Fracture risk prediction: importance of age, BMD and spine fracture status

Abstract

Our purpose was to identify factors for a parsimonious fracture risk assessment model considering morphometric spine fracture status, femoral neck bone mineral density (BMD) and the World Health Organization (WHO) clinical risk factors. Using data from 2761 subjects from the Canadian Multicentre Osteoporosis Study (CaMos), a prospective, longitudinal cohort study of randomly selected community-dwelling men and women aged ⩾50 years, we previously reported that a logistic regression model considering age, BMD and spine fracture status provided as much predictive information as a model considering these factors plus the remaining WHO clinical risk factors. The current analysis assesses morphometric vertebral fracture and/or nonvertebral fragility fracture at 5 years using data from an additional 1964 CaMos subjects who have now completed 5 years of follow-up (total N=4725). Vertebral fractures were identified from lateral spine radiographs assessed using quantititative morphometry at baseline and end point. Nonvertebral fragility fractures were determined by questionnaire and confirmed using radiographs or medical records; fragility fracture was defined as occurring with minimal or no trauma. In this analysis, a model including age, BMD and spine fracture status provided a gradient of risk per s.d. (GR/s.d.) of 1.88 and captured most of the predictive information of a model including morphometric spine fracture status, BMD and all WHO clinical risk factors (GR/s.d. 1.92). For comparison, this model provided more information than a model considering BMD and the WHO clinical risk factors (GR/s.d. 1.74). These findings confirm the value of age, BMD and spine fracture status for predicting fracture risk.

Figure 1

Univariate analyses of GR/s.d. for predicting 5-year fracture risk. BMD, femoral neck T-score; VFx, spine fracture status (yes/no); Clin, previous clinical fracture; FH, parental history of hip fracture; Smo, current smoking; GC, systemic glucocorticoids >3 months; RA, rheumatoid arthritis: EtOH, >2 alcoholic drinks/day.

Figure 2

GR/s.d. for models including baseline age, age+femoral neck T-score, age+femoral neck T-score+spine fracture status (yes/no), etc. BMD, femoral neck T-score; VFx, spine fracture status; Clin, previous clinical fracture; FH, parental history of hip fracture; Smo, current smoking; GC,systemic glucocorticoids >3 months; RA, rheumatoid arthritis; EtOH, >2 alcoholic drinks/day.

Figure 3

Predicted 5-year risk of incident fragility fracture in CaMos women based on the logistic regression model with predictors including baseline age, femoral neck T-score and spine fracture status (Yes/No). Shaded symbols with solid lines represent FN T-scores for patients with no prevalent vertebral fractures; open symbols with dashed lines represent FN T-scores for patients with prevalent vertebral fractures. FN, femoral neck; VFx +, prevalent spine fracture; VFx −, no prevalent spine fracture.

Figure 4

Venn diagram showing (a) subjects with prevalent vertebral fractures as assessed by questionnaire versus lateral spine imaging, (b) subjects having >30% 5-year fracture risk as assessed by models considering age, age plus femoral neck BMD (FN BMD) and age plus FN BMD plus spine fracture status (VFx) (yes/no) and (c) subjects having >30% 5-year fracture risk as assessed by models considering age plus FN BMD plus VFx, and age plus FN BMD plus VFx plus previous clinical fracture (Clin) plus the remaining WHO clinical risk factors: parental history of hip fracture (FH) plus current smoking (Smo) plus systemic glucocorticoids >3 months (GC) plus rheumatoid arthritis (RA) plus >2 alcoholic drinks/day (EtOH).