title: Contributions of familial rheumatoid arthritis or lupus and environmental factors to risk of rheumatoid arthritis in women: a prospective cohort study.
abstract: OBJECTIVE
  We assessed the contributions of familial rheumatoid arthritis (RA) or lupus and environmental factors to the risk of RA.
  
  
  METHODS
  Among 121,700 women in the Nurses' Health Study, 65,457 provided data on familial RA/lupus. Among these, 493 RA cases (301 seropositive and 192 seronegative) were validated. We estimated hazard ratios (HRs) for RA comparing those with and without familial RA/lupus, adjusting for environmental factors (smoking, alcohol, body mass index [BMI], parity, breastfeeding, menopause, hormone use, early menarche, and menstrual regularity) using Cox proportional hazards models. Population attributable risks (PARs) for RA within this cohort were calculated for familial RA/lupus, smoking, alcohol, BMI, parity, and breastfeeding.
  
  
  RESULTS
  Familial RA/lupus was significantly associated with RA (HR 3.67), seropositive RA (HR 3.90), and seronegative RA (HR 3.95). After adjusting for environmental factors, familial RA/lupus was significantly associated with RA (HR 3.59, 95% confidence interval 2.94-4.37). Smoking >10 pack-years, overweight, BMI, and premenopause status remained significantly associated with RA after adjusting for familial RA/lupus. For RA in this cohort, the PAR for smoking, BMI, alcohol, parity, or breastfeeding collectively was 41%; the PAR due to heredity from familial RA/lupus was 21%.
  
  
  CONCLUSIONS
  In this large, prospective cohort, women with familial RA/lupus had a 4-fold increased risk for RA that remained significant after adjusting for environmental factors. A large proportion of RA risk was attributable to environmental factors, even among those with familial RA/lupus.
authors.affiliation: Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Sparks
authors.forename: Chia-Yen
authors.initials: CY
authors.lastname: Chen
authors.forename: Linda T
authors.initials: LT
authors.lastname: Hiraki
authors.forename: Susan
authors.initials: S
authors.lastname: Malspeis
authors.forename: Karen H
authors.initials: KH
authors.lastname: Costenbader
authors.forename: Elizabeth W
authors.initials: EW
authors.lastname: Karlson
mesh_terms: D000328:Adult; D001172:Arthritis, Rheumatoid / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D016022:Case-Control Studies; D004777:Environment; D005260:Female; D020022:Genetic Predisposition to Disease; D006306:Health Surveys; D006801:Humans; D008180:Lupus Erythematosus, Systemic / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D008875:Middle Aged; D015999:Multivariate Analysis; D010641:Phenotype; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D014481:United States / Q000453:epidemiology
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