Hussain SM, et al. - Experts aimed to examine the relationship of female reproductive and hormonal factors with incidence of total knee arthroplasty (TKA) for osteoarthritis. They also assessed if the relationships differ according to overweight/obesity status. Data suggested the reproductive and hormonal factors to be related to knee osteoarthritis risk. At the early reproductive age in normal-weight women and in non-obese women at midlife, these relationships were noted to remain significant.

Methods

• Experts included 22,289 women in the Melbourne Collaborative Cohort Study.
• They collocted the data on age at menarche, pregnancy, parity, years of menstruation, oral contraceptive pill (OCP), menopausal status and hormone replacement therapy (HRT) from 1990-1994.
• By linking cohort records to the National Joint Replacement Registry, incidence of TKA during 2001-2013 was determined.
• They adjusted all analyses for age, BMI at midlife, change in BMI (early reproductive age to midlife), country of birth, physical activity, smoking, and education.

Results

• Herein, 1,208 TKAs for osteoarthritis were identified over 12.7 years.
• Findings suggested that ever pregnancy was related to increased TKA risk (HR=1.32, 95%CI 1.06-1.63).
• Results demonstrated a positive relationship of parity with TKA risk (p for trend=0.003).
• An increased TKA risk was seen in OCP users than non-users (OCP<5 years, HR=1.25, 95%CI 1.08-1.45; OCP ≥5 years, HR=1.17, 95%CI 1.00-1.37).
• Data demonstrated that 1year increase in menstruation was related to 1% decreased TKA risk (HR=0.99, 95%CI 0.97-0.99).
• The significance of these relationships were noted only in normal weight women at early reproductive age.
• According to the results, current HRT users had increased TKA risk than non-users (HR=1.33, 95%CI 1.11-1.60).
• The relationship was significant only in non-obese women at midlife.