Working Long Hours Linked to Heart Disease Risk

April 5, 2011 -- People who work 11 hours or more on a daily basis may be at increased risk of developing coronary heart disease, a British study indicates.

The researchers note that doctors often use information from the Framingham Risk Score, which identifies common factors of heart disease, to predict a patient’s 10-year risk of developing coronary heart disease.

This score includes risk factors such as age, sex, cholesterol levels, blood pressure, and smoking habits, but not psychosocial factors such as daily work hours.

Scientists at University College London studied data on 7,095 civil service workers between the ages of 39 and 62, who at the beginning of the research project in 1991-92 showed no signs of coronary heart disease after a medical examination.

The participants were screened for coronary heart disease every five years until 2004. The researchers found that adding information about the participants’ work habits to standard data used in the Framingham risk score modestly improved prediction of people who would develop coronary heart disease.

According to the researchers, adults who said they worked 11 hours a day or longer had a 67% higher risk for developing coronary heart disease than people putting in seven or eight hours a day.

After a median of 12.3 years, 192 of the participants had been diagnosed with coronary heart disease.

Tracking Heart Risk

The study was based on data from the British Whitehall II study, an examination of British civil servants that was established in 1985 to identify characteristics of a working environment and health-related risk behaviors.

Participants, more likely to be men and younger, were between 49 and 53.6 years of age. They filled out questionnaires to record working hours.

According to the study:

• 54% of the participants worked seven to eight hours a day.
• 10.4% worked 11 hours or more.

The researchers say they were able to demonstrate that long working hours, when added to Framingham risk scores, better predicted coronary heart disease and death.

Because long working hours are common, the study has important implications, according to the researchers. They say incorporating information on working data in their assessments of patients may help doctors do a better job of evaluating people with coronary heart disease.

The study is published in the Annals of Internal Medicine.