JBMR
ORIGINAL ARTICLE
The Importance of Previous Fracture Site on Osteoporosis Diagnosis and Incident Fractures in Women Suzanne N Morin,1 Lisa M Lix,2 and William D Leslie3 1
Department of Medicine, McGill University, Montréal, QC, Canada Department of Community Health Sciences, University of Manitoba, Winnipeg, MB, Canada 3 Department of Internal Medicine, University of Manitoba, Winnipeg, MB, Canada 2
ABSTRACT Previous fracture increases the risk of subsequent fractures regardless of the site of the initial fracture. Fracture risk assessment tools have been developed to guide clinical management; however, no discrimination is made as to the site of the prior fracture. Our objective was to determine which sites of previous nontraumatic fractures are most strongly associated with a diagnosis of osteoporosis, defined by a bone mineral density (BMD) T‐score of 2.5 at the femoral neck, and an incident major osteoporotic fracture. Using administrative health databases, we conducted a retrospective historical cohort study of 39,991women age 45 years and older who had BMD testing with dual‐energy X‐ray absorptiometry (DXA). Logistic regression and Cox proportional multivariate models were used to test the association of previous fracture site with risk of osteoporosis and incident fractures. Clinical fractures at the following sites were strongly and independently associated with higher risk of an osteoporotic femoral neck T‐score after adjustment for age: hip (odds ratio [OR], 3.58; 95% confidence interval [CI], 3.04–4.21), pelvis (OR, 2.23; 95% CI, 1.66–3.0), spine (OR, 2.16; 95% CI, 1.77–2.62), and humerus (OR, 1.74; 95% CI, 1.49–2.02). Cox proportional hazards models, with adjustment for age and femoral neck BMD, showed the greatest increase in risk for a major osteoporotic fracture for women who had sustained previous fractures of the spine (hazard ratio [HR], 2.08; 95% CI, 1.72–2.53), humerus (HR, 1.70; 95% CI, 1.44–2.01), patella (HR, 1.54; 95% CI, 1.10– 2.18), and pelvis (HR, 1.45; 95% CI, 1.04–2.02). In summary, our results confirm that nontraumatic fractures in women are associated with osteoporosis at the femoral neck and that the site of previous fracture impacts on future osteoporotic fracture risk, independent of BMD. © 2014 American Society for Bone and Mineral Research. KEY WORDS: BONE MINERAL DENSITY; FRACTURES; OSTEOPOROSIS; WOMEN; POPULATION‐BASED STUDY
Introduction
O
steoporosis is characterized by low bone mineral density (BMD) and an increased risk for fracture.(1) The aim of osteoporosis management is to identify individuals at high risk for fractures and institute preventative measures, which may include pharmacological therapy.(2) To predict fracture risk accurately in clinical practice is difficult, because osteoporosis is a multifactorial disease, and the estimation of fracture risk depends on the number and nature of risk factors present in each individual. It is well recognized that a previous fracture increases the risk of subsequent fractures, although some sites, like the hip, the vertebra, and the humerus, are associated with a higher risk of subsequent fracture than others.(3) Fracture risk assessment models have been developed to guide clinical management. The Fracture Risk Assessment tool (FRAX), developed by the World Health Organization (WHO), incorporates 10 independent risk factors, such as age, gender, body mass index, and previous low‐trauma fracture, to estimate 10‐year fracture probability.(4) Based on economic models, clinical guidelines recommend treating individuals at high risk of
fractures, such as those with a previous fracture.(5,6) However, in FRAX and other fracture risk algorithms,(7,8) no discrimination is made as to the site of previous fractures when one enters an individual’s data into the assessment tool. Consequently, clinicians might not appreciate the relative importance of different fracture sites as risk factors for recurrent fractures. Our aim was to determine which sites of previous fracture were most strongly associated with a diagnosis of osteoporosis as defined by a femoral neck BMD T‐score of 2.5, and with an incident major osteoporotic fracture.
