Bone Mineral Density and Vertebral Fractures in Men

In women, many studies indicate that the risk of vertebral fragility fractures increases as bone mineral density (BMD) declines. In contrast, few studies are available for BMD and vertebral fractures in men. It is uncertain that the strength of the relationship between BMD and fractures is similar in magnitude in middle-aged men and in postmenopausal women. In the present study, 200 men (mean age 54.7 years) with lumbar osteopenia (T-score <−1.5) were recruited to examine the relationships between spine BMD and hip BMD and the associations of BMD with vertebral fractures. Lumbar BMD was assessed from L2 to L4, in the anteroposterior view, using dual-energy X-ray densitometry. At the upper left femur, hip BMD was measured at five regions of interest: femoral neck, trochanter, intertrochanter, Ward’s triangle and total hip. Spinal radiographs were analyzed independently by two trained investigators and vertebral fracture was defined as a reduction of at least 20% in the anterior, middle or posterior vertebral height. Spinal radiographs evidenced at least one vertebral crush fracture in 119 patients (59.5%). The results of logistic regression showed that age, femoral and spine BMDs were significant predictors of the presence of a vertebral fracture. Odds ratios for a decrease of 1 standard deviation ranged from 1.8 (1.3–2.8) for spine BMD to 2.3 (1.5–3.6) for total hip BMD. For multiple fractures odds ratios ranged from 1.7 (1.1–2.5) for spine BMD to 2.6 (1.7–4.3) for total hip BMD. In all models, odds ratios were higher for hip BMD than for spine BMD, particularly in younger men, under 50 years. A T-score <−2.5 in the femur (total femoral site) was associated with a 2.7-fold increase in the risk of vertebral fracture while a T-score <−2.5 in the spine was associated with only a 2-fold increase in risk. This study confirms the strong association of age and BMD with vertebral fractures in middle-aged men, shows that the femoral area is the best site of BMD measurement and suggests that a low femoral BMD could be considered as an index of severity in young men with lumbar osteopenia. Received: 27 October 1998 / Accepted: 22 February 1999     

Long-Term Risk of Osteoporotic Fracture in Malmö

The objectives of the present study were to estimate long-term risks of osteoporotic fractures. The incidence of hip, distal forearm, proximal humerus and vertebral fracture were obtained from patient records in Malmo¨, Sweden. Vertebral fractures were confined to those coming to clinical attention, either as an inpatient or an outpatient case. Patient records were examined to exclude individuals with prior fractures at the same site. Future mortality rates were computed for each year of age from Poisson models using the Swedish Patient Register and the Statistical Year Book. The incidence and lifetime risk of any fracture were determined from the proportion of individuals fracture-free from the age of 45 years. Lifetime risk of shoulder, forearm, hip and spine fracture were 13.3%, 21.5%, 23.3% and 15.4% respectively in women at the age of 45 years. Corresponding values for men at the age of 45 years were 4.4%, 5.2%, 11.2% and 8.6%. The risk of any of these fractures was 47.3% and 23.8% in women and men respectively. Remaining lifetime risk was stable with age for hip fracture, but decreased by 20–30% by the age of 70 years in the case of other fractures. Ten and 15 year risks for all types of fractures increased with age until the age of 80 years, when they approached lifetime risks because of the competing probabilities of fracture and death. We conclude that fractures of the hip and spine carry higher risks than fractures at other sites, and that lifetime risks of fracture of the hip in particular have been underestimated. Received: 9 November 1999 / Accepted: 2 February 2000     

