Changes in Bone Mineral Density During Pregnancy and Postpartum: Prospective Data on Five Women

Areal bone mineral density (BMD, g/cm²) of five healthy women (aged 26–30 years) was measured at the lumbar spine, right femoral neck and dominant distal radius with dual-energy X-ray absorptiometry before pregnancy, immediately after delivery, 1 month after the resumption of menses and 1 year thereafter. Because of the small number of subjects, only individual changes in BMD that were greater than 2√2 times the short-term in vivo precision were considered as significant changes. To obtain a further perspective, the reproduction-related BMD changes were compared with twice the standard deviation (SD) of the BMD changes in healthy premenopausal women (about ± 5%), and with the SD of the BMD in a cross-sectional sample of young healthy women. The duration of postpartum amenorrhea (PPA) and of lactation in our subjects ranged from about 2 months to 1 year and from 5 months to almost 2 years, respectively. No clear association between PPA and lactation could be seen. The magnitudes of reproduction-related BMD changes in general seemed not to differ substantially from about ± 5% variability in BMD changes in healthy nonpregnant and nonlactating women. There was, however, some tendency toward systematic bone loss at the lumbar spine (about –3%) during pregnancy and at the femoral neck during PPA (about –5% as compared with prepregnancy data). Some individuals can yet show large, systematic bone losses comparable to 1 SD in magnitude. The site-specific reproduction-induced bone loss and consequent recovery are apparently multifactorial phenomena that may be related not only to duration and magnitude of lactation and/or duration of postpartum amenorrhea, but also to prevailing biomechanical and dietary factors, and other yet unknown individually modulated factors. Received: 31 March 1998 / Accepted: 25 November 1998     

Household Tobacco Smoke Exposure is Negatively Associated with Premenopausal Bone Mass

Subjects exposed to environmental tobacco smoke have been found to be at increased risk for several health problems. Whether exposure to passive tobacco smoke is associated with reduced bone mineral density (BMD) is unknown. In order to examine this, we measured BMD in 154 healthy premenopausal women (age range 40–45 years). BMD of the total hip, femoral neck, lumbar spine and total body was measured by dual-energy X-ray absorptiometry (DXA). Data were collected on exposure to household tobacco smoke from age 10 years to the present as well as on other lifestyle factors related to bone mass. We found that 67.5% of the subjects had a history of household tobacco smoke exposure. Subjects exposed to household tobacco smoke had a mean adjusted BMD that was significantly lower at the total hip (p= 0.021) and femoral neck (p= 0.018) compared with subjects who were not exposed. In addition, duration of household tobacco smoke exposure was negatively associated with BMD at the total hip (p = 0.010), femoral neck (p= 0.004), lumbar spine (p = 0.037) and total body (p = 0.031). Subjects exposed to household tobacco smoke for 15 years or more had mean adjusted BMD that was 4% lower at the total body, and more than 8% lower at the total hip, femoral neck and lumbar spine, compared with subjects who were not exposed. In conclusion, household tobacco smoke exposure during adolescence and young adulthood was found to be negatively associated with BMD at the total hip and femoral neck, and duration of exposure was negatively associated with BMD at the total hip, femoral neck, lumbar spine and total body in premenopausal women. Received: 17 December 2001 / Accepted: 16 February 2002     

Identification of Women with Reduced Bone Density at the Lumbar Spine and Femoral Neck using BMD at the Os Calcis

We assessed the clinical usefulness of bone density measurements at the os calcis as a screening tool to identify patients with low bone density at the lumbar spine and femoral neck. Bone mineral density (BMD) was recorded in 443 women (mean age 60 years) referred to a bone densitometry service. Measurements were made at the lumbar spine and femoral neck using a Lunar DPXL and at the right os calcis using a Peripheral Instantaneous X-ray Imaging (PIXI) dual-energy X-ray absorptiometry system. Average T-scores derived using the manufacturer”s data were: 1.59 for the lumbar spine, −1.41 for the femoral neck and −0.87 for the os calcis. The prevalence of osteoporosis using WHO criteria (T-scores of −2.5 or less) was 36% for the lumbar spine or femoral neck but only 9.7% for the os calcis. BMD of the os calcis correlated with that at the lumbar spine (r= 0.69, p<0.001) and femoral neck (r= 0.67, p<0.001). The area under the receiver operator characteristics curve was 0.836 (standard error 0.020) for the os calcis related to osteoporosis at the lumbar spine or femoral neck. Optimal accuracy was obtained at a T-score of ≤−1.3 (BMD 0.39 g/cm²) when the sensitivity was 69.6% (95% confidence interval 65.3, 73.9%) and specificity 82.6% (95% confidence interval 79.1, 86.1%). However, the probability of diagnosing low bone density from a given BMD at the os calcis varied by age and site scanned. Accordingly, for informing management strategies, the choice of a single cutoff BMD at the os calcis may not be appropriate and several thresholds may be adopted based on age, the site of interest (lumbar spine or femoral neck) and consideration of associated clinical features. Thus, the use of heel bone density scanners could reduce the number of axial bone density measurements required. The advantages of portability, low cost and shorter scan times should reduce the cost of detection and provide a greater opportunity for identification of women at risk of fracture. Received: 18 June 1999 / Accepted: 30 March 2000     

