Individuals working for longer hours at higher risk of stroke

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Working for longer hours not only gets in the way of your social life, it also ups your risk of suffering from a stroke, a new study has suggested.

Normal working hours for any individual falls in the range of 35 to 40 hours per week; however there are times when due to number of reasons people are required to put in extra hours of work either every few weeks or routinely.

A study, which is the largest field study of its kind and published in The Lancet, suggests that this is not what people should do as it working 55 hours or more per week increases an individual’s risk of stroke by 33 per cent. Further, it also ups the individual’s risk of suffering from a coronary heart disease by 13 per cent.

Researchers including Mika Kivimäki, Professor of Epidemiology at University College London, UK, carried out a systematic review and meta-analysis of published studies and unpublished individual-level data to examine a possible link between longer working hours and cardiovascular disease up to August 20, 2014.

The findings were startling. In an analysis of 25 studies involving over half a million people [603838 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 in people working 55 hours or more per week compared with those who put in normal 35 to 40 hour week. The risk remained at this level even after accounting for other risk factors including age, sex, and socioeconomic status.

In another analysis of data from 17 studies involving 528908 men and women researchers found a 1.3 times higher risk of stroke in individuals working 55 hours or more a week compared with those working standard hours.

There was no change in the association even after accounting for health behaviours such as smoking, alcohol consumption, and physical activity, and standard cardiovascular risk factors including high blood pressure and high cholesterol.

The gist of the findings is that more working hours an individual puts in, the higher the change of them suffering from 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.

Beyond the prolonged working hours, those who have had other high-risk behaviour are at even a higher risk of stroke, the study authors said.

Professor Kivimäki pegs their analysis as being more precise association between working hours and cardiovascular disease risk than any other previous such studies. The professor urges that health professionals should be aware that working long hours do significantly increased risk of stroke, and perhaps also coronary heart disease.

Longer working hours = Less sleep (sleep apnea) -> Increase risk of stroke

In a study, published earlier this year in June, researchers established a similar association between sleep disorders and risk of heart attack and stroke – an association which they say calls for addition of sleep as a risk factor to recommendations for preventing cardiovascular disease.

Researchers have long known that sleep disorders are very closely related to the cardiovascular diseases, but there has been no population based cohort study examining the impact of sleep disorders on the development of a heart attack or stroke.

The study included a representative sample of 657 men aged 25 to 64 years with no history of heart attack, stroke or diabetes in Novosibirsk, Russia. Researchers assessed sleep quality when the study began in 1994 using the Jenkins Sleep Scale. Very bad, bad or poor ratings were considered a sleeping disorder. Cases of myocardial infarction and stroke were recorded over the next 14 years.

During the study period, nearly two-thirds (63 per cent) of participants who had a heart attack also had a sleeping disorder. Sleeping disorders are closely associated with negative affective states (anxiety, depression, hostility, vital exhaustion). They are connected with the social gradient and are a manifestation of social stress in the population.

Men with a sleeping disorder had a risk of myocardial infarction that was 2 to 2.6 times higher and a stroke risk that was 1.5 to 4 times higher than those without a sleeping disorder between 5 and 14 years of follow up.

In yet another study published in June in journal Sleep, researchers from Karolinska Institute in Stockholm, Sweden have established a causal pathway that links job stress and sleep disturbances. Researchers found that higher work demands predicted subsequent sleep disturbances at the two-year follow-up. Similarly, sleep disturbances predicted a higher perception of stress, higher work demands, a lower degree of control, and less social support at work two years later.