Oral Presentation 29th Australian and New Zealand Bone and Mineral Society Annual Scientific Meeting 2019

Muscle performance improves predictive accuracy of the Garvan fracture risk calculator: A reclassification analysis (#20)

Dima Alajlouni 1 2 , Dana Bliuc 2 , Thach Tran 2 , John A. Eisman 1 2 3 , Tuan V. Nguyen 1 2 4 5 , Jackie R. Center 1 2 3
  1. Faculty of Medicine, UNSW Sydney, Sydney, NSW, Australia
  2. Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
  3. Clinical School, St Vincent's Hospital, Sydney, NSW, Australia
  4. Clinical Translation and Advanced Education, Garvan Institute of Medical Research, Sydney, NSW, Australia
  5. School of Medicine Sydney, University of Notre Dame Australia, Sydney, NSW, Australia

While muscle strength has been associated with fracture risk, the association between muscle performance (a component of sarcopenia) and fracture risk is unclear.  We aimed to assess the contribution of muscle strength and performance to fracture risk and to quantify their ability to improve the Garvan fracture risk calculator’s (GFRC) predictive accuracy.

The study involved 914 women and 505 men (60+years) from Dubbo Osteoporosis Epidemiology Study. Fragility fractures were ascertained by X-ray reports (2000-2018).  Clinical data, BMD, quadriceps strength (QS), timed get-up-and-go (TGUG), five repeated sit-to-stand (5xSTS), and gait speed (GS) were measured biannually. Fracture risk was assessed by Cox’s models adjusted for GFRC predictors (BMD, prior fractures, falls and age). Net reclassification index (NRI) quantified the proportion of cases (fractures) and controls (no-fractures) re-classified to appropriate risk category after the addition of muscle tests to GFRC.

There were 271 and 86 incident fractures over 9,436 and 5,150 person-years in women and men, respectively. In women, neither muscle strength nor performance contributed to fracture risk. However, in men, the worst quartiles of all tests were significantly associated with 2 to 3-fold increase in fracture risk independent of GFRC predictors. The incorporation of muscle strength and performance to GFRC improved the AUC in men by 4-8%. Performance but not strength tests also demonstrated a significant improvement in the reclassification of fracture cases. 5xSTS was associated with the greatest improvement with an NRI of 27% (95% CI: 11%-46%). TGUG and GS were associated with smaller but still significant improvement in NRI.

In summary, in men, muscle strength and performance measurements were significantly associated with fracture risk and the performance tests improved the GFRC predictive accuracy. These data suggest that muscle performance should be incorporated into fracture risk calculation for men.