A Prospective Study of Bone Loss in Menopausal Australian-Born Women

Two hundred and twenty-four women (74 pre-, 90 peri-, 60 post-menopausal), aged 46–59 years, from a population-based cohort participated in a longitudinal study of bone mineral density (BMD). BMD was measured by dual-energy X-ray absorptiometry (DXA) at the lumbar spine and femoral neck and the time between bone scans was on average 25 (range 14–41) months. The aim of the study was to assess changes in BMD in relation to changes in normal menopausal status. During the study period women who were between 3 and 12 months past their last menstrual period (n= 22, late perimenopausal) at the time of the second bone scan had a mean (SE) annual change in BMD of 70.9% (0.4%) at the lumbar spine and 70.7% (0.6%) at the femoral neck (both p50.05 compared with women who remained premenopausal). In the women who became postmenopausal (n= 42) the mean annual changes in BMD were 72.5% (0.2%) at the lumbar spine and 71.7% (0.2%) at the femoral neck (both p50.0005), and in the women who remained postmenopausal (n= 60) they were 70.7% (0.2%) per year and 70.5% (0.3%) per year respectively (both p50.05), compared with women who remained premenopausal. In the 1–3 years after the final menstrual period (FMP) there was greater bone loss from the lumbar spine than the femoral neck (p50.05). In women who were menstruating at the time of the second bone scan and whose FMP could be dated prospectively (n= 35), higher baseline oestradiol levels were associated with less lumbar spine bone loss (p50.005). In the women who remained postmenopausal there was an association between baseline body mass index (BMI) and percentage change per year in femoral neck BMD (p50.05), such that women with higher BMI had less bone loss. In conclusion, during the time of transition from peri- to post-menopause, women had accelerated BMD loss at both the hip and spine. Received: 23 June 1997 / Accepted: 5 November 1997     

Pregnancy and Lactation Confer Reversible Bone Loss in Humans

The influence of pregnancy on bone mineral density (BMD) was evaluated by dual-energy X-ray absorptiometry (DXA) in 73 women (mean age 29 years, range 20–44 years) postpartum. Fifty-five age-matched women served as controls. The influence of lactation was evaluated in 65 of the delivered women who were followed with repeated measurements, a mean of 4.5 ± 0.1 and 11.5 ± 0.1 months after the delivery. The influence of multiple pregnancies was evaluated in 39 premenopausal women (mean age 38 years, range 31–54 years) with a minimum of four pregnancies (range 4–7). Fifty-eight age-matched healthy premenopausal women with a maximum of two pregnancies (range 0–2) served as controls. Data are presented as mean ± SEM. BMD data are adjusted for differences in total fat mass and total lean mass. Lumbar spine BMD was 7.6 ± 0.1% and total body BMD 3.9 ± 0.1% lower in women postpartum compared with controls (both p<0.001). BMD did not decrease significantly in non-breastfeeding mothers. Mothers breastfeeding for 1–6 months decreased femoral neck BMD by 2.0 ± 1.0% during the first 5 months postpartum (p<0.001). No further BMD loss was seen between 5 and 12 months postpartum. Femoral neck BMD 12 months after delivery was 1.3 ± 0.8% lower than after delivery in mothers breastfeeding for 1–6 months (p= 0.05). Mothers breastfeeding for more than 6 months decreased Ward’s triangle BMD by 8.5 ± 1.0% and lumbar spine BMD by 4.1 ± 0.8% during the first 5 months postpartum (both p<0.05). No further BMD loss was seen between 5 and 12 months postpartum. Femoral neck BMD 12 months after delivery was 4.0 ± 1.1% lower and Ward’s triangle BMD 5.3 ± 1.9% lower than after delivery in mothers breastfeeding for more than 6 months (both p<0.05). BMD loss was higher during the first 5 months following delivery in the lactating women compared with the non-lactating women (p< 0.05 comparing lumbar spine BMD loss in lactating mothers versus non-lactating mothers). However, in women with a minimum of four pregnancies the BMD was no lower than in age-matched women with fewer pregnancies. Total duration of lactation was not correlated with the present BMD. In summary, pregnancy seem to confer a low BMD with additional BMD loss during 5 months of lactation. Even if complete restoration in BMD was not reached within 5 months of weaning, women with four pregnancies or more had a BMD no lower than women with two pregnancies or fewer. We conclude that neither an extended lactation period nor multiple pregnancies could be used as a risk factor when predicting women at risk for future osteoporosis. Received: 15 November 2000 / Accepted: 21 March 2001     

