73.
The genetic influence on symptomatic hip and knee osteoarthritis
differs by joint site and sex. A nationwide population and register based
study in Danish twins.
Søren Glud Skousgaard, Lars Peter Brandt, Axel Skytthe, Søren Overgaard
Orthopedic Research Unit & Reseach Unit for Occupational and
Environmental Medicine Odense University Hospital; Occupational and
Environmental Medicine, Odense University Hospital; The Danish Twin
Register, University of Southern Denmark; Orthopedic Research Unit, Odense
University Hospital
Background:
Little is known about the genetic influence on symptomatic hip
and knee osteoarthritis or if genetic risk factors affects men and women
differently.
Purpose / Aim of Study:
To examine the genetic influence on symptomatic
hip and knee osteoarthritis in men and women.
Materials and Methods:
Twins from The Danish Hip and Knee Arthroplasty
Registers were identified by merging the two registers with The Danish Twin
Register and all twins with a diagnosis of primary hip or knee OA were
sampled and analysed. Tetrachoric correlations and probandwise concordance
rates were calculated. We examined our twin data in the ACE, AE, CE and E
models separately by joint site and sex.
Findings / Results:
The twin hip population comprised 93.228 non-cases and
835
cases with 428 female cases and 407 male cases, p=0.37. The twin knee
population comprised 95.956 non-cases and 733 cases with 425 female cases
and 308 male cases, p<0.001. Tetrachoric correlations and probandwise
concordant rates in hip twin pairs were significantly higher in MZ males and
MZ females compared to DZ males and DZ females indicating a substantial
genetic influence on hip OA in both sexes. In knee OA no difference between
MZ and DZ males in either tetrachoric correlations nor probandwise
concordance rates were observed, but in female MZ and DZ twin pairs the
differences were significant indicating a substantial genetic influence in
women but not in men. In hip OA the best fitting model was the AE model in
both sexes. In males A accounted for 0.70 and E for 0.30; in women A
accounted for 0.67 and E for 0.33. In males knee OA the best model fit was in
the CE model, C accounting for 0.47 and E for 0.53; in women the AE model
had the best fit, A accounting for 0.74 and E for 0.26.
Conclusions:
The genetic influence on hip and knee osteoarthritis differs
significantly by sex and joint site.
