Exposure to traffic pollution and increased risk of rheumatoid arthritis.
BACKGROUND
Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease that affects approximately 1% of the adult population, and to date, genetic factors explain < 50% of the risk. Particulate air pollution, especially of traffic origin, has been linked to systemic inflammation in many studies.


OBJECTIVE
We examined the association of distance to road, a marker of traffic pollution exposure, and incidence of RA in a prospective cohort study.


METHODS
We studied 90,297 U.S. women in the Nurses' Health Study. We used a geographic information system to determine distance to road at the residence in 2000 as a measure of traffic exposure. Using Cox proportional hazard models, we examined the association of distance to road and incident RA (1976-2004) with adjustment for a large number of potential confounders.


RESULTS
In models adjusted for age, calendar year, race, cigarette smoking, parity, lactation, menopausal status and hormone use, oral contraceptive use, body mass index, physical activity, and census-tract-level median income and house value, we observed an elevated risk of RA [hazard ratio (HR) = 1.31; 95% confidence interval (CI), 0.98-1.74] in women living within 50 m of a road, compared with those women living 200 m or farther away. We also observed this association in analyses among nonsmokers (HR = 1.62; 95% CI, 1.04-2.52), nonsmokers with rheumatoid factor (RF)-negative RA (HR = 1.77; 95% CI, 0.93-3.38), and nonsmokers with RF-positive RA (HR = 1.51; 95% CI, 0.82-2.77). We saw no elevations in risk in women living 50-200 m from the road.


CONCLUSIONS
The observed association between exposure to traffic pollution and RA suggests that pollution from traffic in adulthood may be a newly identified environmental risk factor for RA.
Hart
Jaime E
JE
Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts, USA.
Laden
Francine
F
Puett
Robin C
RC
Costenbader
Karen H
KH
Karlson
Elizabeth W
EW
D000328:Adult; D000397:Air Pollution / Q000009:adverse effects*; D001172:Arthritis, Rheumatoid / Q000139:chemically induced / Q000453:epidemiology*; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D008875:Middle Aged; D016016:Proportional Hazards Models; D012307:Risk Factors; D014186:Transportation