Bone densitometry of proximal femur in Chinese subjects: gender differences in bone mass and bone areas

Sex- and age-related differences in femoral neck cross-sectional structural changes in mainland Chinese men and women measured using dual-energy X-ray absorptiometry

We investigated age-related changes in estimated bone strength and cross-sectional structure of the femoral neck (FN) in mainland Chinese men and women (according to age and sex) using dual-energy X-ray absorptiometry (DXA). A total of 3855 healthy adults (2713 women, 1142 men; ages 25-91years) were analyzed by FN bone mineral density (BMD) assessment and hip structural/strength analysis (HSA), including cross-sectional moment of inertia (CSMI), cross-sectional area (CSA), section modulus (Z), periosteal diameter (PD), endocortical diameter (ED), and cortical thickness (CT) using DXA. HSA differences between age and sex groups were adjusted for body weight, height and FN BMD. Trends according to age were estimated by linear regression analysis. There was no inverse correlation between HSA parameters and age in young adults. Some HSA parameters (CSMI, CSA, Z, CT) decreased significantly with age, whereas PD and ED increased significantly. Older adults had less estimated bone strength and CT and higher PD and ED (p<0.05) than young adults. Men had greater increases in PD and ED than women across all ages. FN strength decreases with age in both sexes, caused by FN cross-sectional structural deterioration. Indirect comparison of our data with those from other populations showed less age-related FN periosteal apposition in Chinese than Caucasian men, but similar amounts in women. This may partly explain different male/female hip fracture rates among ethnic groups. Chinese men have more structural disadvantages regarding FN geometry during aging than Caucasian men, possibly conferring added susceptibility to hip fracture.

Ethnic differences in composite indices of femoral neck strength

Bone mineral density does not explain race/ethnicity differences in hip fracture risk. In this study, we demonstrated that race/ethnicity differences in composite hip strength indices were consistent with documented race/ethnicity differences in hip fracture risk, suggesting that unlike bone density, the composite indices may represent ethnicity-independent measures of bone strength.

INTRODUCTION

African-American and Asian women have lower risks of hip fracture than Caucasian women, but such racial/ethnic variation in hip fracture risk cannot be explained by bone mineral density (BMD). The composite indices of femoral neck strength integrate femoral neck and body size with BMD and predict hip fracture risk in Caucasian women. We hypothesize that unlike race/ethnic differences in BMD, race/ethnic differences in the composite strength indices would be consistent with race/ethnic differences in hip fracture risk.

METHODS

We studied a community-based sample of Caucasian (n = 968), African-American (n = 512), Chinese (n = 221), and Japanese (n = 239) women, premenopausal or in early perimenopause, from the Study of Women's Health Across the Nation.

RESULTS

Unadjusted indices were similar in Caucasian and African-American women but higher in Asian women. After adjusting for age, body mass index, and menopause status, all three minority groups had higher composite strength indices than Caucasian women. Foreign-born Japanese women had higher unadjusted and adjusted composite strength indices than US-born Japanese women, but such differences by nativity were not observed in Chinese women.

CONCLUSION

We concluded that composite strength indices have the potential to explain racial/ethnic differences in hip fracture risk, suggesting that composite strength indices may represent ethnicity-independent measures of bone strength. This contention needs to be verified by further research on the fracture predictive ability of composite strength indices in multi-ethnic longitudinal cohorts.

Epidemiology and structural basis of racial differences in fragility fractures in Chinese and Caucasians

Chinese have similar vertebral fracture prevalence but lower incidence of hip and distal forearm fractures than in Caucasians. The underlying structural and biomechanical basis of racial differences in bone fragility is still largely undefined but Chinese assemble their smaller appendicular skeleton with thicker cortices and trabeculae compared with Caucasians. Vertebral fracture prevalence is similar by race, but the incidence of hip and distal forearm fractures is lower in Chinese than in Caucasians. This racial dimorphism cannot be explained by differences in areal bone mineral density (aBMD) as aBMD is lower in Chinese mainly due to their smaller size. The underlying structural and biomechanical basis of racial differences in bone fragility is still largely undefined but Chinese assemble their smaller appendicular skeleton with more mineralised bone matrix within it; the cortices are thicker and perhaps less porous while trabeculae are fewer but thicker and more connected. This configuration produces a bone with a lower surface/volume ratio, which in turn reduces the surface available for remodelling to occur upon so that the lower surface/volume ratio may make the bone less exposed to remodelling and the thicker cortices and trabeculae less vulnerable to remodelling when it does occur during advancing age. However, prospective studies are needed to define racial differences at the age of onset, rate of bone loss from the intracortical, endocortical and trabecular components of the endosteal envelope and bone formation upon the periosteal envelope; notions of bone 'loss' are derived mainly from cross-sectional studies. Studies of the site- and surface-specific changes in bone modelling and remodelling are needed to better define racial differences in bone fragility in old age.

