One in three severe rheumatoid arthritis cases 'due to smoking'
Published on 14 December 2010
More than a third of severe cases of rheumatoid arthritis can be attributed to smoking, new research suggests.
Smoking is already known to be a risk factor for the autoimmune disease, in which the body's immune system produces inflammation that attacks tissues in the joints.
Now, a study in the Annals of the Rheumatic Diseases indicates that a significant proportion of severe cases are due to smoking, along with more than half of cases in people with a genetic predisposition to the disease.
Researchers at Sweden's Karolinska Institute analysed more than 1,200 people with rheumatoid arthritis, as well as a further 871 volunteers who were of a similar age and sex but did not have the disease.
Participants were recruited from 19 health clinics in Sweden and were aged between 18 and 70 years.
They provided blood samples to assess their genetic susceptibility to rheumatoid arthritis and determine the severity of their disease, as well as giving information on their history of smoking.
The researchers found that 61 per cent of rheumatoid arthritis patients tested positive for a protein called anticitrullinated protein/peptide antibody (ACPA), which shows they had the most severe form of the disease.
Analysis revealed that the heaviest smokers in the study (who smoked 20 a day for at least 20 years) had a more than 2.5-fold increased risk of the most severe form of the disease.
Ex-smokers were less likely to have severe rheumatoid arthritis, although those who had smoked the most before giving up still had a relatively high risk.
Overall, the study authors estimated that smoking accounted for one in five cases of rheumatoid arthritis, and 35 per cent of severe cases of the disease.
This means that the risk of rheumatoid arthritis among smokers is similar to their risk of developing heart disease.
A spokeswoman for Arthritis Research UK said: "There are a number of risk factors that influence the likelihood of someone developing rheumatoid arthritis, such as genetic factors, but we've also known for some time that lifestyle factors such as smoking, and also eating a lot of red meat and drinking large amounts of caffeine, may affect the risk of developing the disease.
"As there is little you can do about changing your genetic make-up, it seems sensible to reduce the other risk factors that you actually have some control over. So stopping smoking would be one obvious way of doing this."