Racial and Ethnic Differences in Hip Fracture Outcomes in Men
Lucy H. Liu, MD, MPH; Malini Chandra, MS, MBA; Joel R. Gonzalez, MPH, MPP; and Joan C. Lo, MD
The economic burden of hip fractures in the United States is projected to exceed $17 billion by 2025.1 Although declines in hip fracture incidence are evident since the mid-1990s,2-4 the growth and demographic shifts of the aging US population are expected to contribute to an increasing number of hip fractures among older individuals and those of nonwhite race/ethnicity.1,5 Hip fracture rates are substantially higher in women compared with men,2 affecting whites more than blacks, Hispanics, and Asians.6-8 However, men experience greater post-fracture morbidity and mortality,2,3,9-14 even after adjustment for differences in age and prefracture comorbidity.15,16 Men also experience a higher incidence of postoperative complications, such as delirium, congestive heart failure, renal failure, decubitus ulcers, and infections, and are less likely to return to their functional baseline compared with women.14,15,17-20
In 2014, the International Osteoporosis Foundation issued a report on osteoporosis in men, drawing attention to the increasing burden of osteoporosis and fragility fractures as the population of aging men increases, especially in Asia and Latin America.21 This report cited data from the US National Hospital Discharge Survey, estimating a 51.8% increase in hip fractures among men from 2010 to 2030, compared with an expected 3.5% decline in women.4,21 Few studies have examined contemporary trends within diverse integrated healthcare delivery settings. Racial and ethnic population trends in men are also limited, but hip fracture rates appear to be declining among white men, although not necessarily among men of nonwhite race/ethnicity.5,22
Large observational cohorts have established important racial/ethnic differences in mortality outcome following hip fracture, with the majority of data comprising outcomes reported among women.14 Historically, black women experience higher post-fracture mortality compared with white women, despite lower hip fracture rates.6 Within our healthcare system, we found similar mortality risk following hip fracture for black and white women, but lower mortality for Hispanic and Asian women.23 Less is known regarding racial/ethnic disparities in postfracture mortality among men, particularly Asians. This study examines contemporary rates of hip fracture and postfracture mortality in a diverse population of older men, using data from a large integrated healthcare delivery system.
The source population included health plan members of Kaiser Permanente Northern California (KPNC), an integrated healthcare system serving over 3.2 million members, with centralized electronic databases of all outpatient, hospitalization, and administrative records. For these analyses, men 50 years or older with a principal hospital discharge diagnosis of proximal femur fracture (International Classification of Diseases, 9th edition [ICD-9] codes 820.0x, 820.2x, 820.8) during January 1, 2000, to December 31, 2010, were identified, examining the first qualifying fracture per calendar year. Open fractures (ICD-9: 820.1x, 820.3x, 820.9) and those with major trauma (secondary ICD-9: E800-E848) were excluded. This study was approved by the Kaiser Foundation Research Institute Institutional Review Board.
Demographic data were obtained from administrative databases, including self-reported race/ethnicity categorized as non-Hispanic white, non-Hispanic black, Hispanic, Asian, and other (including multiple race) or unknown race/ethnicity. The comorbidity index was calculated using Deyo and colleagues’ modification of the Charlson Comorbidity Index,24 based on diagnosis and procedure codes obtained from hospitalization, emergency, and ambulatory visits during the year prior to hip fracture. All-cause mortality was determined up to 12 months following hip fracture, using health plan and administrative databases (updated with information from state death certificates and Social Security Administration files), as previously described.23 Less than 1% of the study cohort had membership cessation within 1 year post fracture, excluding ascertained death outcomes; these individuals were presumed alive at 1 year.
Comparisons between subgroups were examined by Student’s t test for continuous variables and χ2 test for categorical variables. Hip fracture incidence was examined using age-eligible denominators for each calendar year, with rates adjusted for age using the 2010 US Census standard population data.25 Trends in age-adjusted fracture incidence were examined using generalized estimating equations, as previously described,7 with racial and ethnic differences examined for the final year of observation (2010). Multivariable logistic regression was conducted to examine the independent association of race/ethnicity and 1-year postfracture mortality, adjusting for age and comorbidity index. All analyses were conducted using SAS version 9.3 (SAS Institute; Cary, North Carolina). P <.05 was chosen as the criterion for statistical significance.