Vitamin D and Estrogen Receptor Polymorphisms and Bone Mineral Changes in Postpartum Women

BsmI restriction fragment length polymorphism (RFLP) of the vitamin D receptor (VDR) gene and PvuII RFLPs of the estrogen receptor (ER) gene and their relation to changes in areal bone mineral density (BMD) were examined in 43 healthy postpartum Finnish women aged 31.3 (SD 4.7) years. BMD was measured by dual energy X-ray absorptiometry at lumbar spine, right femoral neck, and dominant distal radius immediately after delivery, 1 month after resumption of menses, and 1 year thereafter. The RFLPs were represented as Bb (BsmI) and Pp (PvuII), the capital letters denoting the absence of and the small letters the presence of the restriction sites. The frequency of VDR alleles was as follows: bb (20.9%), Bb (60.5%), and BB (18.6%), and that of ER alleles was pp (39.5%), Pp (51.2%), and PP (9.3%). Altogether, BMD decreased significantly during postpartum amenorrhea at all sites [the mean bone loss ranging from −1.2 (SD 3.6)% at the distal radius to −3.7 (2.9)% at the femoral neck], and increased after resumption of menses [the 1-year follow-up BMD values ranging from −1.0 (2.4)% at the femoral neck to +3.3 (4.0)% at the lumbar spine as compared with baseline]. No obvious genotype-related differences were found between these changes. These results suggest that the BsmI and PvuII polymorphisms may not have substantial influence on BMD changes postpartum. Received: 20 November 1998 / Accepted: 30 September 1999     

Bone Density in an Immigrant Population from Southeast Asia

The epidemiology of bone loss in populations of Asian heritage is still poorly known. This study compared the skeletal status of a convenience sample of 396 Southeast Asian immigrants (172 Vietnamese, 171 Cambodians and 53 Laotians) residing in Rochester, Minnesota in 1997 with 684 white subjects previously recruited from an age-stratified random sample of community residents. Areal bone mineral density (BMD, g/cm²) and volumetric bone mineral apparent density (BMAD, g/cm³) were determined for lumbar spine and proximal femur using the Hologic QDR 2000 instrument for the white population and the QDR 4500 for Southeast Asian subjects; the machines were cross-calibrated from data on 20 volunteers. Lumbar spine BMD was 7% higher in white than Southeast Asian women ( p < 0.001), and similar results were observed for the femoral neck; lumbar spine BMD was 12% higher in white than nonwhite men ( p < 0.001). Race-specific discrepancies were reduced by calculating BMAD: for premenopausal women, lumbar spine and femoral neck differences between whites and Southeast Asians were eliminated; for postmenopausal women the lumbar spine differences persisted ( p < 0.0001), while femoral neck BMAD was actually higher for Southeast Asians. There were no race-specific differences in femoral neck BMAD among men of any age ( p= 0.312), but lumbar spine BMAD was less for younger ( p= 0.042) but not older ( p= 0.693) Southeast Asian men. There were differences among the Southeast Asian subgroups, but no clear pattern emerged. Predictors of lumbar spine BMAD in Southeast Asian women were age ( p < 0.001), weight ( p= 0.015) and gravidity ( p= 0.037). Even after adjusting for bone size using BMAD, 32% and 9% of Southeast Asian women and men, respectively, would be considered to have osteoporosis at the femoral neck and 25% and 4%, respectively, at the lumbar spine. These findings indicate a need for culturally sensitive educational interventions for Southeast Asians and for physicians to pursue diagnosis and treatment to prevent osteoporosis-related disabilities in this population. Received: 12 October 2000 / Accepted: 15 February 2001     

An Investigation of the Diagnostic Value of Bilateral Femoral Neck Bone Mineral Density Measurements

