NEW YORK (Reuters Health) Mar 18 - Among women with rheumatoid arthritis, those who are smokers or ex-smokers are more likely than nonsmokers to develop severe disease, and those with a null polymorphism at the glutathione S-transferase M1 locus (GSTM1) are at risk for the severest disease, study results show.
GSTM1 produces an enzyme that detoxifies carcinogens in tobacco smoke. "The prevalence of GSTM1 varies between different ethnic groups," Dr. Derek Mattey told Reuters Health. "For example, in Africans and African Americans, deletion of the GSTM1 gene is found in only 20% to 25% of individuals, compared to 50% to 55% of Caucasians. The frequency of this deletion in Asian populations is similar to that in Caucasians, although it may be slightly lower in Japanese."

Dr. Mattey, a senior scientist at Staffordshire Rheumatology Centre in the UK, and his colleagues evaluated 164 northern European white women with rheumatoid arthritis. Eighty of the women had never smoked, 35 were ex-smokers and 49 were current smokers.

As in previous studies, rheumatoid arthritis was more severe in patients who were smokers or ex-smokers than in patients who had never smoked, Dr. Mattey's team reports in the March issue of Arthritis & Rheumatism.

Among patients that lacked GSTM1, rheumatoid arthritis severity was significantly greater in smokers and ex-smokers than in nonsmokers. In contrast, in the group that did have the GSTM1 enzyme, smoking did not influence disease severity.

The investigators also found that joint damage became just as severe in women who quit smoking once rheumatoid arthritis was diagnosed as in women who continued to smoke.

"This might suggest that cessation of smoking is of no value, in terms of preventing joint damage, once rheumatoid arthritis has developed," Dr. Mattey commented. "However, it may depend on how much they have smoked in the past, and previous light smokers may gain more benefit from stopping than previous heavy smokers.

"Smoking might be one of a number of possible factors that influence the severity of rheumatoid arthritis, such as diet, hormonal levels and exposure to environmental pollution," Dr. Mattey pointed out. "Also, it is very likely that other genes will be important in the association between smoking and severity of rheumatoid arthritis."

Arthritis Rheum 2002;46:640-646.

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