Subjects and Methods Study design and population Using comprehensive health care databases of the Province of Manitoba in Canada (population 1.2 million in 2005), we designed a historical cohort study of women aged 45 years and older who underwent baseline clinical BMD testing for evaluation of fracture risk from 1990 to 2007. Virtually all citizens of the province of Manitoba have universal access to publicly
Received in original form November 8, 2013; revised form February 6, 2014; accepted February 9, 2014. Accepted manuscript online February 18, 2014. Address correspondence to: Suzanne N Morin, MD, MSc, McGill University Health Center, 1650 Cedar Ave, Room B2‐118, Montréal, Québec, H3G 1A4, Canada. E‐mail: [email protected] Journal of Bone and Mineral Research, Vol. 29, No. 7, July 2014, pp 1675–1680 DOI: 10.1002/jbmr.2204 © 2014 American Society for Bone and Mineral Research
1675
funded medical care including BMD testing. The Manitoba Bone Density Program is a unique integrated program that manages all clinical dual‐energy X‐ray absorptiometry (DXA) testing of the province.(9) Criteria for testing are consistent with published guidelines (www.gov.mb.ca/health/programs/mbd). DXA testing rates for this program have been published and the program’s database has been shown to be over 99% complete and accurate.(9,10) The Manitoba Bone Density Program database can be linked with provincial computerized health databases (hospital discharge summary, physician claims and province‐ wide pharmacy databases) through an anonymous personal identifier. The accuracy of these databases for fracture outcomes research has been well validated.(11,12) We identified all women age 45 years and older with a first femoral neck BMD measurement between January 1, 1990 and March 31, 2007. All women had continuous medical coverage from Manitoba Health during the observation period. For women with more than one eligible set of BMD measurements, only the first record was included. The study was approved by the Research Ethics Board for the University of Manitoba and the Health Information Privacy Committee of Manitoba Health.
Bone density measurement Prior to 2000, DXA measurements were performed with a pencil‐ beam instrument (Lunar DPX; GE Lunar, Madison WI, USA) and after this date a fan‐beam instrument was used (Lunar Prodigy; GE Lunar). Densitometers showed stable long‐term performance (coefficient of variation [CV]
ORIGINAL ARTICLE
The Importance of Previous Fracture Site on Osteoporosis Diagnosis and Incident Fractures in Women Suzanne N Morin,1 Lisa M Lix,2 and William D Leslie3 1
Department of Medicine, McGill University, Montréal, QC, Canada Department of Community Health Sciences, University of Manitoba, Winnipeg, MB, Canada 3 Department of Internal Medicine, University of Manitoba, Winnipeg, MB, Canada 2
ABSTRACT Previous fracture increases the risk of subsequent fractures regardless of the site of the initial fracture. Fracture risk assessment tools have been developed to guide clinical management; however, no discrimination is made as to the site of the prior fracture. Our objective was to determine which sites of previous nontraumatic fractures are most strongly associated with a diagnosis of osteoporosis, defined by a bone mineral density (BMD) T‐score of 2.5 at the femoral neck, and an incident major osteoporotic fracture. Using administrative health databases, we conducted a retrospective historical cohort study of 39,991women age 45 years and older who had BMD testing with dual‐energy X‐ray absorptiometry (DXA). Logistic regression and Cox proportional multivariate models were used to test the association of previous fracture site with risk of osteoporosis and incident fractures. Clinical fractures at the following sites were strongly and independently associated with higher risk of an osteoporotic femoral neck T‐score after adjustment for age: hip (odds ratio [OR], 3.58; 95% confidence interval [CI], 3.04–4.21), pelvis (OR, 2.23; 95% CI, 1.66–3.0), spine (OR, 2.16; 95% CI, 1.77–2.62), and humerus (OR, 1.74; 95% CI, 1.49–2.02). Cox proportional hazards models, with adjustment for age and femoral neck BMD, showed the greatest increase in risk for a major osteoporotic fracture for women who had sustained previous fractures of the spine (hazard ratio [HR], 2.08; 95% CI, 1.72–2.53), humerus (HR, 1.70; 95% CI, 1.44–2.01), patella (HR, 1.54; 95% CI, 1.10– 2.18), and pelvis (HR, 1.45; 95% CI, 1.04–2.02). In summary, our results confirm that nontraumatic fractures in women are associated with osteoporosis at the femoral neck and that the site of previous fracture impacts on future osteoporotic fracture risk, independent of BMD. © 2014 American Society for Bone and Mineral Research. KEY WORDS: BONE MINERAL DENSITY; FRACTURES; OSTEOPOROSIS; WOMEN; POPULATION‐BASED STUDY
