University of California, San Diego, La Jolla, CA, USA.
Correspondence: Elizabeth Barrett-Connor, M.D., Assistant Professor and Chief, Division of Epidemiology, Department of Family and Preventive Medicine, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 920930607, USA. E-mail: ebarrettconnor{at}ucsd.edu
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Abstract |
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Methods In all three groups, BMD was measured by DXA (Hologic 2000) at the hip, lumbar spine, and total body. Lifestyle variables and anthropometric measures were assessed by standard methodology; medication and supplement use were validated by a nurse.
Results Regardless of the variables used to represent body size in the regression modelling, either body mass index or lean and fat tissue mass, ethnic differences were minimal across the three groups. The only significant differences observed using the two fully adjusted models (age, height, body mass index or lean and fat tissue mass, smoking, alcohol, exercise, current oestrogen and calcium supplement use, and osteoarthritis) were at the total body BMD site where Filipinas had significantly higher BMD than the Caucasians or Hispanics, whose total body BMD was similar to one another. The independent variables in the fully adjusted models explained approximately 2040% of the variation in BMD at each of the four sites. Income or occupation did not help explain BMD differences, but a pattern of increased BMD among those with some college education in all three groups was observed.
Conclusions Accounting for body size using either body mass index or fat and lean tissue mass along with height and other lifestyle variables minimizes ethnic differences and explains a considerable amount of variation in mean BMD among older ethnic minority and Caucasian women.
Accepted 3 October 2002
Osteoporosis and related fracture are major known causes of morbidity and mortality in ageing Caucasians. Low bone mineral density (BMD), one of the major risk factors associated with osteoporosis, has been characterized extensively among Caucasians of northern European ancestry, and risk factors for low bone density have been described in many epidemiological studies.
Ethnic minorities constitute an increasingly large proportion of the total US population, as the number of ethnic minority people over the age of 65 is expected to double during the next half century.1 Ethnicity and its associated cultural values, behaviours, dietary practices, and lifestyle choices impact the health status of any given population, and bone mass is no exception. Nevertheless, few studies have examined bone mass in Hispanic, particularly Mexican American postmenopausal women,24 and no studies of bone mass have been reported in Filipinas.
The twofold purpose of the present study was to determine: (1) if levels of BMD at the hip, spine, and total body varied significantly among postmenopausal women of northern European (Caucasian), Philippine, or Hispanic ancestry and whether any differences could be attributed to variations in body size and other common risk factors for osteoporosis; and, (2) if using different measures of body size as independent variables, e.g. body mass index versus lean and fat tissue mass, affected these results.
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Methods |
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Caucasians
Between 1972 and 1974, 82% of all adult residents of the southern California community of Rancho Bernardo (n = 6339) were surveyed to estimate the prevalence of heart disease risk factors.5,6 From May 1992 to January 1997, all surviving, non-institutionalized members of the Rancho Bernardo cohort (n = 2569) were asked to participate in a study of osteoporosis (Visit 7). A total of 1781 individuals attended this clinic visit (participation rate = 69.3%), of whom 1082 were women aged 3097 years.
Filipinas
Beginning in October 1995, Filipinas aged 40 years residing in northern San Diego County were recruited to participate in a study of osteoporosis using the identical protocol employed by the Rancho Bernardo Study. Most participants were residents of Mira Mesa, a middle-class community with a large Filipino population located in north San Diego County. This population was chosen because it is located 10 miles from the research clinic in Rancho Bernardo where the Caucasian cohort resides. Additionally, Filipinos are not identified separately in the San Diego census, so random sampling of the entire county was not feasible. Participants were recruited through traditional convenience sampling methods: contact with Filipino community leaders, articles and advertisements in Filipino newspapers, participant referrals, presentations at meetings of community groups such as predominantly Filipino church congregations, and the Filipino Nurses Association. Recruitment brochures and informed consent documents were translated into Tagalog, the primary language of the Philippines.
A total of 746 Filipinas were contacted as of December 1998, of whom 452 (61%), aged 3986 years, participated in this study. Filipinas who were contacted but did not participate were either too young, would not give their age, did not reside locally, cancelled their appointments, or refused. Participants were examined in the Rancho Bernardo/University of California, San Diego (UCSD) Research Clinic, the same facility used for the Caucasian participants. Questionnaires were administered in English by a Philippine-born female nurse who translated into Tagalog when necessary. All participants spoke functional English.
