Publication
Article
The American Journal of Managed Care
Author(s):
Differences in bone density and FRAX fracture risk scores among Black and Asian women yield greater discordance in fracture risk estimation compared with White women.
ABSTRACT
Objectives: Bone mineral density (BMD) and fracture risk calculators (eg, the Fracture Risk Assessment Tool [FRAX]) guide primary prevention care in postmenopausal women. BMD scores use non-Hispanic White (NHW) reference data for T-score classification, whereas FRAX incorporates BMD, clinical risk factors, and population differences when calculating risk. This study compares findings among Asian, Black, and NHW women who underwent osteoporosis screening in a US health care system.
Study Design: Retrospective cross-sectional study.
Methods: Asian, Black, and NHW women aged 65 to 75 years who underwent BMD testing (with no recent fracture, osteoporosis therapy, metastatic cancer, multiple myeloma, metabolic bone disorders, or kidney replacement therapy) were compared across the following measures: femoral neck BMD (FN-BMD) T-score (normal ≥ –1, osteoporosis ≤ –2.5), high FRAX 10-year hip fracture risk (FRAX-Hip ≥ 3%), FRAX risk factors, and diabetes status.
Results: Among 3640 Asian women, 23.8% had osteoporosis and 8.7% had FRAX-Hip scores of at least 3% (34.5% among those with osteoporosis). Among 11,711 NHW women, 12.3% had osteoporosis and 17.2% had FRAX-Hip scores of at least 3% (84.8% among those with osteoporosis). Among 1711 Black women, 68.1% had normal FN-BMD, 4.1% had BMD-defined osteoporosis, and 1.8% had FRAX-Hip scores of at least 3% (32.4% among those with osteoporosis). Fracture risk factors differed by group. Diabetes was 2-fold more prevalent in Black and Asian (35% and 36%, respectively) vs NHW (16%) women.
Conclusions: A large subset of Asian women have discordant BMD and FRAX scores, presenting challenges in osteoporosis management. Furthermore, FN-BMD and especially FRAX scores identified few Black women at high fracture risk warranting treatment. Studies should examine whether fracture risk assessment can be optimized in understudied racial minority populations, particularly when findings are discordant.
Am J Manag Care. 2024;30(3):140-144. https://doi.org/10.37765/ajmc.2024.89515
Takeaway Points
Bone density, Fracture Risk Assessment Tool (FRAX)–defined hip fracture risk, and their relationship differ by race among US women aged 65 to 75 years screened for osteoporosis.
Osteoporosis screening by bone mineral density (BMD) testing is a quality metric for older women.1 The BMD T-score compares a woman’s BMD with peak BMD in a reference population, with guidelines recommending the young adult non-Hispanic White (NHW) female reference for all women.2 The BMD report can include findings from the Fracture Risk Assessment Tool (FRAX) calculator that incorporates age, race and ethnicity, clinical risk factors, and BMD to estimate 10-year probabilities of hip and major osteoporotic fracture. Primary prevention guidelines recommend pharmacologic therapy for postmenopausal women with BMD-defined osteoporosis and those with low bone mass and a high FRAX score.3 To account for known racial and ethnic variation in fracture risk,4,5 the US FRAX includes calibration factors for Black, Asian, and Hispanic race and ethnicity (0.43-0.53) based on epidemiologic studies demonstrating their much lower incidence of hip fracture compared with NHW women.6 This approach reduces potential overestimation of fracture risk,4,5 especially relevant for populations with lower BMD but lower fracture risk.7
To date, our understanding of skeletal health and fracture risk in US racial minority populations remains limited.8 Few studies have examined clinical BMD and FRAX results that inform care for those with lower (Asian women) or higher (Black women) BMD than NHW women. As the fastest-growing US racial group,9 Asian women represent an increasing subset undergoing BMD assessment. Their lower (areal) BMD10,11 is attributable partly to smaller bone size, and studies consistently demonstrate lower hip fracture incidence among US Asian women compared with NHW women.12,13 Black women represent another understudied population, with higher BMD14,15 and lower hip fracture incidence12,13,16 than NHW women. Optimizing fracture prevention in non-White populations is essential for personalizing effective intervention strategies.
As the US population becomes increasingly diverse,9 identifying knowledge gaps in fracture prevention care relevant to real-world populations is paramount. Using contemporary data from a western US population of women undergoing routine osteoporosis screening at the age target of 65 to 75 years,1 we examined femoral neck BMD (FN-BMD) and FRAX scores to characterize the discordance in fracture risk–based scores among Asian, Black, and NHW women.
