Rheumatoid factor seropositivity is inversely associated with
oral contraceptive use in women without rheumatoid arthritis
Shailaja S Bhatia, Darcy S Majka, John M Kittelson, Lezlie A Parrish, Elizabeth D Ferucci,
Kevin D Deane, William P Arend, Marian Rewers, V Michael Holers, Jill M Norris
............................................................... ............................................................... .....
Ann Rheum Dis 2007;66:267–269. doi: 10.1136/ard.2006.060004
Objectives: To examine whether oral contraceptive use is
associated with the presence of serum rheumatoid factor in
women of reproductive age without rheumatoid arthritis.
Methods: 304 women selected from parents of children who
were at increased risk of developing type 1 diabetes were
studied, because they were enriched with the human leucocyte
antigen-DR4 allele, a susceptibility marker for both type 1
diabetes and rheumatoid arthritis. Participants visited a clinic
where blood was drawn for rheumatoid factor testing, and
exposure data were collected via questionnaires. A medical
history and joint examination were performed to rule out
rheumatoid arthritis. Participants and examiners were unaware
of the participants’ rheumatoid factor status at the time of
examination and questionnaire.
Results: Use of oral contraceptives at any time was inversely
associated with rheumatoid factor positivity (adjusted odds
ratio (OR) 0.2, 95% confidence interval (CI) 0.07 to 0.52)
independent of age, education and smoking. Smoking
>20 pack-years was also associated with rheumatoid factor
positivity (adjusted OR 56.38, 95% CI 4.31 to 736.98)
compared with never smoking. Smoking 1–19 pack-years
was not associated with a positive rheumatoid factor.
Conclusions: Our results suggest that oral contraceptive use,
and possibly cigarette smoking, act early in the development of
the immune dysregulation that occurs in rheumatoid arthritis.
and individuals with stable increases in rheumatoid factor have
an increased incidence of rheumatoid arthritis,1suggesting that
factors regulating rheumatoid factor production may have an
important early role in the pathogenesis of rheumatoid
Specific major histocompatibility complex class II molecule
DRB1 alleles encoding the shared epitope are the most
important genetic risk factors for the development of rheuma-
toid arthritis.2However, most individuals carrying the shared
epitope do not develop rheumatoid arthritis, suggesting that a
genetic predisposition is necessary but not sufficient for disease.
Several epidemiological studies have investigated the asso-
ciation between oral contraceptives and rheumatoid arthritis.3–7
Although most studies have shown a protective effect, other
studies have failed to find such an association. Methodological
issues and potential biases inherent in case–control studies may
have resulted in these varying results.3 4
Cigarette smoking has been associated with rheumatoid
factor seropositivity and other measures of disease severity in
and with the risk of seropositive
However, the association between
heumatoid factor is a well-established test used in the
diagnosis and prognosis of rheumatoid arthritis. In
addition, rheumatoid factor precedes rheumatoid arthritis,
cigarette smoking and rheumatoid factor positivity in partici-
pants without rheumatoid arthritis has not been definitively
We conducted a cross-sectional study of healthy women and
examined whether exposure to sex hormones and smoking
were associated with the presence of rheumatoid factor.
The study population comprised 304 women selected from
parents of children enrolled in the Diabetes Autoimmunity
Study in the Young (DAISY), a birth cohort of children with an
increased risk of type 1 diabetes.12We selected the DAISY
parental population because it is enriched for the human
leucocyte antigen (HLA)-DR4 allele, a susceptibility marker for
both type 1 diabetes and rheumatoid arthritis. The DAISY
parent cohort was assembled as follows: newborns at increased
risk for type 1 diabetes were identified at St Joseph’s Hospital,
Denver, Colorado, USA, by screening umbilical cord blood
samples for the diabetes susceptibility HLA alleles, DR4 and
DR3. Newborns possessing either allele were asked to partici-
pate in the follow-up study. Additionally, children having a
first-degree relative with type 1 diabetes also enrolled in the
DAISY cohort. All parents of children currently enrolled in the
DAISY study and who had their blood previously drawn and
stored were eligible to participate in this study. The Colorado
Multiple Institutional Review Board approved this study, and
informed consent was obtained from all study participants.