Bone mineral density discordance and exploration of one of its causes

Discordances between hip and spine areal density T-score values are common and incompletely understood. In a cohort of 1157 postmenopausal women, discordances of greater than 10% occurred in 91%, with spine bone mineral density (BMD) T-scores significantly less negative than femoral neck (FN) T-scores (p<0.001). However, when T-scores based on bone mineral content (BMC) rather than BMD were used, the mean discordance was not significantly different from 0. This was largely because BMC at the FN had seemingly declined with age less rapidly than had BMD at that site. This can be explained by age-related areal expansion at the hip, which would be missed in the reported BMD output. One consequence is that if BMC-based T-scores are used to classify patients, substantially fewer individuals would have been judged osteoporotic in this cohort (two-thirds fewer for spine and three-fourths fewer for hip).

Femoral neck bone mineral density in ambulatory men with poliomyelitis

We evaluated bilateral femoral neck bone mineral densities (FNBMDs) in 32 men with poliomyelitis and their matched controls. Men with poliomyelitis had significantly lower FNBMD in both legs, and FNBMD was lowest in their shorter legs. Knee extensor strength and regular exercise were important predictive factors associated with decreased FNBMD.

INTRODUCTION

People with poliomyelitis (polio) are prone to leg fractures after mild trauma. The flaccid paralysis, asymmetric involvement, and underdeveloped growth of afflicted legs may lead to osteoporosis of either leg, characterized by different patterns. This study aimed to measure their femoral FNBMD and to explore the factors associated with changes in FNBMD in either leg.

METHODS

We did a prospective study to evaluate bilateral FNBMD with dual-energy X-ray absorptiometry in 32 men with polio (age range, 41-57 years; mean, 47 years) and 32 age- and body mass index-matched controls. Measuring the difference in leg length, we classified the legs of each polio subject as "longer" or "shorter." In addition, we chose the right leg of each control as a reference leg. We then used the Mann-Whitney U test to compare FNBMD of these three groups of legs and searched for the factors associated with FNBMD using stepwise multiple regression analyses.

RESULTS

Compared to the reference leg, men with polio had significantly lower FNBMD in both their longer and shorter legs, by 13% and 23%, respectively. The difference in FNBMD between the two legs of polio subjects was significant. Knee extensor strength and regular exercise were two important factors associated with bilateral FNBMD in men with polio.

CONCLUSIONS

Men with polio had lower bilateral FNBMD. FNBMD of the shorter leg should be the choice for predicting the risk of hip fracture in men with polio because on average, the shorter leg has lower BMD.

No difference in gender-specific hip replacement outcomes

Gender-specific total hip arthroplasty (THA) design has been recently debated with manufacturers launching gender-based designs. The purpose of this study was to investigate the survivorship and clinical outcomes of a large primary THA cohort specifically assessing differences between genders in clinical outcomes, implant survivorship, revisions as well as sizing and offset differences. We reviewed 3461 consecutive patients receiving 4114 primary THAs (1924 women, 1537 men) between 1980 and 2004 with a minimum of 2 years followup (mean, 11.33 +/- 6.5 years). A subset of patients with complete implant data was reviewed for sizing and offset differences. Preoperative, latest, and change in clinical outcome scores as well as Kaplan-Meier analysis were performed. Men had higher raw clinical outcome scores preoperatively and postoperatively. Differences in change of clinical outcome scores were found only in the WOMAC pain score in favor of the female cohort (39.4 versus 36.1). Survivorship and revision rate were not significantly different. Men used larger stems with greater stem lengths, neck offset, and neck lengths. Current implant systems were sufficiently versatile to address the different size and offset needs of male and female patients. These data suggest there is no apparent need for a gender-designed THA system.

LEVEL OF EVIDENCE

Level II, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.

