Racial and Ethnic Differences in Hip Fracture Outcomes in Men

ABSTRACT

Objectives: To examine temporal trends and racial/ethnic differences in hip fracture incidence and mortality outcome in older men.

Study Design: Retrospective cohort study.

Methods: We ascertained men 50 years or older with a hip fracture during 2000 to 2010 in a diverse northern California healthcare population. Age, comorbidity index, hip fracture incidence, and all-cause mortality up to 12 months post fracture were examined and compared by race/ethnicity.

Results: A total of 6247 men (aged 79.3 ± 9.8 years) experienced a hip fracture during 2000 to 2010: 81.4% were white, 7.5% Hispanic, 3.8% black, and 3.9% Asian. The age-adjusted annual incidence of hip fracture averaged 127 per 100,000, ranging from 116 to 139 per 100,000 during this period. In 2010, the age-adjusted incidence of hip fracture was highest among white men (137), followed by Hispanic (98) and black (80), and was lowest among Asian men (45 per 100,000). Mortality following hip fracture was 11.1%, 19.8%, 25.4%, and 32.9%, within 1, 3, 6, and 12 months, respectively, and increased with age. One-year mortality was similar for whites (33.7%), blacks (32.4%), and Hispanics (31.1%), but lower for Asians (23.1%; P <.05). Adjusting for age, comorbidity index, and calendar year, Asians remained at lower mortality risk compared with whites (adjusted odds ratio, 0.62; 95% confidence interval, 0.45-0.86).

Conclusions: Although hip fracture rates were largely stable among older men, contemporary rates of hip fracture were highest for white and lowest for Asian men. One-year mortality was similar for white, black, and Hispanic men, but significantly lower for Asians. Future studies should investigate factors underlying observed ethnic differences in fracture outcome among US men.

Am J Manag Care. 2017;23(9):560-564Takeaway Points

Within an integrated healthcare delivery system, overall hip fracture rates were stable in older men, but important racial and ethnic differences in the incidence of hip fracture and subsequent 1-year mortality following hip fracture were observed.

• The incidence of hip fracture was highest among white men, lower among Hispanic and black men, and lowest among Asian men.
• Compared with white men and adjusting for age, comorbidity burden, and fracture year, Asian men experienced lower 1-year mortality risk following hip fracture, whereas differences were not significant for Hispanic and black men.

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.

METHODS

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.

Statistical Analysis

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.

RESULTS

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).

DISCUSSION

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.

CONCLUSIONS

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.Author Affiliations: Department of Medicine, Kaiser Permanente Oakland Medical Center (LHL, JCL), Oakland, CA; Division of Research, Kaiser Permanente Northern California (MC, JRG, JCL), Oakland, CA.

Source of Funding: None.

Author Disclosures: Ms Chandra has previously received research funding from Amgen. Dr Lo has previously received research funding from Amgen and Sanofi. The remaining 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 (LHL, MC, JCL); acquisition of data (MC, JCL); analysis and interpretation of data (LHL, MC, JRG, JCL); drafting of the manuscript (LHL, JCL); critical revision of the manuscript for important intellectual content (LHL, MC, JRG, JCL); statistical analysis (MC); provision of patients or study materials (JCL); administrative, technical, or logistic support (LHL, JRG, JCL); and supervision (JCL).

Address Correspondence to: Joan C. Lo, MD, Kaiser Permanente Northern California, 2000 Broadway, Oakland, CA 94612. E-mail: Joan.C.Lo@kp.org. REFERENCES

1. Burge R, Dawson-Hughes B, Solomon DH, Wong JB, King A, Tosteson A. Incidence and economic burden of osteoporosis-related fractures in the United States, 2005-2025. J Bone Miner Res. 2007;22(3):465-475. doi: 10.1359/jbmr.061113.

2. Brauer CA, Coca-Perraillon M, Cutler DM, Rosen AB. Incidence and mortality of hip fractures in the United States. JAMA. 2009;302(14):1573-1579. doi: 10.1001/jama.2009.1462.

