LONDON: Blood pressure levels in the general population fell on average in 21 countries between the 1980s and 1990s but the drop was not due to medicines, researchers said on Friday.

Scientists who worked on the World Health Organisation MONICA study are not sure what caused the small but significant decline but they believe it could be due to a variety of factors, such as eating less salt and more fruit and vegetables.

High blood pressure is a leading risk factor for cardiovascular disease, which killed 16.7 million people worldwide and accounted for 29.2 per cent of global deaths, according to the World Health Report 2003.

“Blood pressure is changing in the population independent of medication,” said Professor Hugh Tunstall-Pedoe, of the Ninewells Hospital and Medical School in Dundee, Scotland.

“Whatever is moving, the blood pressure must be more powerful than medication,” he told Reuters.

Tunstall-Pedoe and his colleagues ruled out blood pressure lowering drugs because the decreases they saw in the study were not just in people with high blood pressure taking drugs to control it. Levels also decreased in people with middle and low readings.

“Blood pressure has got more dimensions than popping pills and people need to be aware of that,” he added.

But the researchers said medication is important for people suffering from high blood pressure.

Blood pressure is calculated by two measures. Systolic pressure, the top number on blood pressure readings, is the force in the arteries when the heart beats. Diastolic pressure, the bottom number, is the pressure when the heart is at rest.

A reading of around 120/75 mmHG (millimetres of mercury) is considered normal.

Although high blood pressure can occur in children, it is more common in people over 35 years old and can run in families. Patients with diabetes and kidney disease are more likely to have high blood pressure.

Medication and changes in diet and lifestyle, including quitting smoking, can reduce high blood pressure.

The researchers analysed patterns of blood pressure in 38 populations in the 21 nations. Their research is published online by The British Medical Journal.—Reuters