From 2000 to 2010, 6247 men 50 years or older experienced a qualifying hip fracture, with a mean age of 79.3 ± 9.8 years at the time of hip fracture; three-fourths (74.5%) were 75 years or older. The demographic distribution included 81.4% white, 7.5% Hispanic, 3.9% Asian, 3.8% black, and 3.6% other/unknown race/ethnicity, similar to KPNC women experiencing hip fracture.7 We found that age at fracture differed slightly by race/ethnicity, with black (mean age of 77.8 ± 9.8 years) and Asian (77.5 ± 10.6 years) men experiencing hip fracture at slightly younger ages compared with white men (79.6 ± 9.8 years; P <.05), but no difference between Hispanic (78.7 ± 9.6 years) and white men.
The average annual age-adjusted incidence of hip fracture during 2000 to 2010 was 127 per 100,000 men, ranging from 116 to 139 per 100,000, although no overall significant trend was observed (Figure 1). Racial/ethnic differences in contemporary hip fracture rates were evident. In 2010, the age-adjusted incidence of hip fracture was highest for white men (137 per 100,000), similar among Hispanic (98 per 100,000) and black (80 per 100,000) men, and lowest in Asian (45 per 100,000) men (P <.01 for all race groups vs white and for Asian vs Hispanic).
Of the 6247 men who experienced a hip fracture during 2000 to 2010, nearly one-third died during the ensuing year. All-cause mortality rates were 11.1%, 19.8%, 25.4%, and 32.9% at 1, 3, 6, and 12 months following hip fracture, respectively. These rates are 1.5-fold higher than mortality rates reported in KPNC women post hip fracture (17.0% at 6 months, 22.8% at 12 months).23 As expected, mortality following hip fracture increased substantially with age (Figure 2 [a]), with lower 1-year mortality in younger, compared with older, men post hip fracture across all age group comparisons (P <.001).
We further examined postfracture mortality rates by race/ethnicity (Figure 2 [b]). Racial and ethnic differences at 1 year (P = .02) were notable for lower 1-year mortality among Asian men (23.1%; P <.05) compared with white (33.7%), black (32.4%), and Hispanic (31.1%) men. However, Asian men were also slightly younger at the time of hip fracture. Adjusting for age, Asian men remained at significantly lower mortality risk compared with white men (adjusted odds ratio [aOR], 0.65; 95% confidence interval [CI], 0.47-0.88), whereas no differences were seen for Hispanic (aOR, 0.93; 95% CI, 0.76-1.15) and black (aOR, 1.05; 95% CI, 0.79-1.15) men compared with white men at 1 year. These results were largely unchanged after additionally adjusting for baseline comorbidity index and calendar year of fracture (aOR, 0.62; 95% CI, 0.45-0.86 for Asian; aOR, 0.88; 95% CI, 0.71-1.09 for Hispanic; aOR, 0.96; 95% CI, 0.71-1.29 for black compared with white men).
Hip fracture remains a major public health issue, contributing substantially to healthcare cost1 and morbidity and mortality of older individuals. Screening guidelines for osteoporosis, a major risk factor for hip fracture, have been well established for older women,26-28 and guidelines are now in place for older men.28-30 However, according to the US Preventive Services Task Force, there is insufficient evidence to evaluate the risks and benefits of osteoporosis screening in men,27 and men are much less likely than women to receive treatment for osteoporosis.31 Even after hip fracture, only a fraction of men receive osteoporosis treatment compared with women.32 Within our health plan, the annual incidence of hip fracture among older men averaged 127 per 100,000, with an incidence of 116 per 100,000 during the final year of observation (2010). These data provide a benchmark for future assessment of fracture trends following implementation of osteoporosis outreach programs for men, similar to earlier outreach programs for women contributing to reductions in hip fracture and subsequent mortality risk.7,23 Kaiser Permanente Southern California reported temporal reductions in hip fracture rates for both men and women,33 attributed to regionwide efforts and establishment of a multidisciplinary osteoporosis management program to aggressively screen and treat patients for osteoporosis.