Six women self-reported having rheumatoid arthritis. After
confirmation via reviews of medical records, based on either the
diagnosis of a board-certified rheumatologist or classification
by the 1987 American College of Rheumatology (ACR) criteria,
they were excluded from this cohort. The remaining 298
women without self-reported rheumatoid arthritis were inter-
viewed and examined to assess for symptoms or signs
consistent with rheumatoid arthritis (according to the 1987
ACR criteria, during a single study visit). Participants and
examiners were unaware of the participants’ rheumatoid factor
status at the time of examination and questionnaire. The
interview included questions about morning stiffness, joint
swelling, joint pain, subcutaneous nodules and past rheuma-
toid factor serology. Participants underwent a 68-joint count
examination by a study rheumatologist or a study nurse
practitioner trained in joint examinations. None of the 298
women examined met the criteria for rheumatoid arthritis
based on the 1987 ACR classification criteria.
History and current data regarding reproductive, hormonal,
smoking and coffee consumption exposures were obtained at
Abbreviations: ACR, American College of Rheumatology; DAISY,
Diabetes Autoimmunity Study in the Young; HLA, human leucocyte antigen
the time of the clinic visit by a self-administered questionnaire.
Race/ethnicity was categorised as non-Hispanic white or other,
which included Hispanic, black, Asian and biracial women.
Exposure to oral contraceptives was defined as a positive
history for ‘‘ever’’ use of oral contraceptives. Duration of oral
contraceptive use was the total number of years of use of oral
contraceptives over the participant’s lifetime. Women were
considered ‘‘never smokers’’ if they smoked ,100 cigarettes in
their lifetime. For women who reported that they smoked .100
cigarettes, we further quantified exposure into 1–19 and
Measurement of autoantibodies
Rheumatoid factor was measured in sera of study participants
using nephelometry according to the manufacturer’s specifica-
tions (Dade Behring, Newark, Delaware, USA). A concentration
of >15 IU/ml was identified as a positive test based on results
from controls consisting of blood bank donors showing 5%
positivity (Dade Behring N Latex RF package insert). Only
positive results confirmed with a blinded duplicate were
considered positive for these analyses.
HLA-DR4 typing was performed at Roche Molecular, California,
USA, using methods described previously.12All HLA-DR4-
positive samples were evaluated at the Benaroya Research
Institute, Virginia Mason, Seattle, Washington, USA, for
screening for subtypes that contain the shared epitope. For
determination of DR4 subtypes, the polymerase chain reaction
product was treated with shrimp alkaline phosphatase (Roche
Applied Science, Indianapolis, Indiana, USA) and Exonuclease
I (Epicentre), followed by DNA sequencing using Big Dye
Terminator V.1.1 Cycle Sequencing (Applied Biosystems, Foster
City, California, USA). Participants with the following alleles
were considered to be shared epitope positive: DRB1*0401,
DRB1*0404, DRB1*0405 or DRB1*0408.
All univariate and multivariate analyses were performed with
SAS V.9.1. Using multivariate logistic regression analyses, we
examined the independent effect of oral contraceptive use and
cigarette smoking on rheumatoid factor status, considering the
variables listed in table 1 as potential confounders and
covariates. Age and education were retained in the final model
to adjust for any effect they had on rheumatoid factor
positivity, oral contraceptive use and smoking.
Of the 298 women, 31 (10.4%) had a positive rheumatoid
factor. Women who ever used oral contraceptives were less
likely to be rheumatoid factor positive than women who never
used oral contraceptives (odds ratio (OR) 0.21, 95% confidence
interval (CI) 0.09 to 0.51; table 1). Women who smoked
>20 pack-years were more likely to be rheumatoid factor
positive than women who never smoked (OR 12.48, 95% CI
1.98 to 78.8).
