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Risk Factors for Osteoporosis in Postmenopausal African-American Women

Posted on: Saturday, 18 December 2004, 03:00 CST

Key words: African-American - Bone mineral density - Osteoporosis - Postmcnopausal - Risk factors

SUMMARY

Background: Although postmenopausal African-American women are at lower risk for osteoporosis-related fractures compared with white women, fractures in African-American women are associated with significantly higher morbidity and mortality. Therefore, early diagnosis and treatment of osteoporosis in this population is just as important as it is for other ethnic groups and worthy of the attention of physicians and healthcare organizations.

Objective: The purpose of this study was to evaluate risk factors for osteoporosis in postmenopausal African-American women.

Design: This was a retrospective, case-control study in 201 postmenopausal African-American women at a community-based osteoporosis center. Spine and hip bone mineral density measurements were obtained by dual-energy x-ray absorptiometry. Patient and family medical history, past and present pharmaceutical use, and dietary and exercise habits were collected using a patient self- administered questionnaire.

Results: Using the manufacturer's African-American referent database, 56 women had osteoporosis, 99 had osteopenia, and 46 had normal bone mineral density. Risk factors more common in the osteoporotic group compared with the normal group included sedentary lifestyle (P < 0.03), family history of osteoporosis (P < 0.03), low body mass index (P < 0.05), and history of bilateral oophorectomy (P < 0.03). Polyarthritis was more prevalent in the normal versus the osteoporotic group (P < 0.001). In addition, premenopausal use of oral contraceptives (P < 0.005) and postmenopausal use of estrogen therapy (P < 0.05) were more common in the normal compared with the osteoporotic group.

Conclusions: Many risk factors for osteoporosis in African- American women are similar to those in white women and can aid in the selection of patients in need of bone density testing.

Introduction

Although postmenopausal African-American women are at lower risk for all categories of osteoporosis-related fractures compared with white women, the incidence of fractures related to osteoporosis and its attendant morbidity and mortality remains substantially high in this population1-4. Using data from women ≥ 65 years of age enrolled in the US Medicare program from 1986 to 1990, Barrett et al. found that the overall incidence of fractures attributed to osteoporosis was 3.1% in African-American and 8% in white women2. Thus, osteoporotic fractures are 2.6 times more common in older white women than in similarly aged African-American women, yet the absolute incidence is significantly high in both populations.

For the African-American patient population, osteoporotic fracture may be a more serious prognostic clinical event than for postmenopausal white women. In a Medicaid population in Georgia studied from 1992 to 1994, African-American postmenopausal women were 3 times more likely to die within 3 years of sustaining any osteoporotic fracture than postmenopausal white women3. Therefore, although osteoporotic fractures may be less prevalent in African- American women than their white peers, the consequences are potentially more serious.

Table 1. Medical history and osteoporosis risk factor questions used for patient self-reports

The collection and analysis of data related to osteoporosis in postmenopausal African-American women is an important step in the characterization of the disease for this patient population. Epidemiological data show that osteoporosis is a serious health issue for African-American women, but in contrast to the white population, there is a paucity of clinical data to guide clinicians in designing strategies to evaluate and treat African-American women with osteoporosis. This retrospective case-control study evaluated risk factors for African-American women with osteoporosis to assist clinicians in selecting appropriate patients for bone mineral density (BMD) testing and treatment.

Methods

Data were collected from patients who received initial dual- energy x-ray absorptiometry (DXA) bone density testing at the Osteoporosis Center of Atlanta between 1992 and 2002. All patients undergoing testing were cither self-referred or referred by their primary care physicians. All patients underwent DXA testing of the nondominant total hip and posteroanterior (PA) lumbar spine using Hologic QDR densitometers (QDR-IOOO, QDR-4500A, or Delphi; Hologic, Bedford, MA, USA]. DXA tests were conducted by manufacturer- certified DXA technologists in the standardized manner recommended in the manufacturer's device manual.

A patient self-administered osteoporosis risk factor questionnaire (Table 1) was used to collect patient medical history, family medical history, past and present drug use, and dietary and exercise habits. Past drug use included all pharmacotherapies received at least once by the patient prior to the initial DXA but stopped before the DXA was obtained; present drug use included pharmacotherapies started before the initial DXA that were being taken at the time of the DXA test. Every question was identified with a unique number and was written such that the answer to each was either 'yes' or 'no.' The structure of the questionnaire allowed each positive response to be entered into The Osteo Report (Centauri Software, Atlanta, GA, USA) data management software program by the corresponding question number.

