Evaluating The Utility Of Bone Turnover Markers Bap And Ntx In Assessing Musculoskeletal Injury Risk: Nhanes 1999-2002

Bone turnover markers such as bone-specific alkaline phosphatase (BAP) and N-telopeptide of type I collagen (NTx) have been used to gauge musculoskeletal stress resulting from training regimes. NTx and BAP increase acutely in dose-response fashion after novel exercise exposure followed by a gradual return to baseline. Conversely, these markers are suppressed in those exposed to extremely high workloads as well as in those with inflammatory disorders. PURPOSE: As the bone and immune systems share common functional pathways, examining markers of bone turnover could offer valuable insights into musculoskeletal injury risk. Therefore, this study aims to investigate the utility of BAP and NTx in conjunction with other risk factors to assess injury risk in a U.S. population representative sample. METHODS: Data from over 21,000 respondents were collected from the 1999-2002 NHANES cycles. We performed case-control matching followed by principal component analysis (PCA) on risk factors significantly associated with bone/joint injury. Linear regression modeling was performed to determine the predictive value of BAP and NTx for all extracted factors. RESULTS: Significant variables that maximized Kaiser-Meyer-Olkin test (0.55) were entered into the PCA including age, body mass index, physical activity level, physical functioning, muscle strengthening activities, pain, income level, military status, BAP, and NTx. Four components accounting for 60% of the variance in injury incidence were extracted (p < 0.001). NTx and BAP were positively loaded and predictive of component 1 factor scores (r2 = 0.73; p < 0.001) (See figure) which accounted for 18% of the total variance in injury status. Low muscle-strengthening frequency and elevated BMI also loaded onto component 1. CONCLUSIONS: When taken with other factors, bone turnover markers are plausible predictors of bone/injury possibly reflecting sedentary lifestyle and concomitant underlying inflammatory processes.