Hispanics
Beginning in August 1995, and ending in July 1996, 251 Hispanic women, aged 4484 years, were contacted and asked to volunteer for a study of osteoporosis, again using protocol identical to the Rancho Bernardo Study. Recruitment strategy was similar to that for the Filipinas. Participants were volunteers recruited from the Hispanic community through flyers, church groups, participant referrals, community newsletters, and outpatient clinics that serve the Hispanic community in San Diego County. A total of 212 women who were contacted initially agreed to participate (85%). Those identified as eligible by telephone screening who did not participate (n = 39) either lacked transportation to the clinic, were experiencing personal or family illness, or did not keep their scheduled appointments. Study participants were seen in the Clinical Research Facility located on the UCSD campus.
Questionnaires and informed consent documents were translated into Spanish and administered by a Mexican-born, native Spanish speaking, female interviewer. Participants were allowed to choose either the Spanish or English version of the self-administered portion of the questionnaires.
Sample sizes
The Caucasian women were on average older than the Filipinas and Hispanics, therefore, in order to increase comparability and exclude women who were pre- or perimenopausal, the sample sizes for these analyses were limited to women aged 50-69 years. After excluding 26 Caucasians and six Filipinas who indicated they were still having periods, and six Filipinas who had missing data for menopausal status, all women included in these analyses were postmenopausal, resulting in a final sample of 354 Caucasians, 285 Filipinas, and 164 Hispanics.
Questionnaires
Data for each group were collected using an identical protocol. Lifestyle habits such as exercise, current smoking, and alcohol use, and demographic characteristics such as age, education, occupation, income, birthplace, marital and employment status, years in US, and ethnic identity were assessed using a questionnaire. A standardized medical interview ascertained menopausal status and osteoarthritis. Use of prescription and non-prescription medications and nutritional supplements were recorded by a nurse who examined pills, prescriptions, vitamins, and minerals brought to the clinic visit for that purpose.
Body size
Height (cm) was determined by a stadiometer to the nearest 0.1 cm, and weight was assessed using a regularly calibrated scale to the nearest 0.1 kg in women wearing light clothing and no shoes. Body mass index was calculated as weight (kg) divided by height (meters2).
Bone mineral density
Bone mineral density was defined as total bone mineral content (gm) divided by the area (cm2). Femoral neck, total hip, lumbar spine, and total body BMD were measured in all three groups using dual-energy X-ray absorptiometry (DXA) (Hologic QDR-2000, Waltham, MA, scanning program Version 5.54). Femoral neck BMD was measured at the narrowest point of the femoral neck and perpendicular to the femoral midline. Total hip BMD was the mean of the femoral neck, greater trochanter, and intertrochanteric regions. Spine BMD was measured in the anteroposterior view and was the mean of lumbar vertebra 14. Total body scans measured bone mineral content and area at 10 regions, and body fat was estimated from data using the total body DXA. It has been shown that the bone density of the head changes with age and body mass index, and when head BMD is excluded from the total body measurement, it is a more accurate predictor of fracture risk.7 Therefore, BMD of the head was subtracted from the total body BMD measurement, but referred to as total body. Axial scans were standardized daily against a phantom, with a precision error of 1%. Precision errors for lean mass, fat mass, and total per cent body fat were approximately 1.2% or less. Bone scans were administered by certified bone density technologists.
Statistical analyses
All analyses were conducted using SAS version 6.12.8 Three separate ethnic group datasets were created, checked for errors and compatibility of coding for all variables, and then concatenated into one dataset for all analyses. Chi-square tests were used to estimate differences in unadjusted proportions and Mantel-Haenszel 2 tests were used to estimate between group differences in adjusted proportions with a two-tailed test of significance (
0.05). Differences between groups in adjusted mean values were estimated using a generalized linear regression model that included a sub-routine for linear trend analysis. Both P-values and 95% CI were calculated. All BMD values for each ethnic group were normally distributed making transformations unnecessary to satisfy the assumptions underlying regression modelling.