A nationwide seven-year trend of hip fractures in the elderly population of Taiwan

To investigate the recent longitudinal trend of hip fractures (including cervical and trochanteric fractures) in Taiwan's elderly population (> or =65 years), a nationwide descriptive epidemiological study was conducted using the database of the Bureau of National Health Insurance from 1996 through 2002. Frequencies and incidences of hip fracture by gender, fracture site, and age group were estimated, and the 7-year incidence trend was further evaluated. The results showed that a total of 75,482 hip fractures occurred during the study period with an incidence rate of 57.54 per 10,000 per year. Overall incidence significantly increased by 30% (p<0.0001), from 49.56 to 64.37 per 10,000 per year during the 7-year study period. The increase in rates was greater in males (36%) than in females (22%). The average female-to-male ratio was 1.76, lower than those in many countries. In females, the annual incidence of cervical fracture was higher than that of trochanteric fractures throughout the 7 years, while the incidence of trochanteric fractures was higher than cervical fractures each year in males (p<0.0001). The average annual incidence of patients older than 85 years was 9.9 times higher than that of aged 65 to 69 years in females and 7.9 times in males. Development and implementation of public health strategies for hip fractures should more focus on these subgroups in Taiwan's rapidly aging society.

Bone mineral density changes during the menopause transition in a multiethnic cohort of women

CONTEXT

Rates of bone loss across the menopause transition and factors associated with variation in menopausal bone loss are poorly understood.

OBJECTIVE

Our objective was to assess rates of bone loss at each stage of the transition and examine major factors that modify those rates.

DESIGN, SETTING, AND PARTICIPANTS

We conducted a longitudinal cohort study of 1902 African-American, Caucasian, Chinese, or Japanese women participating in The Study of Women's Health Across the Nation. Women were pre- or early perimenopausal at baseline.

OUTCOME MEASURE

We assessed bone mineral density (BMD) of the lumbar spine and total hip across a maximum of six annual visits.

RESULTS

There was little change in BMD during the pre- or early perimenopause. BMD declined substantially in the late perimenopause, with an average loss of 0.018 and 0.010 g/cm2.yr from the spine and hip, respectively (P<0.001 for both). In the postmenopause, rates of loss from the spine and hip were 0.022 and 0.013 g/cm2.yr, respectively (P<0.001 for both). During the late peri- and postmenopause, bone loss was approximately 35-55% slower in women in the top vs. the bottom tertile of body weight. Apparent ethnic differences in rates of spine bone loss were largely explained by differences in body weight.

CONCLUSIONS

Bone loss accelerates substantially in the late perimenopause and continues at a similar pace in the first postmenopausal years. Body weight is a major determinant of the rate of menopausal BMD loss, whereas ethnicity, per se, is not. Healthcare providers should consider this information when deciding when to screen women for osteoporosis.

One-year soy isoflavone supplementation prevents early postmenopausal bone loss but without a dose-dependent effect

It is believed that soy isoflavone has much potential effectiveness on the postmenopausal status; however, the optimal dose for preventing postmenopausal bone loss still remains unclear. This open-labeled, self-controlled pilot study was undertaken to determine the effect of 1-year supplementation of different high dosages of soy isoflavone in postmenopausal Taiwanese women. Forty-three women aged 45-67 years were enrolled and randomly assigned into a control (C), 100 mg/day isoflavone (IF100) and 200 mg/day isoflavone (IF200) groups for 1 year. Dual-energy X-ray absorptiometry and other related biochemical markers of bone metabolism were measured. Results indicated that the decrease in bone mineral density (BMD) was significant for lumbar vertebrae L1-3, L1-4 and the femur neck in the C group; surprisingly, the BMD of L1-3 was significantly elevated in the IF100 group; however, there were no consistent responses in the IF200 group. No significant change except loss of the bone mineral content of Ward's triangle (P=.003) was found in the IF200 group after treatment. The percentage change at L1-3 was less (P=.04) in the IF200 group when compared to the IF100 group. A relatively uniform direction of bone formation in expanding the weight and area with different rates of change resulted in different BMD changes. Both indicated a change of bone formation patterns with the higher-dose supplement. A protective effect of IF100 on estrogen-related bone loss was observed. A lack of a benefit such as high safety in the IF200 group for 1-year administration was ensured and lacked undesirable side effects.

