress, now published in the European Journal of Preventive Cardiology.

The researchers define "high-strain jobs" as those that are "psychologically demanding" but give job-holders little control "over the work situation."

Examples include bus driving, nursing, and working on assembly lines.

Previous studies have linked work stress to coronary heart disease, but whether there is also a link to atrial fibrillation (A-fib) is less clear.

According to first study author Eleanor I. Fransson, who is an associate professor of epidemiology at Jönköping University in Sweden, A-fib "is a common condition with serious consequences and therefore it is of major public health importance to find ways of preventing it."

A-fib and consequences

A-fib affects millions of people in the United States. It occurs when the upper two chambers of the heart (the atria) beat abnormally and disrupt blood flow to the lower two chambers (the ventricles).

The condition, which can be temporary or permanent, raises the risk of stroke. A person with A-fib has a four to five times higher risk of having a stroke than a person without it.

A study found a 30 percent higher risk of A-fib among those scoring high on a clinical test for depression and taking antidepressants

As well as irregular heartbeat, individuals with A-fib might also experience: chest pain, palpitations (a fluttering or pounding sensation in the heart), shortness of breath, feeling lightheaded, and "extreme fatigue."

However, some people with A-fib may have no symptoms and not even realize that they have it.

Each year in the U.S., A-fib is responsible for over 750,000 hospital admissions and contributes to 130,000 deaths. Deaths in which A-fib is a contributory or primary cause have been increasing for the past 20 years.

The costs associated with A-fib are substantial. Overall, the burden in the U.S. amounts to $6 billion per year. The average annual medical bill for treating an individual with A-fib is $8,705 higher than for those without it.

Demands-control model

To assess work stress, Prof. Fransson and team used a measure of job strain that is based on the job demands-control model. It is one of the "most widely studied" models of work stress.

It is based on the idea that the effect of job demands on the strain that people experience is "buffered" by the amount of control that they have over their work.

For their study, the researchers used a Swedish questionnaire based on the model. It comprises five items on job demands and six on control.

The questions ask, for example, whether the individual:

•  has "to work very hard or very fast"

• experiences conflicting demands in the job

•  has enough time to complete tasks

•  has to complete lots of repetitive tasks

• is able to decide which tasks to do and how to do them

Link between job strain and A-fib

The researchers used data on 13,200 individuals who constituted a "representative sample of the working population" of Sweden. They were recruited in 2006, 2008, and 2010 to take part of the Swedish Longitudinal Occupational Survey of Health (SLOSH).

None of the participants had A-fib — or a history of the disorder — when they joined the study. Neither did they have a history of heart failure or heart attack.

They were all employed, and they all completed a battery of questionnaires when they entered the study. These were sent out by post and included the usual demographic questions plus others about health, lifestyle, and work.

The study followed the group for a median of 5.7 years. Using national registers, the researchers identified 145 cases of A-fib during this period.

Analysis of the SLOSH data — after adjusting for age, gender, and education — showed that job strain was linked to an almost 50 percent raised risk of A-fib.

The risk stayed the same when the team further adjusted the results to take into account the effect of exercise, smoking, blood pressure, and body mass index (BMI).

Pattern 'consistent' with other data

The researchers carried out a further analysis in which the SLOSH data were pooled with data from two other similar studies. This found that job strain was linked to a 37 percent higher risk of A-fib.

"Across studies," states Prof. Fransson, "there was a consistent pattern of work stress being a risk factor for atrial fibrillation."

She urges employees who feel stressed due to work and experience palpitations — or any other symptom of A-fib — to see their doctor and talk to their boss about improving their situation.

"Work stress should be considered a modifiable risk factor for preventing atrial fibrillation and coronary heart disease." - Prof. Eleonor I. Fransson