Table 3 Relative risk of joint replacement for osteoarthritis according to reproductive history
Population at riskHip replacementKnee replacement
CasesRR* (95% CI)CasesRR* (95% CI)
Parity:
Nulliparous141 24112381.007731.00
1184 06816441.00 (0.93 to 1.08)12731.21 (1.10 to 1.32)
2548 11546801.01 (0.95 to 1.08)36491.27 (1.18 to 1.38)
3281 26527431.04 (0.97 to 1.11)24861.43 (1.32 to 1.55)
4 or more148 52117911.10 (1.02 to 1.19)17751.46 (1.34 to 1.59)
p Linear trend0.004<0.001
Age at menarche, years:
⩽11261 44425611.09 (1.03 to 1.16)24871.15 (1.08 to 1.22)
12226 88020081.0016571.00
13311 15027731.00 (0.94 to 1.06)21250.97 (0.91 to 1.03)
14262 45424461.02 (0.96 to 1.08)18090.96 (0.90 to 1.03)
15+217 06020871.01 (0.95 to 1.07)16621.03 (0.96 to 1.11)
p Linear trend0.02<0.001
Menopausal status:†
Pre/peri134 9101921.00891.00
Post108 6131110.97 (0.77 to 1.24)410.76 (0.52 to 1.10)
Age at menopause, years:‡
⩽48113 85813941.0010591.00
49–51107 81512411.01 (0.93 to 1.09)8600.98 (0.89 to 1.07)
52+128 91315350.98 (0.91 to 1.06)10990.92 (0.84 to 1.00)
p Linear trend0.50.06
  • *Adjusted for age, recruitment region, height, BMI, alcohol, smoking, socioeconomic status, oral contraceptive use, HRT use and parity, and age at menarche as appropriate. †In 243 523 women aged <55 years at recruitment who never used HRT with follow-up censored at age 55 years. ‡In 350 586 postmenopausal women (with a natural menopause) who never used HRT and were aged over 52 years at recruitment.

  • RR, relative risk.