Link Between Smoking, Arthritis Severity Explained

[Guest guest]

Link Between Smoking, Arthritis Severity Explained

Fri Mar 15, 2:08 PM ET

By Faith Reidenbach

NEW YORK (Reuters Health) - Among women with rheumatoid arthritis, those who are

smokers or ex-smokers and also

lack a certain detoxifying enzyme are more likely than nonsmokers to develop

severe disease, study results show.

The gene in question is GSTM1, which produces an enzyme that detoxifies

cancer-causing chemicals in tobacco smoke.

It is not uncommon for a person to be born without this gene.

" The prevalence of GSTM1 varies between different ethnic groups, " Dr.

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. "

Previous studies have shown that heavy smoking may influence the severity of

rheumatoid arthritis. Unlike osteoarthritis,

which is caused by the general wear and tear of aging, in rheumatoid arthritis

the patient's immune system goes awry,

attacking the joints and causing inflammation and stiffness. Mattey, a senior

scientist at Staffordshire Rheumatology

Centre in the UK, and his colleagues set out to discover what smoking has to do

with this disease process.

They 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, Mattey's team reports in the March issue of Arthritis &

Rheumatism. The team made the

assessment using measures such as x- rays of joint damage and patients' ability

to perform everyday tasks.

The researchers then divided the patients into those with or without the GSTM1

enzyme. In the group that lacked the

enzyme, they found that 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 difference may be partly influenced by the body's production of a substance

called rheumatoid factor, the research

team suggests. Normally, the body produces molecules called antibodies to fight

foreign organisms such as bacteria and

viruses. One of the problems in rheumatoid arthritis is that the body produces

antibodies against one of its own antibodies,

IgG. These autoantibodies, as they are known, are also called rheumatoid factor.

" The majority of rheumatoid arthritis patients, 60% to 80%, are positive for

rheumatoid factor, " Mattey said. " The role of

rheumatoid factor in the development of rheumatoid arthritis is still unclear,

but it is generally considered to be a marker of

more severe disease. "

As in previous studies, the researchers determined that current smokers were

significantly more likely to have rheumatoid

factor than patients who had never smoked, and the number of years of smoking

was associated with the amount of

rheumatoid factor. A brand-new finding was that these facts held true only for

patients who lacked the GSTM1 enzyme.

The explanation might be that chemicals in smoke damage IgG, prompting the body

to produce more rheumatoid factor,

the researchers propose. This would be much less of a problem in people who have

the GSTM1 enzyme, which

detoxifies these damaging chemicals.

Another finding from the study was 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, " 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.

" It needs to be borne in mind that this was a small study on a group of female

patients in one particular geographic area.

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, " he pointed out.

" Also, it is very likely that other genes will be important in the association

between smoking and severity of rheumatoid

arthritis, " he said. " Further studies are clearly needed to establish whether

our findings apply to other populations of

individuals with rheumatoid arthritis, and if other genetic factors are

important. "

SOURCE: Arthritis & Rheumatism 2002;46:640-646.