This paper describes a study to assess the clinical value of bilateral femoral neck bone mineral density (BMD) measurements. Although a range of factors will determine clinical decisions, the classification of the site with the lowest T-score is likely to have significant bearing on the management of a patient. While it is common practice to measure BMD at the lumbar spine and a single neck of femur, knowledge of the BMD of the second femur may also be of diagnostic value. Using dual-energy X-ray absorptiometry, BMD of the lumbar spine and right and left femoral neck was measured in a group of 2372 white, Caucasian women (mean age ± SD, 56.6 ±13.9 years) routinely referred for bone densitometry. Analysis of the measurements showed a significant (p= 0.02) but small difference between the mean BMD of the right (0.840 ± 0.152 g/cm²) and left (0.837 ± 0.150 g/cm²) femoral neck. Further investigation of femur scans revealed 79 (3.3%) patients in whom one side was osteoporotic while the other side and spine were normal or osteopenic using the World Health Organization diagnostic criteria in combination with manufacturer”s reference data. Patients in whom the femoral neck BMD measurements differed by less than the precision error of the system were then excluded. This left only 51 (2.2%) patients, that is 29 (1.2%) for right femur and spine scan and 22 (0.9%) for left femur and spine scan, in whom knowledge of both femoral neck BMD measurements could have altered the classification of the lowest site assessed to osteoporotic. These data suggest that there is only a small benefit from performing bilateral femoral neck BMD measurements. Since BMD measurements are only one of a range of factors considered as part of a patient”s management, it is suggested that the extra time, cost and radiation dose associated with measurement of the second femur may not be justified. Received: 28 October 1999 / Accepted: 2 February 2000     

Vitamin D and Bone Mineral Density in Ambulatory Women Living in Buenos Aires, Argentina

The aim of this study was to determine possible associations between bone mineral density (BMD), 25-hydroxyvitamin D (25(OH)D) and intact parathyroid hormone (PTH). In a retrospective study we examined the case notes of free-living postmenopausal women living in our city (34° S). We also report a low prevalence of vitamin D deficiency (25(OH)D <25 nmol/l, 5.6%) and of secondary hyperparathyroidism (intact PTH >65 pg/ml, 7.5%). Age was correlated with BMD at the lumbar spine (r=−0.25, p = 0.00038) and femoral neck (r=−0.252, p = 0.0003). Body mass index (BMI) was correlated with BMD at the femoral neck (r= 0.177, p = 0.021) but not at the lumbar spine. 25(OH)D was positively correlated with BMD at the femoral neck (r = 0.149, p=0.036) but not at the lumbar spine. PTH was positively correlated with age (r= 0.279, p = 0.012) and negatively correlated with 25(OH)D (r=−0.322, p = 0.0036). PTH was also negatively correlated with BMD at the lumbar spine (r=−0.258, p=0.02) and the femoral neck (r=−0.282, p = 0.011). Forward stepwise multiple regression showed that BMI, age and 25(OH)D made significant contributions to BMD at the femoral neck. PTH also showed a significant contribution to BMD at both sites. In conclusion, weak correlations found between PTH and 25(OH)D and BMD suggest these biochemical variables, among other factors, contribute to lumbar spine and femoral neck BMD. Received: 19 February 2000 / Accepted: 20 June 2000     

Variations in Bone Density among Persons of African Heritage

The epidemiology of bone loss in populations of African heritage is still poorly known. We compared a convenience sample of 47 African-American (AA) residents of Rochester, Minnesota (32 women, 15 men) and 66 recent immigrants from Somalia (all women) with 684 white subjects (349 women, 335 men) previously recruited from an age-stratified random sample of community residents. Areal bone mineral density (BMD, g/cm²) and volumetric bone mineral apparent density (BMAD, g/cm³) were determined for lumbar spine and proximal femur using the Hologic QDR 2000 for white subjects and the QDR 4500 for the others; the instruments were cross-calibrated from data on 20 volunteers. Lumbar spine BMD was 18% higher in AA (p<0.001) and 4% lower in Somali (p= 0.147) than white women. Femoral neck BMD was 27% higher in AA women but also 11% greater in Somali women (both p<0.001) compared with whites. Lumbar spine BMD was 6% higher (p= 0.132) and femoral neck BMD 21% higher (p<0.001) in AA than white men. No Somali men were studied. After correcting for bone size differences, both lumbar spine (p<0.01) and femoral neck BMAD (p<0.001) were greater for Somali than white women, but the difference between Somali and AA women persisted. Lumbar spine and femoral neck BMAD values also remained significantly greater for AA women (both p<0.001) and men (p<0.05; p<0.001) compared with whites. Weight was associated with BMAD at both skeletal sites in all groups, but adjustment for differences in weight did not reduce the discrepancy in BMAD values between Somali and AA women or between the latter group and whites. This heterogeneity among different ethnic groups of African heritage may provide an opportunity for research to better explain race-specific differences in bone metabolism. Received: 4 September 2001 / Accepted: 11 January 2002     