Using The Osteo Report's proprietary search engine, Oracle, the patient database was queried using the following search terms: 'African American', 'female', and 'postmenopausaF. Of the 6966 patients in The Osteo Report's patient database at the time of the search, the initial query returned 201 patients. Data for these patients were saved to a new database that was queried further to define groups of postmenopausal African-American women with osteoporosis, osteopenia, and normal BMD based on the manufacturer's referent BMD ranges for African-American women. These diagnostic categories were developed according to the World Health Organization (WHO) guidelines for classification using the patient's T-score for the PA L1-L4 spine or the nondominant total hip: normal BMD (T- score > -1), osteopenia (T-score ≤ -1 and > -2.5), and osteoporosis (T-score ≤ -2.5)5. T-scores were calculated using the following formula:

Table 2. Normal bone mineral density cutoffs for calculation of T- scores

Table 3. Demographic characteristics of study population*

T-score = (P - YA)/SD

where P = the patient's BMD in g/cm^sup 2^, YA = the young normal referent BMD in g/cm^sup 2^, and SD = the standard deviation of the young normal referent group.

The densitometer manufacturer (Hologic) provided the African- American referent database used for calculation of T-scores. The manufacturer used published data from the Third National Health and Nutrition Examination Survey (NHANES III) as the referent database for total hip T-scores, and the manufacturer's proprietary African- American referent database was used to calculate T-scores at the spine (Table 2). Patients were classified as normal, osteopenic, or osteoporotic based upon the lower of the 2 T-scores, which is consistent with the International Society for Clinical Densitometry's consensus statement on the use of bone density testing for the diagnosis of osteoporosis6.

A Student's f-test was used to analyze the differences between groups (normal versus osteopenic and osteoporotic, and osteopenic versus osteoporotic) for age and body mass index ([BMI], weight in kilograms divided by height in meters squared). The difference between groups for the prevalence of osteoporosis risk factors was analyzed using the Fisher exact test. Statistical significance was set at 0.05. SAS software (SAS Institute, Inc., Gary, NC, USA) was used for all analyses.

Results

Patient characteristics are presented in Table 3. Of the 201 patients, 56 were osteoporotic, 99 were osteopenic, and 46 had normal BMD using the WHO diagnostic guidelines (Table 4). The mean age was similar among the 3 diagnostic groups. Height was greater in the normal group compared with the osteopenic group (P < 0.05). Weight and BMI were lower in both the osteoporotic and osteopenic groups compared with the normal group (F < 0.05).

Results from the patient self-reported medical history of conditions and factors that affect risk for osteoporosis are displayed in Table 5. Risk factors that were more prevalent in the osteoporotic group compared with the normal group included sedentary lifestyle (P < 0.03), a family history of osteoporosis (P < 0.03), and a history of bilateral oophorectomy (P < 0.03). A medical history of polyarthritis was more common in the normal group versus the osteoporotic group (P < 0.001). Other factors more common in the normal group than in the osteoporotic group included consumption of 2 or more soft drinks daily (P < 0.03) and a history of premature menopause (P < 0.05). The number of patients with self-reported fractures was not statistically different among the 3 groups (data not shown).

Table 4. Average T-scores and BMD values*

Table 5. Patient self-reported history of factors that affect risk for osteoporosis*

Information was also collected on past and present medical treatments for osteoporosis at the time of the patient's initial bone density test (Table 6). There were no significant \differences between the groups with respect to past medical treatments with agents approved by the US Food and Drug Administration for treatment or prevention of osteoporosis. However, previous use of birth control pills was found to be more common in the normal (P < 0.005) versus the osteoporotic group. With regard to present drug treatment for osteoporosis, more women classified as osteoporotic reported using alendronate (P < 0.04) and etidronate (P < 0.04) compared with the normal group. More women in the normal group, when tested, were currently using estrogen therapy compared with the osteoporotic group (P < 0.05). Use of inhaled or oral glucocorticoids was similar between the 2 groups (past use P = 0.33, present use P = 0.18).

Discussion

In this retrospective case-control study of o.steoporosis in postmenopausal African-American women, we used bone densitometry to classify patients into diagnostic groups and a patient self- administered questionnaire to gather risk factor information. Our findings indicate that African-American and white women share some of the same risk factors for osteoporosis. Postmenopausal African- American women with osteoporosis were more likely to have a low BMI, sedentary lifestyle, bilateral oophorectomy, and a family history of osteoporosis than women with normal BMD. These conditions are often cited as risk factors for other ethnic and racial groups and are consistent with risk factors published by the National Osteoporosis Foundation7.

