Working 55 hours or more per week is linked to a 33 per cent
greater risk of stroke and a more modest (13 per cent) increased
risk of developing coronary heart disease compared with working a
standard 35 to 40 hour week, according to the largest study in this
field so far, led by UCL.
Professor Mika Kivimäki (UCL Epidemiology & Public Health)
and colleagues did a systematic review and meta-analysis of
published studies and unpublished individual-level data examining
the effects of longer working hours on cardiovascular disease up to
August 20, 2014.
Analysis of data from 25 studies involving 603,838 men and women
from Europe, the USA, and Australia who were followed for an
average of 8.5 years, found a 13 per cent increased risk of
incident coronary heart disease (a new diagnosis, hospitalisation,
or death) in people working 55 hours or more per week compared with
those putting in a normal 35 to 40 hour week, even after taking
into account risk factors including age, sex, and socioeconomic
status.
Analysis of data from 17 studies involving 528,908 men and women
who were followed up for an average of 7.2 years, found a 1.3 times
higher risk of stroke in individuals working 55 hours or more a
week compared with those working standard hours. This association
remained even after taking into account health behaviours such as
smoking, alcohol consumption, and physical activity, and standard
cardiovascular risk factors including high blood pressure and high
cholesterol.
Importantly, the researchers found that the longer people
worked, the higher their chances of a stroke. For example, compared
with people who worked standard hours, those working between 41 and
48 hours had a 10 per cent higher risk of stroke, and those working
49 to 54 hours had a 27 per cent increased risk of stroke.
Although the causal mechanisms of these relationships need to be
better understood, the authors suggest that increasing health-risk
behaviours, such as physical inactivity and high alcohol
consumption, as well as repetitive triggering of the stress
response, might increase the risk of stroke.
According to Professor Kivimäki, "The pooling of all available
studies on this topic allowed us to investigate the association
between working hours and cardiovascular disease risk with greater
precision than has previously been possible. Health professionals
should be aware that working long hours is associated with a
significantly increased risk of stroke, and perhaps also coronary
heart disease."
The paper, Long working hours and risk of coronary heart disease and stroke: a
systematic review and meta-analysis of published and unpublished
data for 603?838 individuals, is published
in The Lancet.