In previous studies of women from the Rancho Bernardo cohort, multivariate models estimating BMD used a standard group of covariates shown to affect bone mass, including age, body mass index, current use of oestrogen, thyroid hormone, thiazides, corticosteroids and calcium supplement use, and smoking, exercise, alcohol, and osteoarthritis.915 In the present study, a series of multiple regression models was calculated separately for each ethnic group to determine the set of predictors to be used in all multivariate models with BMD as the dependent variable. The results of these analyses consistently showed that age, body mass index, height, lean and fat tissue mass, current oestrogen use, alcohol consumption, and osteoarthritis were significant predictors of bone mass at all measurement sites within each ethnic group. Smoking, exercise, and calcium supplement use were not significant predictors of bone mass in this study, but were included as independent variables in all multivariate models to be comparable to previous studies. Use of thiazides, corticosteroids, and thyroid hormones were not included in the final group of covariates because they did not alter the results and use was uncommon among the ethnic minority women.
In an attempt to determine which set of variables explained the most variation in BMD for all three ethnic groups, and to examine whether lean and fat tissue mass produced different results compared with using the standard body mass index to represent body size, four regression models were conducted. In addition, Michels and colleagues16 have argued that using body mass index alone to account for body size in a multiple regression analysis is not adequate and recommend the addition of height to the model to account for the joint relation of body size and body composition. Therefore, height was included as an independent variable in all of the regression modelling along with a measure of body size, either body mass index or lean and fat tissue mass.
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Results |
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Overall, the Caucasian women had the highest socioeconomic status (SES), and Hispanics the lowest. About two-thirds of the Caucasians (65%) and the Filipinas (62%) had at least some college education, but only 9% of the Hispanics reported at least one year of college education, and 71% had less than a high school education. Income was never directly assessed in the Rancho Bernardo cohort, but based on the Hollingshead Index, which includes education level of participant and occupation of head of household, most Rancho Bernardo Study participants can be classified as middle- to upper middle-class.17 Only 64% of the Filipina women responded to the income question; of these, 65% reported a household income of <$40 000 per year, and 35% reported an income <$20 000 per year. Seventy-five per cent of the Hispanics indicated their yearly household income was <$20 000.
The majority of the Caucasian households (72%) reported occupations (head of household) in the two highest levels (higher professionals/executives and business managers/lesser professionals), compared with 22% of the Filipinas and 14% of the Hispanics. Conversely, there were higher proportions of Filipino and Hispanic households employed in the next three lower categories, specifically administrative, clerical/sales, and skilled-manual labourers (Caucasians = 27%, Filipinas = 44%, Hispanics = 14%). Only one per cent of the Caucasian households reported employment that was semi- or un-skilled compared with 34% of the Filipinas and 50% of the Hispanics.
Covariates of bone mineral density
All women were postmenopausal, and Hispanics reported a significantly younger age at menopause (45.4 years) compared with the Filipinas (47.3 years), but did not differ significantly from the Caucasian women. Several body size indicators, including mean body mass index, percentage body fat, and lean and fat tissue mass, were significantly higher among the Hispanics compared with the Caucasian and Filipina women (Table 1). Filipinas weighed significantly less, were shorter, and had significantly lower total lean and fat tissue mass compared with the Caucasians and the Hispanics.
Among lifestyle behaviours known to affect BMD, Caucasians were three times more likely than Filipinas and twice as likely as Hispanics to have ever smoked (P < 0.001), with similar differences observed in current smoking rates. Caucasians consumed alcohol significantly more often than those in either ethnic minority group; 41% of Caucasian women drank 3+ times per week versus 1% of Filipina women and 6% of Hispanics (P < 0.001). Approximately two-thirds of the women in each ethnic group reported exercising 3+ times per week; 67% of Caucasians, 66% of Hispanic women, and 64% of the Filipinas (Table 1).
Caucasians were about 2.5 times more likely than Filipinas and about 1.5 times more likely than Hispanics to have ever used oestrogen (P < 0.001). Current oestrogen use was reported by 19% of Filipinas, 38% of Hispanics, and 60% of Caucasian women (P < 0.001). Calcium supplements were used by 28% of the Filipinas, 39% of the Hispanic women, and 46% of the Caucasians (P < 0.05). Rates of self-reported osteoarthritis were similar for Caucasian (18%) and Hispanic women (13%), with a somewhat lower rate in Filipinas (11%, P < 0.05).
Bone mineral density
Bone mineral density levels decreased with increasing age in the ethnic minority women, as reported in Rancho Bernardo Caucasian women.18 When stratified by 5-year age groups, BMD decreased with age category among the ethnic minority women at all four sites in a model controlled for age (within each category), body mass index, current oestrogen use, smoking, exercise, alcohol, calcium supplement use, and self-reported osteoarthritis (data not shown). Linear trends in the same model were significant at all four sites for the Filipinas, and at the femoral neck, total hip, and total body for the Hispanics. Body size increased significantly with increasing tertiles of BMD at all sites in both ethnic minority groups (data not shown).