Premature Greying of the Hair Is Not Associated with Low Bone Mineral Density

In two recent case–control studies premature greying of the hair was associated with a lowering of bone mineral density (BMD) and osteopenia, suggesting that this might be a clinically useful risk marker for osteoporosis. We report a further re-examination of this proposal in 52 prematurely grey-haired women from East Yorkshire who responded to an advertisement inviting them for bone densitometry. Thirty-five had no clinical or drug history that could influence bone density. All were Caucasian with a mean age of 52.8 years. In the group as a whole the mean BMD values at the lumbar spine and femoral neck were no different from those of a young adult, but there was a trend toward a greater than average BMD than that of the local age-matched population (p= 0.097 and 0.218, respectively). Twenty women were premenopausal, with an average age of 45.3 years. Mean BMD values at the lumbar spine and femoral neck in this group were no different from those of young adults. There was, however, a trend toward a BMD greater than that of the local age-matched population at the femoral neck (p= 0.117). Fifteen women were postmenopausal with an average age of 62.9 years and an average age at menopause of 51.1 years. Mean BMD values at both the lumbar spine and femoral neck in this group were lower than those of young adults, but no different from those of the local age-matched population. In conclusion, our group of prematurely grey-haired women had average BMD for their age, and we are therefore unable to support the proposed clinical usefulness of premature greying as a risk marker for osteoporosis. Received: 1 December 1998 / Accepted: 11 March 1999     

Regular Physical Exercise and Bone Mineral Density: A Four-Year Controlled Randomized Trial in Middle-aged Men. The DNASCO Study

The aim of the study was to investigate the effects of regular aerobic exercise training on bone mineral density (BMD) in middle-aged men. A population based sample of 140 men (53–62 years) was randomly assigned into the exercise and reference groups. BMD and apparent volumetric BMD (BMD_vol) of the proximal femur and lumbar spine (dual-energy X-ray absorptiometry, DXA) and anthropomorphic measurements were performed at the randomization and 2 and up to 4 years later. The participation rate was 97% and 94% at the second and third BMD measurements, respectively. As another indication of excellent adherence and compliance, the cardiorespiratory fitness (aerobic threshold) increased by 13% in the exercise group. The 2% decrease in the reference group is regarded as an age-related change in cardiorespiratory fitness. Regardless of the group, there was no association between the increase in aerobic threshold and change in BMD. In the entire group, age-related bone loss was seen in the femoral neck BMD and BMD_vol (p<0.01). BMD and BMD_vol values increased with age in L2–L4 (p<0.004). An increased rate of bone loss at the femoral neck was observed in men with a low energy-adjusted calcium intake (p = 0.003). Men who increased their alcohol intake during the intervention showed a decrease in the rate of bone loss at the femoral neck (p = 0.040). A decrease in body height associated with decreased total femoral BMD (r= 0.19, p = 0.04) and the change in body height was a predictor of bone loss in the femoral neck (β= 0.201). Long-term regular aerobic physical activity in middle-aged men had no effect on the age-related loss of femoral BMD. On the other hand, possible structural alterations, which are also essential for the mechanical strength of bone, can not be detected by the DXA measurements used in this study. The increase seen in lumbar BMD reflects age-related changes in the spine, thus making it an unreliable site for BMD follow-up in men. Received: August 2000 / Accepted: November 2000     

Estimation of the Prevalence of Low Bone Density in Canadian Women and Men Using a Population-Specific DXA Reference Standard: The Canadian Multicentre Osteoporosis Study (CaMos)