Bone health of immigrant Chinese women living in New York City

Osteoporosis is a serious national and global public health problem, but data on bone health are limited for Asian women living in the U.S., the majority of whom are Chinese. For this study, we measured bone mineral density (BMD) by dual energy X-ray densitometry (DXA) at the lumbar spine and hip region in 300 immigrant Chinese women, ages 40-90 y, living in New York City. We also collected demographic and health data, information about knowledge and care for osteoporosis, and anthropometric measures, and estimated calcium intake from the women. In our sample, 55% had osteoporosis and 38% had low bone mass (osteopenia). Older age, lower body mass index (BMI), and shorter height were associated with lower BMD at all sites. Years lived in the U.S. and number of children were also associated with lower BMD of the lumbar spine. Chinese women who emigrated from Mainland China had lower BMD at the lumbar spine and femoral neck than Chinese women who emigrated from Hong Kong, after adjusting for potential confounders. Both groups of immigrant women had lower BMD at all sites than a national sample of U.S. Caucasian women. Although the women in our study had generally poor knowledge about osteoporosis, most could identify at least one food rich in calcium. The large number of immigrant Chinese women in New York City with osteoporosis calls for major efforts to increase awareness, prevention, diagnosis, and treatment of this condition in this susceptible population.

Structural and biomechanical basis of sexual dimorphism in femoral neck fragility has its origins in growth and aging

The structural basis for sex differences in femoral neck (FN) fragility was studied in 1196 subjects and 307 patients with hip fracture. The absolute and relative patterns of modeling and remodeling on the periosteal and endocortical envelopes during growth and aging produce changes in FN geometry and structure that results in FN fragility in both sexes and sexual dimorphism in hip fracture risk in old age.

INTRODUCTION

Femoral neck (FN) fragility in old age is usually attributed to age-related bone loss, while the sex differences in hip fracture rate are attributed to less bone loss in men than in women. The purpose of this study was to define the structural and biomechanical basis underlying the increase in FN fragility in elderly men and women and the structural basis of sex differences in hip fracture incidence in old age.

MATERIALS AND METHODS

We measured FN dimensions and areal bone mineral density in 1196 healthy subjects (801 females) 18-92 years of age and 307 patients (180 females) with hip fracture using DXA. We then used the DXA-derived FN areal bone mineral density (BMD) and measured periosteal diameter to estimate endocortical diameter, cortical thickness, section modulus (a measure of bending strength), and buckling ratio (indices for structural stability).

RESULTS

Neither FN cortical thickness nor volumetric density differed in young adult women and men after height and weight adjustment. The sex differences in geometry were confined to the further displacement of the cortex from the FN neutral axis in young men, which produced 13.4% greater bending strength than in young women. Aging amplified this geometric difference; widening of the periosteal and endocortical diameters continued in both sexes but was greater in men, shifting the cortex even further from the neutral axis maintaining bending strength in men, not in women. In both sexes, less age-related periosteal than endocortical widening produced cortical thinning increasing the risk for structural failure by local buckling of the enlarged thin walled FN. Relative to age-matched controls, women and men with hip fractures had reduced cortical thickness, but FN periosteal diameter was increased in women and reduced in men, differences are likely to be originated in growth.

CONCLUSIONS

The absolute and relative patterns of modeling and remodeling on the periosteal and endocortical envelopes during growth and aging produce changes in FN diameters, cortical thickness, and geometry that results in FN fragility in both sexes and sexual dimorphism in hip fracture risk in old age.

Ultradistal and distal forearm bone mineral density in postmenopausal women

OBJECTIVES

A cross-sectional study was conducted to evaluate bone mineral density of the forearm in older women.

METHODS

Eight hundred and thirty-two women who had received a routine distal forearm bone mineral density screening measurement were included. Data were collected on age, age at menopause, duration of menopause, body height, body weight, and duration of hormone replacement therapy.

RESULTS

After menopause the incidence of osteoporosis increased markedly with age, from 5.8% in the distal site and 3.9% in the ultradistal site less than 5 years after menopause to 61.1% and 44.4%, respectively, 25 years or later after menopause. Hormone replacement therapy markedly reduced the incidence of osteoporosis.

CONCLUSIONS

After menopause, the incidence of osteoporosis in the forearm increased markedly with years. Women with higher body weight had higher forearm bone mineral density, and postmenopausal hormone replacement therapy prevented bone loss in the forearm.

Sexual dimorphism in vertebral fragility is more the result of gender differences in age-related bone gain than bone loss

