Environmental risk factors differ between rheumatoid arthritis with and without auto-antibodies against cyclic citrullinated peptides

August 1, 2006

Environmental risk factors differ between rheumatoid arthritis with

and without auto-antibodies against cyclic citrullinated peptides

Arthritis Research & Therapy 2006, 8:R133 doi:10.1186/ar2022

Published

27 July 2006

Abstract (provisional)

The complete article is available as a provisional PDF. The fully

formatted PDF and HTML versions are in production.

The aim of the study was to evaluate new and previously hypothesized

non-genetic risk factors for serologic subtypes of rheumatoid

arthritis (RA) defined by the presence or absence of auto-antibodies

to cyclic citrullinated peptides (CCP). In a national case-control

study, we included 515 patients recently diagnosed with RA according

to the American College of Rheumatology 1987 classification criteria

and 769 sex- and age-matched population controls. Telephone

interviews provided information about non-genetic exposures, and

serum samples for patients were tested for anti-CCP-antibodies.

Associations between exposure variables and risk of anti-CCP-positive

and anti-CCP-negative RA were evaluated using logistic regression. A

series of RA subtype-specific risk factors were identified. Tobacco

smoking (odds ratio (OR)=1.65; 95% confidence interval: 1.03-2.64,

for >20 vs. 0 pack-years) was selectively associated with risk of

anti-CCP-positive RA, whereas alcohol consumption exhib-ited an

inverse dose-response association with this RA subtype (OR=1.98,

1.22-3.19, for 0 vs. >0-5 drinks/week). Furthermore, coffee

consumption (OR=2.18; 1.07-4.42, for >10 vs. 0 cups/day), ever use of

oral contraceptives (OR=1.65; 1.06-2.57) and having a first-degree

relative with schizophrenia (OR=4.18; 1.54-11.3) appeared more

strongly associated with risk of anti-CCP-positive RA. Obesity was

selectively associated with risk of anti-CCP-negative RA, with obese

individuals being at more than 3-fold increased risk of this subtype

compared with normal weight individuals (OR=3.45; 1.73-6.87). Age at

menarche was the only examined factor that was significantly

associated with both serologic subtypes of RA (p-trends=0.01); women

with menarche at age & #8805;15 years had about twice the risk of

either RA subtype compared with women with menarche at age & #8804;12

years. Major differences in risk factor profiles suggest distinct

etiologies for anti-CCP-positive and anti-CCP-negative RA.

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