3. Orces CH. In-hospital hip fracture mortality trends in older adults: the National Hospital Discharge Survey, 1988-2007. J Am Geriatr Soc. 2013;61(12):2248-2249. doi: 10.1111/jgs.12567.

4. Stevens JA, Rudd RA. The impact of decreasing U.S. hip fracture rates on future hip fracture estimates. Osteoporos Int. 2013;24(10):2725-2728. doi: 10.1007/s00198-013-2375-9.

5. Zingmond DS, Melton LJ 3rd, Silverman SL. Increasing hip fracture incidence in California Hispanics, 1983 to 2000. Osteoporos Int. 2004;15(8):603-610. doi: 10.1007/s00198-004-1592-7.

6. Jacobsen SJ, Goldberg J, Miles TP, Brody JA, Stiers W, Rimm AA. Race and sex differences in mortality following fracture of the hip. Am J Public Health. 1992;82(8):1147-1150.

7. Lo JC, Zheng P, Grimsrud CD, et al. Racial/ethnic differences in hip and diaphyseal femur fractures. Osteoporos Int. 2014;25(9):2313-2318. doi: 10.1007/s00198-014-2750-1.

8. Pothiwala P, Evans EM, Chapman-Novakofski KM. Ethnic variation in risk for osteoporosis among women: a review of biological and behavioral factors. J Womens Health (Larchmt). 2006;15(6):709-719. doi: 10.1089/jwh.2006.15.709.

9. Endo Y, Aharonoff GB, Zuckerman JD, Egol KA, Koval KJ. Gender differences in patients with hip fracture: a greater risk of morbidity and mortality in men. J Orthop Trauma. 2005;19(1):29-35.

10. Penrod JD, Litke A, Hawkes WG, et al. The association of race, gender, and comorbidity with mortality and function after hip fracture. J Gerontol A Biol Sci Med Sci. 2008;63(8):867-872.

11. Kannegaard PN, van der Mark S, Eiken P, Abrahamsen B. Excess mortality in men compared with women following a hip fracture. National analysis of comedications, comorbidity and survival. Age Ageing. 2010;39(2):203-209. doi: 10.1093/ageing/afp221.

12. Haentjens P, Magaziner J, Colón-Emeric CS, et al. Meta-analysis: excess mortality after hip fracture among older women and men. Ann Intern Med. 2010;152(6):380-390. doi: 10.7326/0003-4819-152-6-201003160-00008.

13. Forsén L, Sogaard AJ, Meyer HE, Edna T, Kopjar B. Survival after hip fracture: short- and long-term excess mortality according to age and gender. Osteoporos Int. 1999;10(1):73-78.

14. Sterling RS. Gender and race/ethnicity differences in hip fracture incidence, morbidity, mortality, and function. Clin Orthop Relat Res. 2011;469(7):1913-1918. doi: 10.1007/s11999-010-1736-3.

15. Wehren LE, Hawkes WG, Orwig DL, Hebel JR, Zimmerman SI, Magaziner J. Gender differences in mortality after hip fracture: the role of infection. J Bone Miner Res. 2003;18(12):2231-2237. doi: 10.1359/jbmr.2003.18.12.2231.

16. Alegre-López J, Cordero-Guevara J, Alonso-Valdivielso JL, Fernández-Melón J. Factors associated with mortality and functional disability after hip fracture: an inception cohort study. Osteoporos Int. 2005;16(7):729-736. doi: 10.1007/s00198-004-1740-0.

17. Hawkes WG, Wehren L, Orwig D, Hebel JR, Magaziner J. Gender differences in functioning after hip fracture. J Gerontol A Biol Sci Med Sci. 2006;61(5):495-499.