Spine fractures usually occur less commonly in men than in women. To identify the structural basis for this gender difference in vertebral fragility, we studied 1013 healthy subjects (327 men and 686 women) and 76 patients with spine fractures (26 men and 50 women). Bone mineral content (BMC), cross-sectional area (CSA), and volumetric bone mineral density (vBMD) of the third lumbar vertebral body (L3) were measured by posteroanterior (PA) and lateral scanning using dual-energy X-ray absorptiometry (DXA). In this cross-sectional study, the diminution in peak vertebral body BMC from young adulthood to old age was less in men than in women (6% vs. 27%). This diminution was the net result of two opposing changes occurring concurrently throughout adult life: the removal of bone adjacent to marrow on the inner (endosteal) surface by bone resorption and the deposition of bone on the outer (periosteal) surface by bone formation. For L3, we estimated that men resorbed 3.7 g and deposited 3.1 g, producing a net loss of 0.6 g from young adulthood to old age and women resorbed 3.1 g and deposited only 1.2 g, producing a net loss of 1.9 g. Thus, based on our indirect estimates of periosteal gain and endosteal loss across life, the observed net diminution in BMC during aging was less in men than women because absolute periosteal bone formation was greater in men than women (3.1 g vs. 1.2 g) not because absolute bone resorption was less in men. On the contrary, the absolute amount of bone resorbed was greater in men than women (3.7 g vs. 3.1 g). Periosteal bone formation also increased vertebral body CSA 3-fold more in men than in women, distributing loads onto a larger CSA, so that the load imposed per unit CSA decreased twice as much in men than in women (13% vs. 5%). In men and women with spine fractures, CSA and vBMD were reduced relative to age-matched controls. However, vBMD was no different to the adjusted vBMD in age-matched controls derived assuming controls had no periosteal bone formation during aging. Thus, large amounts of bone are resorbed in men as well as in women, accounting for the age-related increase in spine fractures in both genders. Periosteal bone formation increases CSA and offsets bone loss in both genders but more greatly in men, accounting for the lower incidence of spine fractures in men than in women. We speculate that reduced periosteal bone formation, during growth or aging, may be in part responsible for both reduced vertebral size and reduced vBMD in men and women with spine fractures. Sexual dimorphism in vertebral fragility is more the result of gender differences in age-related bone gain than age-related bone loss.

Phytoestrogens and healthy aging: gaps in knowledge. A workshop report

There is an increasing public interest in foods and dietary supplements containing phytoestrogens for the maintenance of health. A workshop was convened to assess evidence for the potential benefits of phytoestrogen-containing foods or supplements on diseases or conditions affecting older populations. Preclinical, clinical, and epidemiologic data on the cardiovascular system, various cancers, bone diseases, and menopausal symptoms were the focus of the discussions. Research on the basis of consumer food choices as well as a presentation from the FDA regarding approval of the use of soy foods to reduce the risk of cardiovascular disease were also presented. Based on the information presented, isoflavone-containing soy foods may have favorable effects on the cardiovascular system, but major knowledge gaps still exist regarding effects ofphytoestrogen supplements on bone diseases, various cancers, menopausal symptoms, and cognitive function.

Body composition characteristics are associated with the bone density of the proximal femur end in middle- and old-aged women and men

OBJECTIVES

In the present study the associations between bone density of the proximal femur end and weight status, fat distribution patterns (FDI) and body composition parameters i.e. amount of body fat and lean body mass were tested in a sample of old aged women and men.

METHODS

In 77 healthy women ranging in age from 60 to 92 years (x=71.8 years) and 62 healthy men ranging in age from 60 to 86 years (x=71.5 years) the bone mineral density (BMD of the proximal femur end and the body composition parameters absolute fat mass, relative fat mass, lean body mass and bone mineral content were estimated by dual energy X-ray absorptiometry. Additionally, the weight status (body mass index, BMI) and the FDI were calculated. The bone density of the proximal femur end was correlated with the absolute fat mass and the lean body mass as well as with the BMI and the FDI.

RESULTS

BMD correlated in females significantly positively with parameters of body composition, in males no significant correlations between fat mass (absolute and relative) and BMD as well as BMD/stature was found. Furthermore, it was shown that the weight status (BMI; r(2)=0.13, P<0.0003 in males and r(2)=0.27, P<0.000 in females), and the lean body mass (r(2)=0.21, P<0.001 in males, r(2)=0.36, P<0.004 in females) were associated significantly positively with the BMD of the proximal femur end in both sexes. The absolute fat mass had a significant impact on BMD in the female subsample only (r(2)=0.24, P<0.000).

CONCLUSIONS

A lower weight status and a low amount of lean body mass, indicating not only lack of biomechanical forces of the proximal femur end, but also a lack of physical activity can be assumed to be associated increased bone loss and the development of osteoporosis in both sexes. An association between low amount of fat tissue and decreased BMD was especially found in women and may be due to the reduced conversion rates from androgens to estrogens in a low amount of fat tissue.