Multivariate regression Model 1 was adjusted for age, height, and body mass index (Table 2). Filipinas had significantly lower bone density at the lumbar spine (4.7%) compared with Caucasian women, and significantly lower BMD levels at the total hip compared with Hispanics (4.7%). In the same model, Hispanics had significantly lower BMD levels at the total body (1.7%) compared with Caucasians. Model 2 was adjusted for age and height, but lean and fat tissue mass were substituted for body mass index. The results were similar to Model 1 for Filipinas compared with Caucasians: BMD was significantly lower at the lumbar spine (9.2%), and now significantly lower at the total hip (4.2%). For Hispanics, Model 2 was also similar to Model 1: total body BMD and lumbar spine were both significantly lower compared with Caucasians (2% and 4%, respectively). The overall amount of variation in BMD explained by Models 1 and 2 (adjusted r2) were similar at all bone measurement sites and ranged from 15% to 35%.
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Since ethnic minority differences may be related to SES, the three components of SES, income, occupation, and education, were examined in relation to bone mass. Stratification of the ethnic minority groups by income levels (income in the Caucasian women was not collected) did not show significant differences in bone mass at any site (P-values > 0.10, data not shown). Stratification of all three groups by occupation categories revealed a few sporadic differences in BMD levels but after accounting for multiple comparisons, these differences disappeared (data not shown). Stratification of all three groups into those with at least some college versus no college education showed consistently higher BMD among the college educated for all three groups at all four sites. However, none of these differences was statistically significant except for the Hispanics at the total hip (data not shown).
Discussion
The present study is one of the first to examine bone density in two understudied groups of ethnic minority women, Filipinas and Hispanics. Bone mineral density levels at the femoral neck, total hip, lumbar spine, and total body decreased significantly with age and increased significantly with increasing body mass index for all Filipinas (not previously reported) and Hispanics, as has been well-established in other studies of Caucasian postmenopausal women.
Two regression models, both adjusted for age, height, and body size, one using body mass index, and one using lean and fat tissue mass, showed similar results. Bone mineral density was lowest for the Filipina women at the femoral neck and total hip, and significantly lowest at the lumbar spine. Caucasians and Hispanics had similar BMD at the femoral neck and total hip. Hispanics had lower lumbar spine BMD compared with Caucasians and these results were significant using the model that included lean and fat tissue mass. Total body bone mass was lowest in Hispanics for both of the models compared with Caucasians. Despite using different measures of body size, these two models generally yielded similar results at all four sites and a similar proportion of variance in bone mass was explained.
When additional confounding variables (current oestrogen use, current smoking, exercise 3+ times/week, alcohol use 3+ times/week, calcium supplement use, and osteoarthritis) were added to the two models previously mentioned, results were, again, similar for each model. However, after adding these confounders, total body bone density was significantly higher among the Filipinas compared with the other two groups. In general, BMD was similar across all three groups when adjusted for all confounders, regardless of which variables were used to represent body size, except at the total body.
Although Filipinos are the second largest Asian population in the US, and the largest Asian-Pacific Islander group in California,19 health data remain scarce, especially in postmenopausal women. If Filipinos are included in research reports, they are generally grouped together with other diverse ethnic groups under the catch-all title of Asian. The present study appears to be the first large study of bone mass among postmenopausal Filipinas, and therefore these results can only be compared indirectly with BMD studies among other Asians, including Chinese, Japanese, Hawaiian, and Korean women.
In a multicentre study of Japanese, Korean, and Chinese postmenopausal women, Ross and colleagues20 reported lower BMD at most skeletal sites when compared with Caucasians, but these differences were eliminated at all sites except the spine when height, and lean and fat tissue mass were added to the model, similar to the present study. Russel-Aulet et al.21 in a study of premenopausal mixed Asians (mainly Chinese) matched with Caucasian women, concluded that any differences in total body BMD could be explained by body size and oestrogen use, not other known ethnic factors. Other studies have reported significantly lower bone density at the femoral neck, total hip, and lumbar spine among Asian postmenopausal women when compared with Caucasians,2225 but none controlled for lean and fat tissue mass.
