Bone, Fall Related Risk Factors and Subsequent Fracture Risk
Bone, Fall Related Risk Factors and Subsequent Fracture Risk
The Fracture Liaison Service is a collaboration between the department of surgery, orthopaedics and internal medicine (rheumatology and endocrinology) and is based on the consensus guideline osteoporosis of the Dutch Institute for Health Care Improvement (CBO). The Fracture Liaison Service is coordinated by a specialised and dedicated fracture nurse.
Between September 2004 and September 2006 all consecutive patients older than 50 years with a recent non-vertebral fracture, who entered the level one trauma centre in the south of the Netherlands were invited to participate. Patients with pathological or vertebral fractures or living outside the postal area were excluded. All patients were prospectively followed for two years. The hospital database was searched for radiographically confirmed first and subsequent NVF, fracture location and date of occurrence. All NVFs (baseline and subsequent) were categorised according to International Classification of Disease (ICD)-9 and then pooled into 2 groups: major (hip, pelvis, proximal humerus, proximal tibia, multiple ribs or distal femur fracture), and minor (all other) fractures. All groups were mutually exclusive. First and subsequent fractures were classified according to the main fracture. The national obituary database was searched to investigate whether patients were deceased.
The study was approved by the medical ethical committee of the hospital (MEC 03–194).
All patients, who were able and agreed to evaluate their fracture risk assessment, were invited to attend the Fracture Liaison Service. Medical history, current and past medication use, living situation, conditions concerning the occurrence of the fracture, dietary calcium and vitamin D intake were assessed. Additionally, bone- and fall- related risk factors were systematically assessed, and bone mineral density was measured by dual energy X-ray absorptiometry (DXA, Hologic QDR 4500) at the lumbar spine and femoral neck. Based on criteria of the World Health Organisation osteoporosis was classified as T-score of ≤ −2.5, osteopenia as T-score between −1.0 and −2.5, and normal BMD as T-score of >−1.0.
According to the national osteoporosis guideline the following bone- and fall-related risk factors were evaluated: a history of clinical fracture after the age of 50 years, family history of hip fracture, low body weight (<60 kg), glucocorticoid use and immobility (<4 hours per day). Vertebral fractures were excluded from this study, since the exact date of occurrence is often unclear. Patients were categorised as having a bone-related risk factor if they had osteoporosis or at least one of the above mentioned risk factors.
According to the national guideline on fall prevention the following fall-related risk factors were evaluated: a previous falls in the last 12 months (the fall leading to the current fracture was excluded), the presence of Parkinson's disease, current use of psycho-active medication, urinary incontinence (defined as involuntary loss of urine) and articular complaints. Additionally, the Groningen Activity Restriction Scale (GARS) was used to estimate the disability in activities of daily living (ADL). Patients were categorised as having a fall-related risk factor if at least one of the risk factors mentioned above was present or the GARS showed low ADL.
According to the Dutch guidelines on osteoporosis and fall prevention patients started with Calcium and Vitamin D or a bisphosphonate in the presence of osteoporosis.
For the analyses, patients were categorised into subgroups according to the presence, combination or absence of bone- and fall-related risk factors: (1) patients with only bone-related risk factors, (2) patients with combination of bone- and fall-related risk factors, (3) patients with only fall-related risk factors, and (4) patients without bone- or fall-related risk factors. The rationale behind these groups is that there is a known treatable risk factor in group 1 and 2, but not in group 3 because in fracture prevention only bone targeted therapy has shown to reduce fracture risk and not fall targeted therapies.
Differences between the groups were analysed using the chi-square or Fisher's exact test for categorical variables. ANOVA and independent samples t-test for numerical variables. Kaplan-Meier and multivariable Cox regression analyses were performed using subsequent fracture and mortality as dependent variables (events), adjusted for age, sex and baseline fracture location (major/minor). For subsequent fracture as dependent variable, follow-up time started at time of current fracture (time = 0) and was defined as time between current fracture and subsequent fracture (= event), death or end of 2-year follow-up period (= censored). For mortality, follow-up time was calculated as time between current fracture and death (= event) or end of 2-year follow-up period (= censored). Schoenfeld residuals were used to check the proportional hazards assumption and, if violated, time-dependent Cox regression was used. Linearity was checked for continuous variables and, if violated, centered quadratic terms were included. A two-sided p-value ≤ 0.05 was considered statistically significant. All analyses were performed using SPSS for Mac (version 18.0.0; SPSS Inc., Illinois, USA).
