Relationship between body adiposity measures and risk of primary knee and hip replacement for osteoarthritis: a prospective cohort study.
BACKGROUND
Total joint replacement is considered a surrogate measure for symptomatic end-stage osteoarthritis. It is unknown whether the adipose mass and the distribution of adipose mass are associated with the risk of primary knee and hip replacement for osteoarthritis. The aim of the present investigation was to examine this in a cohort study.


METHODS
A total of 39,023 healthy volunteers from Melbourne, Australia were recruited for a prospective cohort study during 1990 to 1994. Their body mass index, waist circumference, and waist-to-hip ratio were obtained from direct anthropometric measurements. The fat mass and percentage fat were estimated from bioelectrical impedance analysis. Primary knee and hip replacements for osteoarthritis between 1 January 2001 and 31 December 2005 were determined by data linkage to the Australian Orthopaedic Association National Joint Replacement Registry. Cox proportional hazards regression models were used to estimate the hazard ratios (HRs) for primary joint replacement associated with each adiposity measure.


RESULTS
Comparing the fourth quartile with the first, there was a threefold to fourfold increased risk of primary joint replacement associated with body weight (HR = 3.44, 95% confidence interval (CI) = 2.83 to 4.18), body mass index (HR = 3.44, 95% CI = 2.80 to 4.22), fat mass (HR = 3.51, 95% CI = 2.87 to 4.30), and percentage fat (HR = 2.99, 95% CI = 2.46 to 3.63). The waist circumference (HR = 2.77, 95% CI = 2.26 to 3.39) and waist-to-hip ratio (HR = 1.46, 95% CI = 1.21 to 1.76) were less strongly associated with the risk. Except for the waist-to-hip ratio, which was not significantly associated with hip replacement risk, all adiposity measures were associated with the risk of both knee and hip joint replacement, and were significantly stronger risk factors for knee.


CONCLUSIONS
Risk of primary knee and hip joint replacement for osteoarthritis relates to both adipose mass and central adiposity. This relationship suggests both biomechanical and metabolic mechanisms associated with adiposity contribute to the risk of joint replacement, with stronger evidence at the knee rather than the hip.
Wang
Yuanyuan
Y
Department of Epidemiology and Preventive Medicine, Monash University, Central and Eastern Clinical School, Alfred Hospital, Melbourne, VIC 3004, Australia. wangyyau@yahoo.com.au.
Simpson
Julie Anne
JA
Wluka
Anita E
AE
Teichtahl
Andrew J
AJ
English
Dallas R
DR
Giles
Graham G
GG
Graves
Stephen
S
Cicuttini
Flavia M
FM
D050154:Adiposity / Q000502:physiology*; D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D019645:Arthroplasty, Replacement, Knee; D015992:Body Mass Index; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000209:etiology / Q000601:surgery; D020370:Osteoarthritis, Knee / Q000209:etiology / Q000601:surgery; D050177:Overweight / Q000150:complications; D012307:Risk Factors; D055105:Waist Circumference; D049629:Waist-Hip Ratio