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 For the study, researchers followed more than 85,000 working men and
women without an atrial fibrillation diagnosis for a decade,
starting when they were typically around 43 years old. During the
study period, people who worked at least 55 hours a week were 40
percent more likely to develop atrial fibrillation than those who
worked 35 to 40 hours.
“This study is important because it suggests a potential mechanism
that could link long working hours to stroke,” said lead study
author Dr. Mika Kivimaki of University College London in the UK.
To assess the connection between work hours and atrial fibrillation,
Kivimaki and colleagues examined data on workers in the UK, Denmark,
Sweden and Finland.
When participants joined the study between 1991 and 2004, about 63
percent of them worked a standard 35 to 40 hour workweek, while just
5.2 percent worked 55 hours or more.
Long working hours were associated with slightly higher rates of
obesity, inactivity, smoking and alcohol use.
During the study, 1,061 people were diagnosed with atrial
fibrillation, researchers report in the European Heart Journal. Only
10 percent of them had already been diagnosed with heart disease by
the time atrial fibrillation was found.
“For me, this was perhaps the most surprising finding,” Kivimaki
said by email. “Initially, I thought people who work long hours may
have a greater risk of coronary heart disease, which then elevates
atrial fibrillation risk. Our findings show that the association
from long working hours with atrial fibrillation was more direct.”
In atrial fibrillation, electrical impulses in the upper chambers of
the heart are chaotic, causing that part of the heart muscle to
quiver rather than contracting normally. As a result, blood doesn’t
move as well to the heart’s lower chambers. This can lead to the
formation of blood clots, which can then travel through the arteries
to the brain and cause a stroke.
Among people working a standard week, 12.4 out of every 1,000
developed atrial fibrillation, the study found.
But when people worked at least 55 hours, 17.6 out of every 1,000
got this diagnosis.
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The study wasn’t a controlled experiment designed to prove that
working too much directly causes atrial fibrillation.
Other limitations include the lack of data on the type of job people
worked or whether they typically worked day or night shifts, the
authors note. In addition, researchers only had data on work hours
and lifestyle behaviors like diet, exercise, smoking and alcohol use
from a single assessment done at the start of the study period.
People might have changed jobs, working hours or shifts during the
study, Drs. Lucas Boersma and Bakhtawar Mahmoodi, of St. Antonius
Hospital in Nieuwegein, The Netherlands, write in an accompanying
editorial. Shifts in things like diet and exercise might also
explain some of the connection between long work hours and atrial
fibrillation.
“It is probably not the direct effect of working longer hours that
causes atrial fibrillation to develop. Most likely it is in the
balance of amount of work load and how much work load each
individual is able to endure over the long term,” Boersma told
Reuters Health by email.
“The type of work is also of great importance: stress level,
physical labor, education and being equipped for the task at hand,
working changing shifts, traveling through different time zones
continuously, etc.,” Boersma added. “All of these may demand more
than individual systems can take.”
SOURCE: http://bit.ly/2vjEZVd and http://bit.ly/2vjAvyz European
Heart Journal, online July 14, 2017.
[© 2017 Thomson Reuters. All rights
reserved.] Copyright 2017 Reuters. All rights reserved. This material may not be published,
broadcast, rewritten or redistributed.
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