London, Feb 15 (IANS): Hypertensive women with physically demanding jobs are at nearly three times higher risk of ischaemic heart disease, a condition that affects blood supply to the heart, warns a study.

The combination of hypertension (commonly known as high blood pressure) and high physical activity at work increased the risk of ischaemic heart disease more than adding the individual risks together, the study said.

"There is an additive interaction between hypertension and high physical activity at work. The two risk factors appear to work together, resulting in an even greater incidence of heart disease,” said lead author Karen Allesøe, research student at the University of Southern Denmark.

"It means hypertensive women with physically demanding work may be especially at risk of heart disease," she added.

Physically demanding work causes rise in heart rate and blood pressure, which can give way to plaques in the arteries and develop atherosclerosis, a disease in which plaque made up of fat, cholesterol builds up inside the arteries.

In the study, nurses with hypertension and high physical activity at work proved to be at a greater risk as both high physical activity at work and long periods of sitting increase the risk of heart disease, the findings, published in the European Journal of Preventive Cardiology, showed.

Nurses with normal blood pressure and high physical activity at work had a small increased risk of heart disease (about 20 percent) but this was not statistically significant after adjusting for traditional cardiovascular risk factors such as diabetes and smoking, the researchers explained.

During the 15-year follow up period, 580 nurses developed ischaemic heart disease, the researchers said.

Nearly 12 percent reported having hypertension. Physical activity at work was reported as high in 46.3 percent of the nurses, moderate in 34.4 percent and sedentary in 19.3 percent, the study revealed.

The study included 12,093 female nurses from the 1993 Danish Nurse Cohort Study. Data on hypertension and physical activity at work were collected using a questionnaire.

Physical activity at work was classified as sedentary, moderate (mainly standing and walking but not physically exerting), and high (standing or walking with some lifting or carrying; and heavy or fast and physically exerting).