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30-09-2010 | Cardiology | Article

Low physical fitness doubles IHD risk from long working hours in men

Abstract

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MedWire News: Working for more than 45 hours per week increases men's risk for ischemic heart disease (IHD)-related mortality only if they have low physical fitness, Danish researchers report.

"The cardiovascular (CV) health impairment attributed to long work hours is generally considered to be caused by a prolonged elevated heart rate and blood pressure when working long hours compared to normal working hours, irrespective of the work being physically demanding or not," explain Andreas Holterman from the National Research Center for Working Environment in Copenhagen, Denmark, and colleagues.

However, they note that "physically fit people have a lower relative CV stress during a specific task and improved recovery from physical exertion compared to persons with low physical fitness."

To determine if this influences the effect of working hours on CV risk, Holterman and team assessed the working hours and physical fitness of 4943 employed men aged 40 to 59 years.

All participants reported their working hours by questionnaire and physical fitness was determined by estimating maximal oxygen consumption (VO2max) during bicycle ergometer test. Low (n=892), intermediate (n=3037), and high levels of physical fitness (n=1014) were defined as VO2max range 15-26, 27-38, and 39-78, respectively.

Over a follow-up period of 30 years, 2663 (54.0%) men died, 587 of these from IHD.

As reported in the journal Heart, after adjustment for social class, age, and other confounding factors, Holterman and team found that the men with low physical fitness who worked more than 45 hours per week had a 2.28-fold increase in IHD mortality risk compared with those with low fitness who worked less than 40 hours per week (p<0.05).

Among the men with intermediate or high physical fitness, no significant difference in IHD mortality risk was found when those working more than 45 hours were compared with those working less than 40 hours per week.

Holterman and team conclude: "This finding strengthens the present documentation of adverse health effects from long work hours, and supports that the lack of work time directives in some countries (eg, USA) may be a public health problem."

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Lauretta Ihonor

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