18. Ekström W, Samuelsson B, Ponzer S, Cederholm T, Thorngren KG, Hedström M. Sex effects on short-term complications after hip fracture: a prospective cohort study. Clin Interv Aging. 2015;10:1259-1266. doi: 10.2147/CIA.S80100.

19. Holt G, Smith R, Duncan K, Hutchison JD, Gregori A. Gender differences in epidemiology and outcome after hip fracture: evidence from the Scottish Hip Fracture Audit. J Bone Joint Surg Br. 2008;90(4):480-483. doi: 10.1302/0301-620X.90B4.20264.

20. Fransen M, Woodward M, Norton R, Robinson E, Butler M, Campbell AJ. Excess mortality or institutionalization after hip fracture: men are at greater risk than women. J Am Geriatr Soc. 2002;50(4):685-690.

21. Ebeling P. Osteoporosis in men: why change needs to happen. International Osteoporosis Foundation website. http://share.iofbonehealth.org/WOD/2014/thematic-report/WOD14-Report.pdf. Published October 2014. Accessed April 1, 2016.

22. Wright NC, Saag KG, Curtis JR, et al. Recent trends in hip fracture rates by race/ethnicity among older US adults. J Bone Miner Res. 2012;27(11):2325-2332. doi: 10.1002/jbmr.1684.

23. Lo JC, Srinivasan S, Chandra M, et al. Trends in mortality following hip fracture in older women. Am J Manag Care. 2015;21(3):e206-e214.

24. Deyo RA, Cherkin DC, Ciol MA. Adapting a clinical comorbidity index for use with ICD-9-CM administrative databases. J Clin Epidemiol. 1992;45(6):613-619.

25. 2010 Census: United States profile. United States Census Bureau website. http://www2.census.gov/geo/maps/dc10_thematic/2010_Profile/2010_Profile_Map_United_States.pdf. Published July 15, 2011. Accessed July 22, 2011.

26. U.S. Preventive Services Task Force. Screening for osteoporosis in postmenopausal women: recommendations and rationale. Ann Intern Med. 2002;137(6):526-528.

27. U.S. Preventive Services Task Force. Screening for osteoporosis: U.S. preventive services task force recommendation statement. Ann Intern Med. 2011;154(5):356-364. doi: 10.7326/0003-4819-154-5-201103010-00307.

28. Cosman F, de Beur SJ, LeBoff MS, et al. Clinician’s guide to prevention and treatment of osteoporosis. Osteoporosis Int. 2014;25(10):2359-2381. doi: 10.1007/s00198-014-2794-2.

29. Qaseem A, Snow V, Shekelle P, Hopkins R Jr, Forciea MA, Owens DK; Clinical Efficacy Assessment Subcommittee of the American College of Physicians. Screening for osteoporosis in men: a clinical practice guideline from the American College of Physicians. Ann Intern Med. 2008;148(9):680-684.

30. Watts NB. Osteoporosis in men. Endocr Pract. 2013;19(5):834-838. doi: 10.4158/EP13114.RA.

31. Curtis JR, McClure LA, Delzell E, et al. Population-based fracture risk assessment and osteoporosis treatment disparities by race and gender. J Gen Intern Med. 2009;24(8):956-962. doi: 10.1007/s11606-009-1031-8.

32. Kiebzak GM, Beinart GA, Perser K, Ambrose CG, Siff SJ, Heggeness MH. Undertreatment of osteoporosis in men with hip fracture. Arch Intern Med. 2002;162(19):2217-2222.

33. Adams AL, Shi J, Takayanagi M, Dell RM, Funahashi TT, Jacobsen SJ. Ten-year hip fracture incidence rate trends in a large California population, 1997-2006. Osteoporos Int. 2013;24(1):373-376. doi: 10.1007/s00198-012-1938-5.

34. Sullivan KJ, Husak LE, Altebarmakian M, Brox WT. Demographic factors in hip fracture incidence and mortality rates in California, 2000-2011. J Orthop Surg Res. 2016;11:4. doi: 10.1186/s13018-015-0332-3.