Fracture site-specific deficits in bone size and volumetric density in men with spine or hip fractures

To study the structural basis of bone fragility in men, we compared bone size and volumetric bone mineral density (vBMD) of the third lumbar vertebra and femoral neck in 95 men with spine fractures, 127 men with hip fractures, and 395 healthy controls using dual-energy X-ray absorptiometry (DXA). The results were expressed in absolute terms and age-specific SD scores (mean +/- SEM). In controls, vertebral body and femoral neck width increased across age, being 0.46 +/- 0.11 SD and 0.91 +/- 0.08 SD higher in elderly men than in young men, respectively (both,p < 0.001). Men with spine fractures had reduced vertebral body width (-0.45 +/- 0.10 SD;p < 0.01) but not femoral neck width (-0.15 +/- 0.10 SD, NS). Men with hip fractures had reduced femoral neck width (-0.45 +/- 0.11 SD; p < 0.01) and vertebral body width (-0.25 +/- 0.10 SD; p < 0.05). The deficits in bone volume (BV) exaggerated the deficits in bone mineral content (BMC) by 40% at the vertebrae in men with spine fractures and by 9% at the femoral neck in men with hip fractures. vBMD deficits were greater at the vertebrae in men with spine fractures than in men with hip fractures (-1.37 +/- 0.08 SD vs.-0.70 +/- 0.10 SD, respectively; p < 0.01) but were similar at the femoral neck (-0.93 +/- 0.10 SD and -0.76 +/- 0.11 SD, respectively, NS), despite the men with spine fracture being 10 years younger. Bone fragility leading to spine or hip fractures in men may be the result of fracture site-specific deficits in bone size and vBMD that have their origins in growth, aging, or both.

Effects of alendronate on osteopenic postmenopausal Chinese women

To evaluate the effects of alendronate on postmenopausal Chinese women with osteopenia, we treated 46 subjects daily with either 10 mg alendronate (N = 24) or placebo plus 500 mg calcium supplement (N = 22), and measured their bone mineral density (BMD) at the lumbar spine and hip, and urinary bone resorption markers before, during, and after the 1 year treatment period. The bone markers included N-telopeptide of type I collagen (NTx) and deoxypyridinoline (Dpd); both were corrected by the concentration of creatinine in the same sample (NTx/Cr and Dpd/Cr). Both NTx/Cr and Dpd/Cr decreased significantly by 44% and 28%, respectively (p < 0.05 for both), in 1 month in the active treatment group but did not change in the placebo group. BMD at the spine, femoral neck, trochanter, and Ward's triangle increased significantly by 6 months and showed a further increase through month 12 at the spine in the alendronate-treated group. Relative to the placebo group, BMD changes at various sites in the alendronate-treated group were higher at 12 months by 6%-11%. Thus, our data suggest that 10 mg alendronate daily resulted in significant increases in spine and hip BMD, and decreases of urinary resorption markers in the osteopenic postmenopausal Chinese women studied. The amplitude of responses was higher than in previous reports in the USA and Europe.

Effect of bone area on spine density in Chinese men and women in Taiwan

Areal bone mineral density (BMD), the quotient of bone mineral content (BMC) divided by the projectional bone area (BA), measured with dual-energy X-ray absorptiometers (DXA), is the most common parameter used today to evaluate spinal osteoporosis. To evaluate whether gender, age, weight, and height can determine spinal BA, and to compare BA and analyze its effects on spinal density in the two genders, we measured BA and BMC, and calculated areal BMD, and the bone mineral apparent density (BMAD = BMD/the square root of BA) of the L-2 to L-4 vertebrae of 604 female and 223 male Chinese volunteers from 20 to 70 years of age using a Norland XR-26 DXA. Standardized for height and weight, BA showed a relatively large variation and a significant increase with increasing age in both genders. On the other hand, BMC stayed unchanged in men > 50 years of age and decreased with aging in postmenopausal women. Younger men (< 51 years) had a much larger mean BA (by 15.5%) and larger mean BMC (only 10%) than that of age-matched women. As a result, younger men had a slightly and significantly lower areal BMD (by 7.1%) and a much lower BMAD (by 16%) (p < 0.0001 for both) than premenopausal women of similar age. Men had higher areal BMD and BMAD values than age-matched women only after age 50 years. Although taller body height, heavier weight, and increasing age were associated with a larger BA, these factors could not explain most of the interindividual variations in BA in both genders. Thus anteroposterior BA of lumbar vertebrae measured with DXA seems to affect the areal BMD and BMAD readings in the two genders. The larger BA caused a low BMAD and probably underestimated the true volumetric spine density in men.