After adjusting for age, education and smoking, ever use of
oral contraceptives was significantly inversely associated with
the presence of rheumatoid factor (adjusted OR 0.2, 95% CI
0.07 to 0.52; table 1). Smoking >20 pack-years was also
independently associated with a positive rheumatoid factor
compared with never smoking (adjusted OR 56.38, 95% CI 4.31
Risk factors for rheumatoid factor seropositivity in the study cohort of 298 women
(n=267) p Value
Final model adjusted
OR? (95% CI)
Mean (SD) age (years)
Ethnicity, n (%)
Education (12 years, n (%)??
Shared epitope positive, n (%)``
History of T1DM, n (%)
History of T1DM in FDR, n (%)
History of RA in FDR, n (%)
Ever use of OC, n (%)
37.7 (6.2)38.2 (6)0.70`
0.99 (0.93 to 1.05)1
0.98 (0.91 to 1.05)
1.41 (0.51 to 3.94)
0.44 (0.10 to 1.95)
0.66 (0.31 to 1.44)
1.90 (0.72 to 5)
1.01 (0.41 to 2.45)
1.57 (0.51 to 4.88)
0.21 (0.09 to 0.51)
0.18 (0.02 to 1.52)
0.20 (0.07 to 0.52)
Cigarette smoking, n (%)
0.61 (0.24 to 1.56)
12.48 (1.98 to 78.80)
0.85 (0.32 to 2.28)
56.38 (4.31 to 736.98)
Mean (SD) duration of OC use (years)11
Mean (SD) number of pregnancies
History of breast feeding, n (%)
Mean (SD) duration of breastfeeding
Ever use of injectable hormones, n (%)
Ever use of hormone replacement
therapy, n (%)***
Mean (SD) consumption of caffeinated
Mean (SD) consumption of decaffeinated
0.98 (0.90 to 1.06)1
0.91 (0.71 to 1.16)1
0.92 (0.26 to 3.26)
0.99 (0.96 to 1.01)1
0.84 (0.31 to 2.28)
1.32 (0.37 to 4.72)
0.89 (1.52) 1.19 (2.28) 0.33`
0.91 (0.70 to 1.18)1
0.23 (0.67)0.14 (0.47) 0.48`
1.34 (0.73 to 2.46)1
FDR, first-degree relative; OC, oral contraceptive; RA, rheumatoid arthritis; T1DM, type 1 diabetes mellitus.
*OR calculated using univariate logistic regression; ?each variable was adjusted for the other variables in the final model; `p Value calculated using Student’s t test; 1OR
was calculated for any 1-unit increase in the variable (ie, year, for age and oral contraceptive duration, and month, for breast-feeding duration); ?p value calculated
using x2test of heterogeneity for a 26X comparison, with X being the number of categories of the risk factor; **includes Hispanic, black, Asian and biracial women;
??data on education available for 281 subjects; ``shared epitope-positive subjects have an HLA-DR4 allele known to encode the shared epitope (DRB1*0401,
DRB1*0404, DRB1*0405 or DRB1*0408); 11mean of 268 women who have ever taken oral contraceptives; ??mean of 271 women who have ever breast-fed; ***data
on hormone replacement therapy were missing for one individual.
268 Bhatia, Majka, Kittelson, et al
We evaluated associations with the presence of rheumatoid
factor, rather than clinical disease. Studies showing rheumatoid
factor antecedent to the onset of clinical disease support this
approach.1Our findings are consistent with previous studies
that found a protective effect of oral contraceptive use on the
development of rheumatoid arthritis.3–7Our unique finding that
oral contraceptives are inversely associated with the presence of
rheumatoid factor in healthy women suggests that these
exogenous hormones may act very early in the development
of the immune dysregulation that occurs in rheumatoid
We did not find a significant ‘‘dose–response’’ effect with the
duration of oral contraceptive use in our population, although
in oral contraceptive users, rheumatoid factor-positive women
had used oral contraceptives for a slightly shorter duration than
rheumatoid factor-negative women. This may suggest a thresh-
old effect, whereby the longer durations reported by the women
carried little influence beyond the threshold duration.
