Lowering cholesterol levels, normally promoted as an important measure to stave off the threat of heart disease and strokes, may increase the risk of death for older people, says a study published today.

A study published in the Lancet casts doubts on the scientific justification for campaigns to reduce levels in people over 70.

The authors concede they can not explain their results from a study in Hawaii which compared concentrations of cholesterol in 3,572 Japanese/American men aged 71 to 93 over 20 years. But they suggest a more "prudent" approach should be taken on advising and treating patients until more information is available.

But the British Heart Foundation warned that overall cholesterol levels among Britons were still far too high.

Cholesterol is needed to create bile acids which digest fat. It is mainly produced in the liver but also comes from food such as meat, eggs and shellfish. There are two types - one which clogs arteries and increases the risk of disease, the other which helps remove "bad" cholesterol from the blood and prevent fatty build-ups.

Levels in the blood are measured by a chemical formulation abbreviated to mmol/L and the foundation says that they should be about 5mmol/L, but the UK average is about 5.8 rising to 6.3 among people over 75.

In the Lancet study, average cholesterol levels decreased as the men got older. But the lowest levels were associated with higher death rates. After allowing for age, men in the lowest quarter for their concentration of cholesterol had an annual death rate of 68.3 per 1000 of the population, while those with the highest had an annual rate of 43.3 per 1000, a 35% difference.

The researchers suggested that men with low cholesterol over 20 years had the worst outlook. They warned against reducing cholesterol to less than 4.65mmol/L in older people.

But Alison Shaw, cardiac nurse adviser to the Heart Foundation, said most participants in the Hawaiian study seemed to already have cholesterol levels much lower than the 5mmol/L advised here.