Women with osteopenia and osteoporosis had significantly lower body weight and BMI than women with normal BMD. In addition, more women with normal BMD were overweight than women with osteoporosis; the difference between groups approached statistical significance (P = 0.051). BMI findings, in general, agreed with results found in other studies of older African-American women8,9. In a case-control study in African-American women hospitalized for hip fracture, low body mass was found to be the strongest predictor of hip fracture when patients were compared with community or hospital controls9. Thus, low body weight and BMI are good indicators of low BMD and high fracture risk in African-American women.

Table 6. Past and present history of drug therapy pertinent to osteoporosis

Past use of birth control pills and present use of estrogen were more common in patients with normal bone density. These results are consistent with findings in postmenopausal women of other racial and ethnic groups. Studies in predominantly white women have shown that prior use of oral contraceptives is associated with significantly higher BMD in postmenopausal and perimenopausal women, compared with women who have never used oral contraceptives10-12. In a review of randomized controlled trials for the prevention or treatment of osteoporosis, hormone therapy had a consistent positive effect on BMD in postmenopausal women13. Most of the participants in the reviewed studies were white14-16. Although hormone therapy has been shown to be protective against osteoporosis, results from the Women's Health Initiative indicate that estrogen and estrogen- progestin (hormone therapy) therapy are associated with an increased risk of stroke17,18. The combination hormone therapy is also associated with an increased risk of invasive breast cancer, coronary heart disease, and venous thromboembolic events17. Therefore, patients should be counseled on the risks and benefits of estrogen and hormone therapy before initiating treatment.

A medical history of polyarthritis was less common in patients with osteoporosis than in those with normal BMD. Other studies have found an inverse relationship between bone density and osteoarthritis or spondylosis; however, the reason for this relationship is not fully understood19,20. Recent reports suggest that patients with osteoarthritis have genetic and/or biochemical factors that may contribute to an increase in bone density20.

There were some unexpected findings in this study. A history of early menopause and heavy daily intake of soft drinks were significantly more common in the normal group than the osteoporotic group. These findings should be interpreted with caution, however, because small sample sizes could introduce type 1 and type 2 errors into these comparisons. A larger sample size may have resulted in the identification of additional risk factors or significant differences in other risk factors between the groups. Pertinent to this discussion is the fact that only 201 African-American postmenopausal women were identified over a period of 10 years (< 3% of the population database).

Another unexpected finding was the high prevalence of osteoporosis and osteopenia in this group of postmenopausal African- American women; 28% were osteoporotic and 49% were osteopenic. These percentages are similar to values published for the postmenopausal white population of similar age, and such findings should not be regarded as typical for postmenopausal African-American women21. Because these patients were either referred by their physician or self-selected for bone density testing, these and all observations are potentially influenced by selection bias and cannot be generalized to all African-Americans.

Another potential limitation of this study was that the data were collected through a self-administered questionnaire, and therefore subject to interpretation. Furthermore, the questionnaire has not been validated by scientific method. However, it has been perfected through use as a risk factor assessment tool clinically for 15 years in thousands of patients at the Osteoporosis Center of Atlanta.

Although African-American women have a higher average BMD than their age-matched white counterparts21,22, osteoporosis remains underdiagnosed and undertreated in this population. In a group of elderly African-American women studied in a managed care setting, 48% had low bone mass or osteoporosis and 13% had suffered a fracture within the previous 2 years23. All of these women were eligible for Medicare or Medicaid, but only 30% of those with low bone mass or osteoporosis were receiving treatment with an antiresorptive agent and/or calcium and vitamin D. Such under- recognition can have serious consequences. The mortality rate in African-American women after suffering a fracture is 2 to 3 times higher than in white women1,4. Therefore, despite the lower prevalence of osteoporosis and fracture rates in the African- American population compared with the white population, early identification and treatment of African-American women at risk for osteoporotic fracture is warranted.

Conclusions

These data indicate that African-American and white women share many of the same risk factors for osteoporosis including low BMI, sedentary lifestyle, bilateral oophorectomy, and a family history of osteoporosis. These findings suggest that the identification of risk factors can assist clinicians in the diagnosis and treatment of osteoporosis in postmenopausal African-American women; however, larger studies are needed to develop guidelines for the management of this population.

Although osteoporotic fractures are about 40% less prevalent in postmenopausal African-American women compared with white women, this disease remains a significant cause of morbidity and mortality for this population. Therefore, as with postmenopausal white women, postmenopausal African-American women with salient risk factors for osteoporosis should be tested using central DXA, and if found to have low bone density, should be considered for treatment to prevent osteoporotic fractures.