The Canadian Multicentre Osteoporosis Study (CaMos) is a prospective cohort study which will measure the incidence and prevalence of osteoporosis and fractures, and the effect of putative risk factors, in a random sample of 10 061 women and men aged ≥25 years recruited in approximately equal numbers in nine centers across Canada. In this paper we report the results of studies to establish peak bone mass (PBM) which would be appropriate reference data for use in Canada. These reference data are used to estimate the prevalence of osteoporosis and osteopenia in Canadian women and men aged ≥50 years. Participants were recruited via randomly selected household telephone listings. Bone mineral density (BMD) of the lumbar spine and femoral neck were measured by dual-energy X-ray absorptiometry using Hologic QDR 1000 or 2000 or Lunar DPX densitometers. BMD results for lumbar spine and femoral neck were converted to a Hologic base. BMD of the lumbar spine in 578 women and 467 men was constant to age 39 years giving a PBM of 1.042 ± 0.121 g/cm² for women and 1.058 ± 0.127 g/cm² for men. BMD at the femoral neck declined from age 29 years. The mean femoral neck BMD between 25 and 29 years was taken as PBM and was found to be 0.857 ± 0.125 g/cm² for women and 0.910 ± 0.125 g/cm² for men. Prevalence of osteoporosis, as defined by WHO criteria, in Canadian women aged ≥50 years was 12.1% at the lumbar spine and 7.9% at the femoral neck with a combined prevalence of 15.8%. In men it was 2.9% at the lumbar spine and 4.8% at the femoral neck with a combined prevalence of 6.6%. Received: 23 April 1999 / Accepted: 14 April 2000     

A Comparative Study of Computed Digital Absorptiometry and Conventional Dual-Energy X-ray Absorptiometry in Postmenopausal Women

The aim of the study was to evaluate whether computed digital absorptiometry (CDA) of the hand might be a useful screening technique for identifying patients with postmenopausal osteoporosis and to compare the results of CDA with those of dual-energy X-ray absorptiometry (DXA) of the lumbar spine and femoral neck. We studied 230 postmenopausal women (mean age 58.4 ± 7.9 years). For CDA, bone mineral density (BMD) was measured with an AccuDEXA Schick densitometer in the third middle phalanx of the nondominant hand. For DXA, BMD of the lumbar spine and upper femur was assessed using a DXA Hologic QDR-1000 densitometer. We did a comparative analysis (ANOVA) and linear correlation tests. Sensitivity and specificity of CDA and receiver operating characteristic (ROC) curves for the diagnosis of osteoporosis were calculated. The mean BMD with CDA was 0.445 ± 0.084 (T-score: −1.27 ± 1.29). The mean BMD (g/cm²) with DXA at the lumbar spine was 0.877 ± 0.166 (T-score: −1.52 ± 1.59) and 0.708 ± 0.127 at the femoral neck (T-score: −1.12 ± 1.25). BMD at the lumbar spine and femoral neck correlated positively with CDA of the hand (r= 0.66 and r= 0.65 respectively, p<0.001). When using as cut-off a T-score of −2.5, according to WHO criteria, 76 women (33%) had osteoporosis of the lumbar spine and/or femoral neck with DXA and 42 (18%) with CDA (p<0.001). The kappa score for osteoporosis was 0.33 for CDA versus spinal DXA and 0.35 for CDA versus femoral DXA. With the cut-off level used, sensitivity and specificity of CDA in detecting osteoporosis at the lumbar spine were 0.39 and 0.90, respectively; sensitivity and specificity of CDA in identifying osteoporosis at the femoral neck were 0.58 and 0.87, respectively. The positive predictive value of CDA for osteoporosis was 69% and the negative predictive value was 75%. The area under the ROC curve for osteoporosis was 0.822 ± 0.028. We conclude that: (a) CDA assessment has a moderate correlation with BMD measured by DXA at the lumbar spine and femoral neck; (b) CDA has a low sensitivity for the diagnosis of osteoporosis compared with spinal and femoral DXA; and (c) predictive values for osteoporosis at both the lumbar spine and femoral neck are acceptable. Received: September 2000 / Accepted: January 2001     

Radial Bending Breaking Resistance Derived by Densitometric Evaluation Predicts Femoral Neck Fracture

Bone mineral density (BMD) measurement by hip dual-energy X-ray absorptiometry (DXA) is considered the best predictor of osteoporotic fracture risk. BMD takes into account only in part the bone cross-sectional area that is an important determinant of both bone compression strength and of bending breaking resistance. From DXA measurements of proximal radius (Osteoplan, NIM, Verona, Italy) we obtained the projected outer diameter (D) and the mean diameter of the medulla (d), by an algorithm based on the assumption of a constant cortical volumetric density of 1050 g/cm³. The algorithm was validated by the good correlation found (r= 0.8) between calculated d and that actually measured by peripheral quantitative tomography (pQCT; XCT 960, Stratec, Unitrem, Italy) at the same radial site. The D and d values were used to calculate a bending breaking resistance index (BBRI) that is a component of the cross-sectional moment of inertia. The BBRI measured in 5460 women aged 35–89 years, was stable up to the age of 65–70 years and rapidly declined thereafter by 0.7% per year. This profile appears to be due to the fact that the increase in medullary area is compensated in terms of mechanical resistance by enlargement of cross-sectional area. In 68 women with either previous femoral neck (n= 41) or pertrochanteric fracture (n= 27) DXA measurements at proximal and ultradistal radius, lumbar spine and femoral neck were obtained together with the evaluation of proximal radius BBRI. The diagnostic accuracy of BBRI was somewhat comparable to that of spine and femoral neck BMD and significantly superior to that of ultradistal and proximal radius BMD, from which it was derived. Despite the obvious limitation of the cross-sectional nature of this study, our results indicate that a simple re-elaboration of the data obtained by peripheral radial densitometry may achieve diagnostic accuracy for hip fracture risk assessment only marginally lower than that of the direct measure of the BMD of the femoral neck. They also give additional support to the view that bone geometry, particularly for compact skeletal segments, is a determinant of its strength at least as important as bone density. Received: 25 July 2000 / Accepted: 9 April 2001     

