Patients taking anti-inflammatory steroid drugs for conditions such as asthma are at a greater risk of heart disease, research suggests.
Glucocorticoids are used to treat asthma
Glucocorticoids are commonly prescribed to alleviate conditions including asthma, rheumatoid arthritis and inflammatory bowel disease.
Scientists from the University of Dundee have found that use of the drugs may increase the risk of developing cardiovascular disease by up to 70%.
The study focused on over 164,000 people from the Tayside area of Scotland.
Nearly half had received at least one glucocorticoid prescription between 1993 and 1996.
The higher the dose of the drug taken, the higher the risk of heart disease appeared to be.
A decade of glucocorticoid use at the highest doses, taken by about 2% of the group, increased the risk of heart disease in over-40s from approx 19 people in every 100 to 32 in 100.
Researcher Professor Brian Walker urged people not to worry.
He said: "These drugs are very effective in the treatment of certain conditions.
"The overall benefits of treatment with glucocorticoids outweighs the risks for most patients.
"However, this study reminds doctors to be cautious when using high doses for extended periods, especially in patients already considered to be at a greater risk of cardiovascular disease."
Glucocorticoids, also called corticosteroids, are a group of anti-inflammatory drugs that are related to cortisol, a natural steroid hormone produced by the body.
They can produce serious side effects including a thinning of the bones, susceptibility to bruising, infections, diabetes, cataracts, glaucoma, high blood pressure and weight gain.
Professor Martyn Partridge, Chief Medical Advisor of the National Asthma Campaign, also warned against drawing firm conclusions from the study.
He said: "The study reported has only been presented in part at a scientific meeting and the full report has not yet been published.
"It is important to note that any perceived risk for those with asthma is with steroid tablets, and at high doses and over a long period, whereas of course most people with asthma are on low doses of inhaled steroids and use steroid tablets only occasionally for very short periods.
"It is also important to realise that such population studies do need to be interpreted with great care."
He said previous studies suggesting people with asthma were at greater risk of heart disease had been skewed by mis-classifying people with smoking-related conditions as asthmatic.
Chicken and egg
Professor Sir Charles George, medical director at the British Heart Foundation, said: "It should be remembered that high dose steroids are very effective at controlling inflammatory processes, some of which themselves carry an increased risk of coronary heart disease e.g. rheumatoid arthritis.
"The study does not make it clear whether it's a "chicken or egg" situation - is it the underlying condition that is causing an increased risk of heart disease, or the medication?
"We fully agree that patients should not be scared off taking their medication and should contact their GPs if they have any concerns."
A spokeswoman for the Arthritis Research Campaign told BBC News Online patients were always prescribed the lowest dose of steroids to treat their condition.
"Unfortunately rheumatoid arthritis can be associated with cardio vascular events, so it might be difficult to know whether it was steroids or the disease itself which caused any heart probems."
The research was presented at a meeting of the British Endocrine Societies in Glasgow.