Introduction
O
steoporosis is characterized by low bone mineral density (BMD) and an increased risk for fracture.(1) The aim of osteoporosis management is to identify individuals at high risk for fractures and institute preventative measures, which may include pharmacological therapy.(2) To predict fracture risk accurately in clinical practice is difficult, because osteoporosis is a multifactorial disease, and the estimation of fracture risk depends on the number and nature of risk factors present in each individual. It is well recognized that a previous fracture increases the risk of subsequent fractures, although some sites, like the hip, the vertebra, and the humerus, are associated with a higher risk of subsequent fracture than others.(3) Fracture risk assessment models have been developed to guide clinical management. The Fracture Risk Assessment tool (FRAX), developed by the World Health Organization (WHO), incorporates 10 independent risk factors, such as age, gender, body mass index, and previous low‐trauma fracture, to estimate 10‐year fracture probability.(4) Based on economic models, clinical guidelines recommend treating individuals at high risk of
fractures, such as those with a previous fracture.(5,6) However, in FRAX and other fracture risk algorithms,(7,8) no discrimination is made as to the site of previous fractures when one enters an individual’s data into the assessment tool. Consequently, clinicians might not appreciate the relative importance of different fracture sites as risk factors for recurrent fractures. Our aim was to determine which sites of previous fracture were most strongly associated with a diagnosis of osteoporosis as defined by a femoral neck BMD T‐score of 2.5, and with an incident major osteoporotic fracture.
Subjects and Methods Study design and population Using comprehensive health care databases of the Province of Manitoba in Canada (population 1.2 million in 2005), we designed a historical cohort study of women aged 45 years and older who underwent baseline clinical BMD testing for evaluation of fracture risk from 1990 to 2007. Virtually all citizens of the province of Manitoba have universal access to publicly
Received in original form November 8, 2013; revised form February 6, 2014; accepted February 9, 2014. Accepted manuscript online February 18, 2014. Address correspondence to: Suzanne N Morin, MD, MSc, McGill University Health Center, 1650 Cedar Ave, Room B2‐118, Montréal, Québec, H3G 1A4, Canada. E‐mail: [email protected] Journal of Bone and Mineral Research, Vol. 29, No. 7, July 2014, pp 1675–1680 DOI: 10.1002/jbmr.2204 © 2014 American Society for Bone and Mineral Research
1675
funded medical care including BMD testing. The Manitoba Bone Density Program is a unique integrated program that manages all clinical dual‐energy X‐ray absorptiometry (DXA) testing of the province.(9) Criteria for testing are consistent with published guidelines (www.gov.mb.ca/health/programs/mbd). DXA testing rates for this program have been published and the program’s database has been shown to be over 99% complete and accurate.(9,10) The Manitoba Bone Density Program database can be linked with provincial computerized health databases (hospital discharge summary, physician claims and province‐ wide pharmacy databases) through an anonymous personal identifier. The accuracy of these databases for fracture outcomes research has been well validated.(11,12) We identified all women age 45 years and older with a first femoral neck BMD measurement between January 1, 1990 and March 31, 2007. All women had continuous medical coverage from Manitoba Health during the observation period. For women with more than one eligible set of BMD measurements, only the first record was included. The study was approved by the Research Ethics Board for the University of Manitoba and the Health Information Privacy Committee of Manitoba Health.
Bone density measurement Prior to 2000, DXA measurements were performed with a pencil‐ beam instrument (Lunar DPX; GE Lunar, Madison WI, USA) and after this date a fan‐beam instrument was used (Lunar Prodigy; GE Lunar). Densitometers showed stable long‐term performance (coefficient of variation [CV]