The Effects of Pregnancy and Lactation on Bone Mineral Density

We performed a prospective study of bone mineral density (BMD) in 38 women during their first full-term pregnancy until 12 months postpartum. BMD measurements at lumbar spine [L2–L4 (LS)] and forearm [distal 33% (RD) and ultradistal (RUD) region of the radius] were made within 3 months before conception, after delivery, and at 6 and 12 months postpartum. In mid-pregnancy the DXA examination was carried out only at the forearm. Patients were grouped according to duration of lactation as group I, II or III (0–1, 1–6, 6–12 months respectively). During pregnancy there was a significant difference between baseline and delivery (p< 0.001) in the LS, RUD and RD BMD values. In group I there was no statistically significant difference in LS BMD between visits following pregnancy. The RUD BMD loss was recovered by 6 months postpartum (PP6). Group II showed continuous bone loss from delivery until PP6 at LS and RUD. In group III the LS BMD loss continued throughout the lactation period. The RUD BMD dropped (4.9%) until PP6 then increased by 3.0% as measured at 12 months postpartum (PP12). There was no significant change in RD BMD in any of three groups during lactation. At LS bone loss between delivery and PP12 correlated well with the duration of lactation (r=−0.727; p<0.001). We suggest that calcium needed for fetal skeletal growth during pregnancy was gained from maternal trabecular and cortical sites and that calcium needed for infant growth during lactation was drawn mainly from the maternal trabecular skeleton in our patients. The effect of pregnancy and lactation on the maternal bone mass was spontaneously compensated after weaning. Received: 13 July 2000 / Accepted: 19 April 2001     

Bone Mineral Density in French Canadian Women

This cross-sectional study investigated bone mineral density (BMD) at the lumbar spine (L2–4) and femoral neck in French Canadian women residing in the Quebec city area. Data collection was initiated in 1988 and completed in 1994. A total of 747 French Canadian Caucasian women (16–79 years of age) with no metabolic bone disease were evaluated. BMD measurements were obtained using dual-photon absorptiometry (DPA) or dual-energy X-ray absorptiometry (DXA). Anthropometric measures such as weight, height and body mass index (BMI) were recorded. Medical files provided information on demographic characteristics, hormonal profile and lifestyle habits. Results show a curvilinear trend of BMD with aging. Furthermore, the peak BMD at the lumbar spine (L2–4) was reached at 29 years followed by a stable phase until 35 years, after which BMD started to decrease. The pattern of bone evolution at the femoral neck was different, peak BMD being achieved earlier, at 21 years, while after age 26 years a significant decrease was already observed. Women older than 60 years showed the lowest BMD. Regression analysis showed that age, weight and height are determinants of BMD at the lumbar spine and explained 33.9% of inter-individual variation. At the femoral neck, 29.1% of variation was explained by age and height only. In conclusion, our data suggest that French Canadian women have a different pattern of bone loss at the femoral neck compared with the lumbar spine, according to their mean BMD values. Received: 21 July 1997 / Accepted: 15 October 1997     

Influence of Heredity and Environment on Bone Density in Adolescent Boys: A Parent–Offspring Study