METHODS
Kaiser Permanente Northern California (KPNC) is a large integrated health care delivery system that has championed osteoporosis screening among older women for more than 20 years. This report examines Asian, Black, and NHW women aged 65 to 75 years with at least 2 years of KPNC membership and initial BMD testing (2016-2017) on a Hologic densitometer who did not have recent fracture, osteoporosis therapy, metastatic cancer, multiple myeloma, metabolic bone disorders, or kidney replacement therapy, as previously described.10 BMDs for Asian and NHW women were reported in a larger study.10 This study was approved by the KPNC Institutional Review Board, with a waiver of informed consent.
Self-reported race and ethnicity were determined from health record/administrative databases, concordant with race and ethnicity in BMD records. Height, weight, body mass index (BMI), FN-BMD, FRAX 10-year probability of hip fracture (FRAX-Hip), and FRAX risk factors (prior fracture, parental hip fracture history, smoking, alcohol ≥ 3 units/day, rheumatoid arthritis, glucocorticoid therapy, and secondary osteoporosis conditions) were obtained from BMD data. Diabetes was defined by at least 2 outpatient or problem-list diagnoses or at least 1 diagnosis with diabetes pharmacotherapy within 2 years prior to BMD testing.
FN-BMD T-score using the Third National Health and Nutrition Examination Survey (1988-1994) young adult NHW female BMD reference (mean [SD], 0.849 [0.111] g/cm2) for Hologic densitometers17 was classified as normal (≥ –1.0), low bone mass or osteopenia (<–1 to >–2.5), or osteoporosis (≤ –2.5).2,17 For Black women, non-Hispanic Black female reference (mean [SD], 0.951 [0.142] g/cm2)17 T-scores were also calculated, consistent with an earlier era.18
Groups were compared using Student t test or Wilcoxon rank sum test and χ2 or Fisher exact tests. Analyses were performed using SAS 9.4 (SAS Institute Inc).
RESULTS
The cohort comprised 3640 Asian women, 1711 Black women, and 11,711 NHW women aged 65 to 75 years. Compared with NHW women, Black women were slightly older and more likely to have higher body weight (mean +7 kg), obesity, and rheumatoid arthritis, and to currently smoke but less likely to have prior fracture or parental hip fracture history (Table). Asian women had lower height (mean –7 cm)10 and body weight (mean –16 kg) and were less likely to smoke and have obesity, prior fracture, or parental hip fracture history compared with NHW women. Diabetes prevalence was more than 2-fold higher among Black (34.7%) and Asian (36.3%) women compared with NHW women (16.0%).
FN-BMD T-scores were higher for Black women but lower for Asian vs NHW women (Table). T-score differences (median 0.4 units lower) for Asian women yielded a 2-fold higher prevalence of FN osteoporosis compared with NHW women (23.8% vs 12.3%), whereas T-score differences (median 0.8 units higher) for Black women yielded a 3-fold lower prevalence of FN osteoporosis (4.1% vs 12.3%). Differences between Black and NHW women were partly attenuated with the young adult Black female reference for FN-BMD T-score in Black women (6.8% vs 12.3%). Only 1.8% of Black women had FRAX-Hip scores of at least 3% (treatment threshold),3 whereas the proportion of Asian women with FRAX-Hip scores of at least 3% (8.7%) was half that of NHW women (17.2%). Most Black women (89.3%) had FRAX-Hip scores below 1% compared with 43.8% of NHW women, pointing to large differences in risk assignment by BMD and especially FRAX compared with NHW women.
Because higher BMI is associated with higher BMD and because BMI differs by race, we compared findings by obesity status (BMI ≥ 30 kg/m2). In each racial group, proportions with BMD-osteoporosis and high FRAX-Hip scores (≥ 3%) were lower for those with vs without obesity (P < .01), and racial differences persisted regardless of weight status (Table). Women with diabetes were more likely to have obesity, higher BMD, and lower FRAX scores than women without diabetes (P < .01).
