Smoking & RA

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Smoking Behind More Than a Third of Severe Rheumatoid Arthritis Cases

ScienceDaily (Dec. 15, 2010) — Smoking accounts for more than a third

of cases of the most severe and common form of rheumatoid arthritis,

indicates research published online in the ls of the Rheumatic

Diseases.

And it accounts for more than half of cases in people who are

genetically susceptible to development of the disease, finds the study.

The researchers base their findings on more than 1,200 people with

rheumatoid arthritis and 871 people matched for age and sex, but free

of the disease. The patients came from 19 health clinics in south and

central Sweden, while their healthy peers were randomly selected from

the population register. All the participants were aged between 18 and

70.

They were quizzed about their smoking habits and grouped into three

categories, depending on how long they had smoked.

Blood samples were taken to assess all the participants' genetic

profile for susceptibility to rheumatoid arthritis and to gauge the

severity of their disease, as indicated by their antibody levels.

More than half of those with rheumatoid arthritis (61%) had the most

severe form of the disease, which is also the most common form, as

judged by testing positive for anticitrullinated protein/peptide

antibody (ACPA).

Those who were the heaviest smokers -- 20 cigarettes a day for at

least 20 years -- were more than 2.5 times as likely to test positive

for ACPA. The risk fell for ex-smokers, the longer they had given up

smoking. But among the heaviest smokers, the risk was still relatively

high, even after 20 years of not having smoked.

Based on these figures, the researchers calculated that smoking

accounted for 35% of ACPA positive cases, and one in five cases of

rheumatoid arthritis, overall.

Although this risk is not as high as for lung cancer, where smoking

accounts for 90% of cases, it is similar to that for coronary artery

heart disease, say the authors.

Among those with genetic susceptibility to the disease, and who tested

positive for ACPA, smoking accounted for more than half the cases

(55%). Those who smoked the most had the highest risk.

The authors point out that several other environmental factors may

contribute to an increased risk of rheumatoid arthritis, including air

pollutants and hormonal factors. But they suggest that their findings

are sufficient to prompt those with a family history of rheumatoid

arthritis to be advised to give up smoking.