Studies of Hispanics,2,3 including results from the National Health and Examination Survey (NHANES) III data,4 have also found BMD levels similar to Caucasians at the hip and total body, comparable to the present study. Conversely, a more recent study of Mexican American women in California26 found these women to have higher hip and total body BMD when compared with non-Hispanic white women. However, the Mexican American sample was relatively small (n = 54), head BMD was not excluded from the total body measurement, and the results were only adjusted for height and body size, not other lifestyle factors known to affect BMD as in the present study.
Brismar and Ringertz7 reported total body BMD was a better predictor of fracture risk when head BMD (20% of the total body measurement) was excluded from the calculation of total body BMD. This anomaly is explained by the fact that total body BMD scans predominantly reflect appendicular cortical bone measurement (all four extremities plus the head), and approximately 80% of total skeletal mass is cortical. Conversely, hip and spine BMD predominantly measure the axial skeleton which includes a higher proportion of trabecular bone. In the present study, the two ethnic minority groups had a higher total body BMD than Caucasians when head BMD was either included or excluded in the measurement (data not shown).
Socioeconomic status is known to affect lifestyle choices such as exercise, smoking, and alcohol consumption, which could in turn influence levels of bone mass. In the present study, no patterns or associations of BMD levels with income or occupation were observed within each ethnic group. However, a pattern of lower BMD at all sites was observed among those without a college education in all three groups. This suggests that education may be a proxy for unmeasured factors associated with better bone density.
This study is one of the largest studies of bone mass among postmenopausal Filipinas to date, yet it has several potential limitations. Although the study is cross-sectional and cannot clearly establish the temporal sequence of events, the participants were relatively young and it is unlikely that differential selection and volunteering could explain these results. Bone loss occurs over long periods of time with the most rapid rate of bone loss in Caucasian women occurring in the 10 years following menopause. It is not known if rates of bone loss with age and menopausal status are the same for Filipinas and Hispanics.
Second, these data clearly are specific to the ethnic minority women in the study. Because the ethnic minority women were recruited through convenience sampling methods, typical of ethnic research studies, rather than a community-based study, as were the Caucasian women (Rancho Bernardo Study), the minority volunteers may have unknown self-selection biases related to migration, cohort effects, health, and SES. Income and education levels were incompletely adjusted across all socioeconomic levels, and no pertinent information on the health and social status of the ethnic minority women before their migration to the US was available.
Third, the questionnaires taken from the Rancho Bernardo protocol and utilized for the Hispanic women were translated into Spanish appropriate for southern California by a bilingual native Spanish translator experienced in medical research, but were not back translated prior to administration. The questionnaires for the Filipina women were not translated into Tagalog (the major dialect spoken by most Filipinos), but were administered in English by a native Filipina Tagalog-speaking bilingual nurse and translated rarely and only when necessary as all participants spoke functional English. Language bias and error although most likely minimal, cannot be excluded.
The findings in this study present new data in Filipinas, a large and very fast growing ethnic minority group in California. Further, these data confirm that accounting for body size is very important, but when a comprehensive group of well-known confounders are considered, ethnic differences are minimized regardless of the variables used in the regression models to represent body size as the standard of evaluation for risk of osteoporosis and subsequent fracture. Additionally, SES did not explain any variation in BMD. The possible clinical significance of the observed lack of ethnic BMD differences is uncertain. Although the models used to explain BMD in these three groups explained 2040% of the variation, the ethnic differences in mean BMD not accounted for by the factors included in this study may be due either to residual or unknown behavioural and environmental confounders specific to Filipinas and Hispanics, or to genetic or constitutional factors. It is clear that future bone studies of ethnic minority groups should begin to focus on within-group variation to identify culturally specific and appropriate possible preventive mechanisms rather than continuing the traditional emphasis on between-group variation and comparison with Caucasian populations.
KEY MESSAGES
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References |
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2 Bauer RL, Haffner SM. Axial skeletal bone density in Mexican American and non-Hispanic white women. J Bone Miner Res 1992; 7(Suppl.):S195, Abstract.