The Figure compares FRAX-Hip score by FN-BMD T-score categories. Both Asian and Black women with T-scores of –2.0 to –2.4 had very low proportions with FRAX-Hip scores of 3% or higher (2.2% and 4.3%, respectively) compared with NHW women (29.7%). For T-scores of –2.5 to –3.0 (17.1% of Asian women, 9.4% of NHW women, and 3.4% of Black women), the proportion with FRAX-Hip scores of 3% or higher remained much lower for Asian (14.6%) and Black (25.9%) vs NHW (80.2%) women. These findings reflect lower (calibrated) FRAX scores for Asian and Black women at every BMD level, yielding differences in BMD-osteoporosis and FRAX risk assignment by race. Among all women with FN-BMD osteoporosis (T-score ≤ –2.5), 34.5%, 32.4%, and 84.8% of Asian, Black, and NHW women, respectively, had FRAX-Hip scores of 3% or higher.
DISCUSSION
Among Asian and Black women aged 65 to 75 years, there were large differences in BMD and FRAX compared with NHW women and expected within-group discordance. Although lower BMD in Asian women and higher BMD in Black women are well established in epidemiologic studies7,10,11,14,16 and greater BMD-FRAX differences result from US FRAX calibration for these groups,5,6 our findings point to challenges in caring for diverse populations and the potential limitations of FRAX with respect to race. Two-thirds of Black women had normal FN BMD, only 4.1% had FN osteoporosis, and even fewer (1.8%) had FRAX-Hip scores of 3% or higher. Hence, few Black women were identified with high fracture risk warranting treatment, even among those with relatively low BMD for this population. Although low FRAX scores reflected higher BMD, higher BMI, FRAX risk factors, and FRAX calibration, the accuracy of FRAX in identifying Black women at high fracture risk remains understudied. In contrast, 12.3% of NHW women had BMD-osteoporosis, and 17.2% had FRAX-Hip scores of at least 3%, whereas most (85%) with BMD-osteoporosis had FRAX-Hip scores of at least 3%. Finally, Asian women had a 2-fold greater prevalence of FN osteoporosis (23.8%), but only 8.7% had FRAX-Hip scores of at least 3%, including approximately one-third (34%) among those with BMD-osteoporosis. For Asian women, FRAX calibration helps account for lower hip fracture risk despite lower BMD (expected discordance), but guidelines recommend treatment of BMD-osteoporosis in Asian women and do not address their smaller bone size, which contributes to lower areal BMD and overestimation of osteoporosis.7,10,11
Evidence-based guidance is necessary when counseling Asian women with BMD-osteoporosis. Their lower areal BMD is balanced by lower (calibrated) FRAX scores that reduce fracture risk overestimation. Hence, among Asian women aged 65 to 75 years with T-scores of –2.5 to –3.0, only 1 in 7 had FRAX-Hip scores of at least 3% compared with 4 in 5 NHW women. Ethnic T-scores,3 although contrary to guideline recommendations,2 may reduce overestimation of osteoporosis among Chinese women in the US7,11 and increase osteoporosis prevalence among Black women. However, the US Asian population is heterogeneous, and generational differences exist. In an earlier era, ethnic T-scores identified Black women in the US with relatively low BMD using a young adult US Black reference population.18
Use of race- and ethnicity-based calibration factors is debated,4,5,19,20 especially for Black women who have higher BMD than NHW women14,15 and lower hip fracture incidence.12,13 Avoiding risk overestimation in populations with lower fracture incidence is necessary, but underestimation is a concern if higher BMD and other risk factors contribute to the lower observed fracture incidence used to derive calibration factors.