Methods
Study Design
The Fracture Liaison Service is a collaboration between the department of surgery, orthopaedics and internal medicine (rheumatology and endocrinology) and is based on the consensus guideline osteoporosis of the Dutch Institute for Health Care Improvement (CBO). The Fracture Liaison Service is coordinated by a specialised and dedicated fracture nurse.
Between September 2004 and September 2006 all consecutive patients older than 50 years with a recent non-vertebral fracture, who entered the level one trauma centre in the south of the Netherlands were invited to participate. Patients with pathological or vertebral fractures or living outside the postal area were excluded. All patients were prospectively followed for two years. The hospital database was searched for radiographically confirmed first and subsequent NVF, fracture location and date of occurrence. All NVFs (baseline and subsequent) were categorised according to International Classification of Disease (ICD)-9 and then pooled into 2 groups: major (hip, pelvis, proximal humerus, proximal tibia, multiple ribs or distal femur fracture), and minor (all other) fractures. All groups were mutually exclusive. First and subsequent fractures were classified according to the main fracture. The national obituary database was searched to investigate whether patients were deceased.
The study was approved by the medical ethical committee of the hospital (MEC 03–194).
Measurements
All patients, who were able and agreed to evaluate their fracture risk assessment, were invited to attend the Fracture Liaison Service. Medical history, current and past medication use, living situation, conditions concerning the occurrence of the fracture, dietary calcium and vitamin D intake were assessed. Additionally, bone- and fall- related risk factors were systematically assessed, and bone mineral density was measured by dual energy X-ray absorptiometry (DXA, Hologic QDR 4500) at the lumbar spine and femoral neck. Based on criteria of the World Health Organisation osteoporosis was classified as T-score of ≤ −2.5, osteopenia as T-score between −1.0 and −2.5, and normal BMD as T-score of >−1.0.
According to the national osteoporosis guideline the following bone- and fall-related risk factors were evaluated: a history of clinical fracture after the age of 50 years, family history of hip fracture, low body weight (<60 kg), glucocorticoid use and immobility (<4 hours per day). Vertebral fractures were excluded from this study, since the exact date of occurrence is often unclear. Patients were categorised as having a bone-related risk factor if they had osteoporosis or at least one of the above mentioned risk factors.
According to the national guideline on fall prevention the following fall-related risk factors were evaluated: a previous falls in the last 12 months (the fall leading to the current fracture was excluded), the presence of Parkinson's disease, current use of psycho-active medication, urinary incontinence (defined as involuntary loss of urine) and articular complaints. Additionally, the Groningen Activity Restriction Scale (GARS) was used to estimate the disability in activities of daily living (ADL). Patients were categorised as having a fall-related risk factor if at least one of the risk factors mentioned above was present or the GARS showed low ADL.
According to the Dutch guidelines on osteoporosis and fall prevention patients started with Calcium and Vitamin D or a bisphosphonate in the presence of osteoporosis.
For the analyses, patients were categorised into subgroups according to the presence, combination or absence of bone- and fall-related risk factors: (1) patients with only bone-related risk factors, (2) patients with combination of bone- and fall-related risk factors, (3) patients with only fall-related risk factors, and (4) patients without bone- or fall-related risk factors. The rationale behind these groups is that there is a known treatable risk factor in group 1 and 2, but not in group 3 because in fracture prevention only bone targeted therapy has shown to reduce fracture risk and not fall targeted therapies.
Statistical Analysis
Differences between the groups were analysed using the chi-square or Fisher's exact test for categorical variables. ANOVA and independent samples t-test for numerical variables. Kaplan-Meier and multivariable Cox regression analyses were performed using subsequent fracture and mortality as dependent variables (events), adjusted for age, sex and baseline fracture location (major/minor). For subsequent fracture as dependent variable, follow-up time started at time of current fracture (time = 0) and was defined as time between current fracture and subsequent fracture (= event), death or end of 2-year follow-up period (= censored). For mortality, follow-up time was calculated as time between current fracture and death (= event) or end of 2-year follow-up period (= censored). Schoenfeld residuals were used to check the proportional hazards assumption and, if violated, time-dependent Cox regression was used. Linearity was checked for continuous variables and, if violated, centered quadratic terms were included. A two-sided p-value ≤ 0.05 was considered statistically significant. All analyses were performed using SPSS for Mac (version 18.0.0; SPSS Inc., Illinois, USA).
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