3 Villa ML, Marcus R, Delay RR, Kelsey JL. Factors contributing to skeletal health of postmenopausal Mexican-American women. J Bone Miner Res 1995;10:123342.[ISI][Medline]
4 Looker AC, Orwoll ES, Johnston CC et al. Prevalence of low femoral bone density in older US adults from NHANES III. J Bone Miner Res 1997;12:176168.[ISI][Medline]
5 Barrett-Connor E. The prevalence of diabetes mellitus in an adult community as determined by history or fasting hyperglycemia. Am J Epidemiol 1980;111:70512.[Abstract]
6 Criqui MH, Barrett-Connor E, Austin M. Differences between respondents and non-respondents in a population-based cardiovascular disease study. Am J Epidemiol 1978;108:36772.[Abstract]
7 Brismar TB, Ringertz J. Effect of bone density of the head on total body DEXA measurements in 100 healthy Swedish women. Acta Radiol 1996;37:10106.[ISI][Medline]
8 SAS Institute, Inc. SAS/STAT Users Guide, 1988; Release 6.03. Cary, NC: SAS Institute Inc.
9 Morton DJ, Barrett-Connor E, Edelstein SL. Thiazides and bone mineral density in elderly men and women. Am J Epidemiol 1994; 139:110715.[Abstract]
10 Schneider DL, Barrett-Connor E, Morton DJ. Thyroid hormone use and bone mineral density in elderly women: Effects of estrogen. JAMA 1994;271:124549.[Abstract]
11 Marystone J, Barrett-Connor E, Morton DJ. Inhaled and oral corticosteroids: Their effects on bone mineral density in older adults. Am J Public Health 1995;85:169395.[Abstract]
12 Kim SH, Morton DJ, Barrett-Connor E. Carbonated beverage consumption and bone mineral density among older women: The Rancho Bernardo Study. Am J Public Health 1997;87:27679.[Abstract]
13 Schneider DL, Barrett-Connor E, Morton DJ. Timing of postmenopausal estrogen for optimal bone mineral density: The Rancho Bernardo Study. JAMA 1997;277:54347.[Abstract]
14 Lunde AV, Barrett-Connor E, Morton DJ. Serum albumin and bone mineral density in healthy older men and women: The Rancho Bernardo Study. Osteoporos Int 1998;8:54751.[CrossRef][ISI][Medline]
15 Morton DJ, Barrett-Connor E, Schneider DL. Nonsteroidal anti-inflammatory drugs and bone mineral density in older women: The Rancho Bernardo Study. J Bone Miner Res 1998;13:192431.[ISI][Medline]
16 Michels KB, Greenland S, Rosner BA. Does body mass index adequately capture the relation of body composition and body size to health outcomes? Am J Epidemiol 1998;147:16772.[Abstract]
17 Hollingshead AB. Two Factor Index of Social Position. Privately published, 1957.
18 Blunt BA, Klauber MR, Barrett-Connor E, Edelstein SL. Sex differences in bone mineral density in 1653 men and women in the sixth through tenth decades of life: The Rancho Bernardo Study. J Bone Miner Res 1994;9:133338.[ISI][Medline]
19 Barker JC. Cultural diversitychanging the context of medical practice. West J Med 1992;157:24854.[ISI][Medline]
20 Ross PD, He Y, Yates AJ et al. Body size accounts for most differences in bone density between Asian and Caucasian women. Calcif Tissue Int 1996;59:33943.[CrossRef][ISI][Medline]
21 Russell-Aulet M, Wang J, Thornton JC, Colt E, Pierson RN. Bone mineral density and mass in a cross-sectional study of White and Asian women. J Bone Miner Res 1993;8:57582.[ISI][Medline]
22 Hagiwara S, Miki T, Nishizawa Y, Ochi H, Onoyama Y, Morii H. Quantification of bone mineral content using dual-photon absorptiometry in a normal Japanese population. J Bone Miner Res 1989;4: 21722.[ISI][Medline]
23 Nomura A, Wasnich RD, Heilbrun LK, Ross PD, Davis JW. Comparison of bone mineral content between Japan-born and US-born Japanese subjects in Hawaii. Bone Miner 1989;6:21323.[CrossRef][ISI][Medline]
24 Ross PD, Orimo H, Wasnich RD et al. Methodological issues in comparing genetic and environmental influences on bone mass. Bone Miner 1989;7:6777.[CrossRef][ISI][Medline]
25 Tsai KS, Huang KM, Chieng PU, Su CT. Bone mineral density of normal Chinese women in Taiwan. Calcif Tissue Int 1991;48:16166.[ISI]
26 Taaffe DR, Villa ML, Holloway L, Marcus R. Bone mineral density in older non-Hispanic Caucasian and Mexican-American women: relationship to lean and fat mass. Ann Hum Biol 2000;27:33144.[CrossRef][ISI][Medline]