A 2008 survey in the southern US found that only 7% of Black women (vs 56% of White women) aged 65 to 74 years had FRAX-Hip scores of at least 3% using FRAX with BMI (no BMD).21 FRAX classified most Black women below the 3% treatment threshold until age 75 years, suggesting its low utility for identifying Black women younger than 75 years at high fracture risk.21 Among 3484 White and 1041 Black women in Alabama, Georgia, and Iowa with BMD testing, Black women were more likely to have normal BMD than White women (44.7% vs 20.9%, respectively) and less likely to have BMD-osteoporosis (11.6% vs 21.7%), and similar to our study, only 0.3% of Black women had high calculated fracture risk vs 23.7% of White women.22 Black women were also less likely to be on guideline-concordant therapy.22 Among Black adults with rheumatoid arthritis, FRAX risk stratified those 70 years and older regardless of weight status but not younger adults with obesity.23 In our study, only 1% of Black women aged 65 to 75 years with obesity had high FRAX scores (or BMD-osteoporosis), indicating potential challenges in fracture risk assessment for this subset. Overall, two-thirds of Black women had normal FN BMD, so follow-up testing might not be indicated for another 10 years. Furthermore, a majority among the 4.1% of Black women with BMD-osteoporosis had FRAX-Hip scores below the treatment threshold; this larger discordance could potentially contribute to undertreatment despite low BMD. These findings are important to consider because despite higher BMD and lower fracture risk, Black women experience higher morbidity and mortality after major osteoporotic fracture.24,25
FRAX performance is also limited in populations with diabetes,26 which affected approximately one-third of Asian and Black women in our study. Findings from a study conducted in Manitoba, Canada, demonstrate improved fracture risk prediction when diabetes is included as a rheumatoid arthritis risk equivalent in FRAX prediction,26 supporting the need for similar studies in non-White populations.5,26,27 Women with diabetes have higher BMI (contributing to both higher BMD and lower FRAX scores), but high BMI can paradoxically contribute to limb fracture risk,13,28,29 highlighting the complexity of fracture risk estimation in adults with diabetes and obesity. More research is needed among ethnically diverse populations to optimize fracture risk prediction.8
Strengths and Limitations
Our study from California, a state with a high diversity index,9 is the first to our knowledge to examine BMD and FRAX among contemporary Black women in the western US compared with NHW and Asian women in the same health care setting. We specifically chose women aged 65 to 75 years to reflect age targets for the Healthcare Effectiveness Data and Information Set Osteoporosis Screening in Older Women metric.1 Although study limitations include the lack of fracture outcome data (to examine FRAX calibration and accuracy)8,19 and relevant biologic and social factors, these BMD and FRAX findings from real-world practice underscore the need for more research. Importantly, we recognize the limitations of race, a social construct that often includes a range of cultural and social determinants of health and does not account for social and genetic heterogeneity within and among groups. Our study lacked information on nativity, ancestry, and African admixture.30 Nonetheless, awareness of clinical data from risk assessment tools and their potential impact on fracture prevention care in non-White populations is necessary.
CONCLUSIONS
Our observations may inform efforts to optimize fracture risk assessment among diverse populations. Our findings are timely because future updates to FRAX are planned, including pooled analyses that may support ethnicity-specific risk considerations.31 A deeper understanding of skeletal health among racial and ethnic minority populations will support health equity for all women at high risk for fracture.
Acknowledgments
The authors would like to thank Uzoezi Ozomaro, MD, PhD, for her insightful review and editorial suggestions during final manuscript revisions.
Author Affiliations: Division of Research, Kaiser Permanente Northern California (JCL, MC, CL), Oakland, CA; The Permanente Medical Group (JCL, WY, NT, CL, MR, MK, AW), Oakland, CA; Department of Endocrinology, Kaiser Permanente San Jose Medical Center (WY), San Jose, CA; Department of Medicine, Kaiser Permanente Oakland Medical Center (NT), Oakland, CA; Department of Nuclear Medicine, Kaiser Permanente Walnut Creek Medical Center (MR), Walnut Creek, CA; Department of Endocrinology, Kaiser Permanente Santa Clara Medical Center (MK), Santa Clara, CA; Department of Endocrinology, Kaiser Permanente San Francisco Medical Center (AW), San Francisco, CA.
Source of Funding: Research reported in this publication was supported in part by Kaiser Permanente Northern California Community Health and the National Institute on Aging of the National Institutes of Health (R01AG069992). The content is solely the responsibility of the authors and does not represent the official viewpoints of Kaiser Permanente or the National Institutes of Health. The sponsors had no role in the study concept or design, subject or data acquisition, data analysis and interpretation, or manuscript preparation.
Prior Presentation: Some of these data were presented at the American Geriatrics Society Annual Scientific Meeting, May 12-14, 2022, in Orlando, Florida.
Author Disclosures: The authors report no relationship or financial interest with any entity that would pose a conflict of interest with the subject matter of this article.
Authorship Information: Concept and design (JCL, WY, NT, CL, MR, MK); acquisition of data (MC); analysis and interpretation of data (JCL, MC, WY, NT, CL, MR, MK, AW); drafting of the manuscript (JCL, WY, AW); critical revision of the manuscript for important intellectual content (JCL, WY, NT, CL, MR, MK, AW); statistical analysis (MC, CL); provision of patients or study materials (JCL, MR); obtaining funding (JCL, CL); administrative, technical, or logistic support (JCL); and supervision (JCL).
Address Correspondence to: Joan C. Lo, MD, Kaiser Permanente Division of Research, 2000 Broadway, Oakland, CA 94612. Email: Joan.C.Lo@kp.org.
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