title: The association of parity with osteoarthritis and knee replacement in the multicenter osteoarthritis study.
abstract: OBJECTIVE
  We evaluated the association of parity to both risk of knee replacement (KR) and knee osteoarthritis (OA).
  
  
  METHODS
  The NIH-funded Multicenter Osteoarthritis Study (MOST) is a longitudinal observational study of persons age 50-79 years with either symptomatic knee OA or at elevated risk of disease. Baseline and 30-month knee radiographic OA (ROA) was defined as Kellgren/Lawrence (K/L) grade ≥2 or KR. Women were grouped based by number of births: 0; 1 (reference group); 2; 3; 4; and 5 or more. We examined the relation of parity to the incidence over 30 months of ROA and KR using a Poisson regression model. Generalized estimating equations (GEE) were used to control for correlation between two knees within a subject. We adjusted for age, BMI, race, education, occupation, baseline estrogen use, clinical site, injury, and for KR analyses WOMAC pain and use of pain medication.
  
  
  RESULTS
  Among 1618 women who reported parity information, mean age was 62.6 years, mean BMI 30.7 kg/m(2), mean WOMAC pain subscale score 3.7 at baseline. There were 115 KRs and 134 cases of incident knee ROA over 30 months. The relative risk of incident KR was 2.7 times as high (95% CI: 1.0, 7.3) and relative risk of incident knee ROA was 2.6 times as high (95% CI: 1.2, 5.3) among women with five to 12 children compared with those with one birth.
  
  
  CONCLUSIONS
  Parity in women at risk for OA is associated with both incident ROA and KR, particularly for those with more than four children.
authors.affiliation: University of California, Davis School of Medicine, USA. Electronic address: barton.wise@ucdmc.ucdavis.edu.
authors.forename: B L
authors.initials: BL
authors.lastname: Wise
authors.forename: J
authors.initials: J
authors.lastname: Niu
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: D T
authors.initials: DT
authors.lastname: Felson
authors.forename: L A
authors.initials: LA
authors.lastname: Bradley
authors.forename: N
authors.initials: N
authors.lastname: Segal
authors.forename: J
authors.initials: J
authors.lastname: Keysor
authors.forename: M
authors.initials: M
authors.lastname: Nevitt
authors.forename: N E
authors.initials: NE
authors.lastname: Lane
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000706:statistics & numerical data*; D015992:Body Mass Index; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008137:Longitudinal Studies; D008875:Middle Aged; D015999:Multivariate Analysis; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000453:epidemiology*; D010147:Pain Measurement; D010298:Parity; D016012:Poisson Distribution; D011859:Radiography; D012044:Regression Analysis; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
keywords: Joint replacement; Knee; Osteoarthritis; Parity
references.citation: Ann Rheum Dis. 1996 Sep;55(9):673-6
references.pmid: 8882148
references.citation: Am J Epidemiol. 1988 Jul;128(1):179-89
references.pmid: 3381825
references.citation: Arthritis Rheum. 2007 Sep;56(9):2986-92
references.pmid: 17763427
references.citation: Osteoarthritis Cartilage. 2011 Oct;19(10):1176-82
references.pmid: 21835256
references.citation: Obstet Gynecol. 1995 Nov;86(5):834-8
references.pmid: 7566859
references.citation: Br J Rheumatol. 1993 May;32(5):366-70
references.pmid: 8495255
references.citation: JAMA. 1994 Jun 8;271(22):1747-51
references.pmid: 8196117
references.citation: Ann Rheum Dis. 2009 Jul;68(7):1165-70
references.pmid: 18957480
references.citation: J Rheumatol. 2008 Oct;35(10):2047-54
references.pmid: 18793000
references.citation: Ann Rheum Dis. 1996 Sep;55(9):671-3
references.pmid: 8882147
references.citation: Health Serv Res. 1996 Jun;31(2):125-40
references.pmid: 8675435
references.citation: Osteoarthritis Cartilage. 2011 Nov;19(11):1307-13
references.pmid: 21872670
references.citation: Obes Res. 2004 Dec;12(12):2041-53
references.pmid: 15687406
references.citation: Int J Obes Relat Metab Disord. 2004 Apr;28(4):525-35
references.pmid: 14770188
references.citation: J Epidemiol Community Health. 2003 Oct;57(10):823-30
references.pmid: 14573590
references.citation: J Arthroplasty. 1996 Jan;11(1):34-46
references.pmid: 8676117
references.citation: Epidemiol Rev. 2000;22(2):261-74
references.pmid: 11218377
references.citation: BMJ. 2009 Aug 21;339:b2844
references.pmid: 19700505
references.citation: Int J Obes Relat Metab Disord. 1994 Aug;18(8):561-9
references.pmid: 7951478