The precise mechanism behind the protective effect of oral
contraceptives on rheumatoid arthritis is unknown, but it may
be that oral contraceptives, which are largely synthetic
hormones, drive the immune system towards T helper 2
cytokine responses, and decreased production of proinflamma-
tory and other cytokines leading to T helper 1-associated
rheumatoid arthritis-specific cellular autoimmunity.13
We observed an association between rheumatoid factor
positivity and smoking only in the heaviest smokers. Previous
studies that have examined an association between rheumatoid
factor and cigarette smoking in individuals without rheumatoid
arthritis are conflicting.10 11However, studies on seropositive
rheumatoid arthritisand smoking
between pack-years smoked and rheumatoid factor levels14;
and another study found an association between smoking and
seropositive rheumatoid arthritis only in subjects who had
smoked >20 years at an intensity of 6–9 cigarettes/day.15
Although our study was limited by the small number of heavy
smokers, our results, considered in combination with the
findings from previous studies, indicate that there might be a
cumulative or threshold dose effect of smoking.
Our study population was selected through children at
increased risk for type 1 diabetes, and thus enriched with
HLA-DR4. However, because the DAISY cohort was identified
and assembled during a population-based screening, it was
therefore established without prior bias relative to rheumatoid
arthritis. Also, rheumatoid factor-positive and rheumatoid
factor-negative women for this study were drawn from the
Additionally, our study was not susceptible to recall and
interviewer bias because the exposure data were collected
without knowledge of the autoantibody status by the individual
or the interviewer.
Given that all the women in this study were selected from a
cohort of largely Caucasian parents who had given birth to at
least one child, wider applicability of these results may be
limited. Although these results are consistent with the findings
of previous investigators, studies showing a protective effect of
oral contraceptive use on rheumatoid factor status in a more
ethnically mixed population and in nulliparous women would
further support our findings. Given that our study was cross
sectional, we cannot discern the temporal sequence between
Prospective studies designed to follow-up individuals for the
development of rheumatoid factor and rheumatoid arthritis are
necessary to evaluate these hypotheses further. Nevertheless,
our results support the hypotheses that oral contraceptive use is
protective, and that cigarette smoking may confer increased
risk very early in the rheumatoid arthritis disease course.
Shailaja S Bhatia*, John M Kittelson, Jill M Norris, Department of
Preventive Medicine and Biometrics, University of Colorado at Denver and
Health Sciences Center, Denver, Colorado, USA
Darcy S Majka*, Division of Rheumatology, Northwestern University,
Feinberg School of Medicine, Chicago, Illinois, USA
Lezlie A Parrish, Kevin D Deane, William P Arend, V Michael Holers,
Division of Rheumatology, University of Colorado at Denver and Health
Sciences Center, Denver, Colorado, USA
Elizabeth D Ferucci, Office of Alaska Native Health Research, Alaska
Native Tribal Health Consortium, Anchorage, Alaska, USA
Marian Rewers, Barbara Davis Center for Childhood Diabetes, University
of Colorado at Denver and Health Sciences Center, Denver, Colorado,
*These authors contributed equally to the study.
Funding: These studies were supported by NIH U-19 AI50864, T-32
AR07534, N-01 AR42218, P-60 AR47784, P-30 AR47363, R-01
DK32493 (DAISY), DERC P30 DK57516, Arthritis Foundation/American
College of Rheumatology Physician Scientist Development Award, NIH K12
RR017707 (Northwestern University), K23 AR051461 and the Smyth
Professorship in Rheumatology.
Competing interests: None.
Correspondence to: Dr Jill M Norris, Department of Preventive Medicine
and Biometrics, University of Colorado at Denver and Health Sciences
Center, Denver, 4200 East Ninth Avenue, Box B119, Denver, CO 80262,
Accepted 13 July 2006
Published Online First 25 July 2006
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