Acknowledgments

The author wishes to thank E. J. (Bunny) Rogers of the Alliance for Better Bone Health, for her encouragement and support of this article, Yuning Liao of Aventis Pharmaceuticals for providing statistical analysis, and Mary Beth Poole and Kelly Reith for their editorial support.

References

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2. Barrett JA, Baron JA, Karagas MR, Beach ML. Fracture risk in the US Medicare population. J Clin Epidemiol 1999;52:243-9

3. Kotzan JA, Martin BC, Reeves JH, Wade W The impact of race and fractures on mortality in a postmenopausal Medicaid population. Clin Ther 1999;21:1988-2000

4. Kellie SE, Brody JA. Sex-specific and race-specific hip fracture rates. Am J Public Health 1990;80:326-8

5. Kanis JA, Melton 3rd LJ, Christiansen C, Johnston CC, Khaltacv N. The diagnosis of osteoporosis. J Bone Miner Res 1994;9: 1137-41

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7. National Osteoporosis Foundation. Physician's Guide to Prevention and Treatment of Osteoporosis. Washington, DC: National Osteoporosis Foundation, 2003

8. Bohannon AD, Hanlon JT, Landerman R, Gold DT Association of race and other potential risk factors with nonvertebral fractures in community-dwelling elderly women. Am J Epidemiol 1999; 149:1002-9

9. Grisso JA, Kelsey JL, Strom BL, et al. Risk factors for hip fracture in black women. The Northeast Hip Fracture Study Group. N Engl J Med 1994;330:1555-9

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13. Nelson H, Helfand M. Hormone replacement therapy and osteoporosis. Systematic evidence review Number 12. Rockville, MD. Available at: http://\www.ahrci.gov/clinic/serfiles.htm. Accessed June 03, 2003

14. Writing Group for the PEPI Trial. Effects of hormone therapy on bone mineral density: results from the postmenopausal estrogen/ progestin interventions (PEPI) trial. The Writing Group for the PEPI. JAMA 1996;276:1389-96

15. Ravn P, Bidstrup M, Wasnich RD, et al. Alendronate and estrogen-progestin in the long-term prevention of bone loss: four- year results from the early postmenopausal intervention cohort study. A randomized, controlled trial. Ann Intern Med 1999;131:935- 42

16. Recker RR, Davies KM, Dowd RM, Heaney RP. The effect of low- dose continuous estrogen and progesterone therapy with calcium and vitamin D on bone in elderly women. A randomized, controlled trial. Ann Intern Med 1999; 130:897-904

17. Rossouw J, Anderson G, Prentice R, et al. Risks and benefits of estrogen plus progestin in healthy postmenopausal women: principal results from the Women's Health Initiative randomized controlled trial. JAMA 2002;288:321-33

18. Anderson GL, Limacher M, Assaf AR, et al. Effects of conjugated equine estrogen in postmenopausal women with hysterectomy: the Women's Health Initiative randomized controlled trial. JAMA2004;291:1701-12

19. Amin S. Osteoarthritis and bone mineral density: what is the relation and why does it matter? J Rheumatol 2002;29:1348-9

20. Miyakoshi N, Itoi E, Murai H, Wakabayashi I, Ito H, Minato T. Inverse relation between osteoporosis and spondylosis in postmenopausal women as evaluated by bone mineral density and semiquantitativc scoring of spinal degeneration. Spine 2003;28:492- 5

21. Looker AC, Orwoll ES, Johnston Jr. CC, et al. Prevalence of low femoral bone density in older US adults from NHANES III. J Bone Miner Res 1997;12:1761-8

22. Siris ES, Miller PD, Barrett-Connor E, et al. Identification and fracture outcomes of undiagnosed low bone mineral density in postmenopausal women: results from the National Osteoporosis Risk Assessment. JAMA 2001 ;286: 2815-22

23. Orwig DL, Brandt N, Zimmerman G, Smith A. Bonestrengthening medication use and low bone density in black elderly women. J Bone Min Res 2002; 17:5259

CrossRef links are available in the online published version of this paper: http://www.cmrojournal.com

Paper CMRO-2681_4, Accepted for publication: 26 July 2004

Published Online: 16 September 2004

doi: 10.1185/030079904X3285

Grattan C. Woodson

The Osteoporosis Center of Atlanta, Decatur, GA 30033, USA

Address for correspondence: Dr Grattan Woodson, The Osteoporosis Center of Atlanta, 2801 N. Decatur Road, Suite 375, Decatur, GA 30033, USA. Tel.: +1-404-298-9951; Fax: +1-404-298-5577; email: gwoodson@mindspring.com

Copyright Librapharm Oct 2004

Source: Current Medical Research and Opinion

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