Given the growing US population, Hispanics and Asians are projected to have the greatest rate of increase in hip fracture costs by 2025,1 underscoring the need to better understand potential disparities in fracture incidence and mortality. In our study, hip fracture rates were highest in white men and lower for other races and ethnicities—similar to findings in women23 and recent data from California.34 Racial and ethnic differences in bone mineral density (BMD) are known, with blacks having higher BMD compared with whites,35,36 accounting in part for lower fracture risk.37 Smaller body size contributes to lower BMD in Asian men,35 although BMD is not the only measure of femur strength given that Asian men also have a lower incidence of fracture compared with white counterparts.38 Differences in femur size, hip geometry (shorter hip axis length in Asians), and/or hip strength indices may also explain ethnic variation in fracture risk,39-41 as well as cultural influences on activity level and fall risk. Within our health plan, 10% of men 65 years or older are Asian,42 whereas only 3.9% of men with hip fracture are Asian. A two-thirds lower age-adjusted incidence of hip fracture was observed in Asian compared with white men.
Although men contribute a much smaller subset of the hip fracture population than women, they suffer greater morbidity and mortality compared with women. In our study, 1-year mortality following hip fracture was 32.9% in men—substantially higher than women (22.8%) within the same healthcare setting.23 National and regional data also demonstrate higher mortality rates up to 1 year post hip fracture in men compared with women.2,34 Because men may be less prone to falls, those who do experience hip fracture may have increased frailty, greater comorbidity, higher susceptibility to medical complications (eg, pneumonia), and potentially lower rates of subsequent bisphosphonate therapy compared with women.18,32,43 Whether the observed gender differences in mortality risk following hip fracture relate to pre- or postfracture health, including a potentially greater contribution of infection-related complications in men,15 is unclear.
Our study contributes to the growing recognition of racial/ethnic differences in postfracture mortality. Similar to women, 1-year mortality rates following hip fracture were lower in Asian men, but mortality rates were comparable for white, black, and Hispanic men. A recent study examining nonfederal hospital admissions for hip fracture–related procedures in California reported more than one-third lower postfracture mortality risk for Asian men and somewhat lower mortality risk among black and Hispanic compared with white men.34 Whether hospital readmission or other postfracture complications,44 as well as ethnic differences in family structure, social support, and use of rehabilitation services,45-48 contribute to these findings is unclear. Contemporary data pertaining to US Asian men also remain limited. Collectively, these findings emphasize the need to further investigate factors underlying the observed ethnic differences in hip fracture outcomes among older men.
Limitations and Strengths
Our study has several limitations. First, we did not examine specific preexisting comorbidities, functional status, osteoporosis risk factors, and treatment, which may differ by race and play an important role in patient outcomes. Second, information on mobility and/or functional independence, discharge to inpatient rehabilitation, body mass index, and nutritional status were not systematically available. Lastly, we were unable to account for population trends in mortality to determine whether the observed racial differences reflect mortality patterns within our health plan population, irrespective of hip fracture.
The strengths of our study include access to an extremely large and diverse population, with comprehensive data on mortality outcomes and hospitalized events. Asians represent one of the fastest growing ethnic subgroups within the United States, among whom a better understanding of hip fracture epidemiology and outcome has become increasingly important. These data are among the first to examine contemporary differences in both hip fracture rates and mortality outcome in men of Asian ethnicity and white race receiving care within the same healthcare delivery system.
We noted important racial/ethnic differences in hip fracture incidence and 1-year mortality outcome following the fracture. Compared with men of white race, Asian men had two-thirds lower hip fracture incidence and one-third lower mortality risk at 1 year following hip fracture. As the aging population becomes increasingly diverse, a greater understanding of the cultural, social, and health-related factors affecting fracture outcomes in healthcare settings will optimize the targeting of multidisciplinary efforts to reduce morbidity and mortality following hip fracture in men.