35. Nam HS, Shin MH, Zmuda JM, et al; Osteoporotic Fractures in Men (MrOS) Research Group. Race/ethnic differences in bone mineral densities in older men. Osteoporos Int. 2010;21(12):2115-2123. doi: 10.1007/s00198-010-1188-3.

36. Nelson DA, Jacobsen G, Barondess DA, Parfitt AM. Ethnic differences in regional bone density, hip axis length, and lifestyle variables among healthy black and white men. J Bone Miner Res. 1995;10(5):782-787. doi: 10.1002/jbmr.5650100515.

37. George A, Tracy JK, Meyer WA, Flores RH, Wilson PD, Hochberg MC. Racial differences in bone mineral density in older men. J Bone Miner Res. 2003;18(12):2238-2244. doi: 10.1359/jbmr.2003.18.12.2238.

38. Shin MH, Zmuda JM, Barrett-Connor E, et al; Osteoporotic Fractures in Men (MrOS) Research Group. Race/ethnic differences in associations between bone mineral density and fracture history in older men. Osteoporos Int. 2014;25(3):837-845. doi: 10.1007/s00198-013-2503-6.

39. Marshall LM, Zmuda JM, Chan BK, et al; Osteoporotic Fractures in Men (MrOS) Research Group. Race and ethnic variation in proximal femur structure and BMD among older men. J Bone Miner Res. 2008;23(1):121-130. doi: 10.1359/jbmr.070908.

40. Travison TG, Beck TJ, Esche GR, Araujo AB, McKinlay JB. Age trends in proximal femur geometry in men: variation by race and ethnicity. Osteoporos Int. 2008;19(3):277-287. doi: 10.1007/s00198-007-0497-7.

41. Zengin A, Pye SR, Cook MJ, et al. Ethnic differences in bone geometry between white, black and South Asian men in the UK. Bone. 2016;91:180-185. doi: 10.1016/j.bone.2016.07.018.

42. Gordon NP. Sociodemographic and health-related characteristics of members aged 65 and over in Kaiser Permanente’s Northern California region, 2011. Kaiser Permanente website. https://divisionofresearch.kaiserpermanente.org/projects/memberhealthsurvey/SiteCollectionDocuments/mhs_seniors_report_%202011_regional.pdf. Published December 2012. Accessed October 7, 2015.

43. Beaupre LA, Morrish DW, Hanley DA, et al. Oral bisphosphonates are associated with reduced mortality after hip fracture. Osteoporos Int. 2011;22(3):983-991. doi: 10.1007/s00198-010-1411-2.

44. Dy CJ, Lane JM, Pan TJ, Parks ML, Lyman S. Racial and socioeconomic disparities in hip fracture care. J Bone Joint Surg Am. 2016;98(10):858-865. doi: 10.2106/JBJS.15.00676.

45. Graham JE, Chang PF, Bergés IM, Granger CV, Ottenbacher KJ. Race/ethnicity and outcomes following inpatient rehabilitation for hip fracture. J Gerontol A Biol Sci Med Sci. 2008;63(8):860-866.

46. Holt-Lunstad J, Smith TB, Layton JB. Social relationships and mortality risk: a meta-analytic review. PLoS Med. 2010;7(7):e1000316. doi: 10.1371/journal.pmed.1000316.

47. Ottenbacher KJ, Smith PM, Illig SB, et al. Disparity in health services and outcomes for persons with hip fracture and lower extremity joint replacement. Med Care. 2003;41(2):232-241. doi: 10.1097/01.MLR.0000044902.01597.54.

48. Nguyen-Oghalai TU, Ottenbacher KJ, Kuo YF, et al. Disparities in utilization of outpatient rehabilitative care following hip fracture hospitalization with respect to race and ethnicity. Arch Phys Med Rehabil. 2009;90(4):560-563. doi: 10.1016/j.apmr.2008.10.021.