The purpose of the present parent–offspring study was to investigate the influence of heredity and environment on bone density in young men. Another aim was to discover whether the same genetic factors influence bone mass, lean mass and muscle strength. Fifty families including a father, mother and one son were investigated. The mothers (aged 44.5 ± 4.4 years) and fathers (aged 47.1 ± 4.4 years) generally had a sedentary lifestyle with little physical activity. As a contrast, all but three of the sons (aged 17.0 ± 0.4 years) were active in ice hockey training. Bone mineral density (BMD, g/cm²) of the total body, head, lumbar spine and femoral neck was measured using dual-energy X-ray absorptiometry. Muscle strength of the hamstrings and quadriceps muscles was also measured in the boys. BMD values of different sites in the fathers, mothers and sons were adjusted for weight, height, age, and any significant influence of environment. Heritability estimates were obtained as regression coefficients with the boys’ adjusted BMD as dependent variable and the adjusted midparent bone density (father BMD + mother BMD/2) as independent variable. Accordingly, heritability explained 34–54% of the variation in the sons’ BMD. Midparent BMD of several sites also predicted the boys’ lean mass and quadriceps strength, and midparent–offspring differences in lean mass predicted midparent–offspring differences in BMD of the total body, head and spine (β= 0.30–0.51, p<0.05). The sons were found to have almost 30% higher femoral neck BMD than their fathers, and physical activity (hours/week) predicted BMD at several sites among the sons β= 0.26–0.34, p <0.05). In conclusion, heritability is a main determinant of the variance in BMD in young men. Based on the results we suggest that the same genetic factors may influence bone mass, lean mass and muscle strength by affecting body size. The present study also emphasizes the importance of physical activity for the development and maintenance of BMD in men. Received: 26 October 1998 / Accepted: 24 February 1999     

Determinants of Bone Mineral Density in Middle Aged Men: A Population-Based Study

Osteoporosis is a growing health problem not only in women but also in men. To assess determinants of bone mineral density (BMD) at the spine and proximal femur, a randomly selected sample of 140 Finnish men aged 54–63 years was measured using fan beam dual-energy X-ray absorptiometry. Isometric muscle strength was measured using a computerized measurement system and cardiorespiratory fitness was assessed with maximal oxygen uptake (VO₂max) using breath-by-breath respiratory gas analyses during an incremental bicycle ergometer exercise. Intakes of calcium and energy were estimated using 4-day food records. Smoking habits and alcohol consumption were assessed from an interview and a 4 week diary, respectively. Isometric muscle strength of triceps and biceps brachii, extensors and flexors of thigh and rectus abdominis correlated significantly with BMD (r= 0.18–0.35, p= 0.02–0.000). Calcium intake correlated positively with femoral (r= 0.19–0.28, p= 0.03–0.003), but not with lumbar BMD. In addition, calcium intake adjusted for dietary energy content (mg/MJ) correlated with femoral BMD (r= 0.25–0.36, p= 0.03–0.000). Smoking had no effect on BMD, whereas alcohol intake correlated positively with BMD at L2–L4 (r = 0.19, p= 0.031). In the multiple linear regression analysis adjusted calcium intake predicted BMD in every site measured, while strength of abdominal muscles predicted BMD at Ward’s triangle and femoral neck. Body weight was a predictor of trochanteric BMD. Body height was the best predictor of lumbar and femoral neck area. We conclude that low dietary calcium intake, weak muscle strength and low body weight are risk factors for low BMD in men. Received: 30 August 1999 / Accepted: 29 December 1999     

Vitamin D Receptor Gene Polymorphisms, Bone Mass, Bone Loss and Prevalence of Vertebral Fracture: Differences in Postmenopausal Women and Men

Bone mineral density (BMD), the major determinant of fracture risk, is under strong genetic control. Although polymorphisms of the vitamin D receptor (VDR) gene have been suggested to account for some of the genetic variation in bone mass, the influence of VDR genotypes on osteoporosis remains controversial. Previous published studies have focused mainly on women, but the pattern of response in men has not been determined. Using the BsmI restriction enzyme, we studied the influence of the different VDR genotypes on bone mass, bone loss and the prevalence of vertebral fractures in a population-based sample of both sexes (n = 326). BMD was measured at the lumbar spine and femoral neck, with a 4-year interval, using dual-energy X-ray absorptiometry. Vertebral fractures were assessed by two lateral radiographs at the beginning and end of the study. The prevalence of the three possible VDR genotypes was similar to those in other Caucasian populations and no differences were found between men and women. Women with the favorable bb genotype showed significantly higher BMD values at the lumbar spine and femoral neck, and a positive rate of BMD change at the femoral neck compared with women with the BB and Bb genotypes. Moreover, women with the bb genotype showed a trend toward a lower prevalence and incidence of vertebral fractures (p= 0.07). We have not found any differences between VDR genotypes in men. In conclusion, VDR gene polymorphisms are related to bone mass and bone loss in women; also a trend in the prevalence of vertebral fractures was observed in postmenopausal women but not in men. Received: 8 June 1998 / Accepted: 7 December 1998