An Assessment Tool for Predicting Fracture Risk in Postmenopausal Women

Due to the magnitude of the morbidity and mortality associated with untreated osteoporosis, it is essential that high-risk individuals be identified so that they can receive appropriate evaluation and treatment. The objective of this investigation was to develop a simple clinical assessment tool based on a small number of risk factors that could be used by women or their clinicians to assess their risk of fractures. Using data from the Study of Osteoporotic Fractures (SOF), a total of 7782 women age 65 years and older with bone mineral density (BMD) measurements and baseline risk factors were included in the analysis. A model with and without BMD T-scores was developed by identifying variables that could be easily assessed in either clinical practice or by self-administration. The assessment tool, called the FRACTURE Index, is comprised of a set of seven variables that include age, BMD T-score, fracture after age 50 years, maternal hip fracture after age 50, weight less than or equal to 125 pounds (57 kg), smoking status, and use of arms to stand up from a chair. The FRACTURE Index was shown to be predictive of hip fracture, as well as vertebral and nonvertebral fractures. In addition, this index was validated using the EPIDOS fracture study. The FRACTURE Index can be used either with or without BMD testing by older postmenopausal women or their clinicians to assess the 5-year risk of hip and other osteoporotic fractures, and could be useful in helping to determine the need for further evaluation and treatment of these women. Received: 7 November 2000 / Accepted: 23 May 2001     

Site-Specific Variation in the Classification of Osteoporosis, and the Diagnostic Reclassification Using the Lowest Individual Lumbar Vertebra T-score Compared with the L1–L4 Mean, in Early Postmenopausal Women

In this study we report first the concordance and variation in diagnostic osteoporosis classification using multiple skeletal site measurements compared with the lumbar spine only; and secondly, at the lumbar spine, the variation and diagnostic osteoporosis reclassification using the lowest individual vertebra T-score compared with the L1–L4 mean T-score. One hundred and fifty early postmenopausal women were evaluated as part of the recruitment for a multicenter osteoporosis prevention study. Bone mineral density (BMD) was restricted such that no more than 10% of the subjects had a lumbar spine BMD below 0.8 g/cm². Forty-seven per cent of the subjects were classified as having low bone mass (T-score ≤−1.0) at the lumbar spine, 63% at the mid-forearm, 39% at the distal forearm and 50% at the hip (p<0.05). The greatest proportion of subjects were categorized as osteoporotic at the lumbar spine, followed by the forearm and then the hip. Correlation between sites ranged from 0.57 to 0.60 (p<0.01). Eighty-one percent of the subjects had a significant difference between their highest and lowest individual lumbar vertebra T-score (defined as a difference outside the 90% confidence interval coefficient of variation T-score value). Using the lowest individual lumbar T-score, recategorized 33% of the subjects classified as osteopenic (based on the mean L1–L4 T-score) as osteoporotic, and 23% of those classified as normal as osteopenic (p<0.05). Of all four vertebrae, L2 had the highest T-score in 37.7% of the subjects (mean −0.3) and L4 the lowest in 61% (mean −1.5) (mean difference 1.2 units, 95% CI 0.7 to 1.7). The classification of osteoporosis varies according to skeletal site, with pronounced differences in the early menopausal population. T-scores are useful for characterizing subjects with the highest risk of osteoporosis but BMD and fracture risk must be recognized in a continuum. Individual T-scores of the lumbar vertebrae show wide variation in the absence of degenerative spinal disease or vertebral collapse and the use of the lowest, significantly different, individual lumbar vertebra T-score reclassified over half of the subjects in this study. This poses a great therapeutic dilemma in clinical practice, particularly if these fractures are at higher risk of future collapse. Received: 9 November 1999 / Accepted: 27 April 2000     

Can the WHO Criteria for Diagnosing Osteoporosis be Applied to Calcaneal Quantitative Ultrasound?

With the increasing number of quantitative ultrasound (QUS) devices in use worldwide it is important to develop strategies for the clinical use of QUS. The aims of this study were to examine the age-dependence of T-scores and the prevalence of osteoporosis using the World Health Organization Study Group criteria for diagnosing osteoporosis and to examine the T-score threshold that would be appropriate to identify women at risk of osteoporosis using QUS. Two groups of women were studied: (i) 420 healthy women aged 20–79 years with no known risk factors associated with osteoporosis; (ii) 97 postmenopausal women with vertebral fractures. All subjects had dual-energy X-ray absorptiometry (DXA) measurements of the spine and hip and QUS measurements on three calcaneal ultrasound devices (Hologic Sahara, Hologic UBA575+, Osteometer DTUone). A subgroup of 102 (76 on the DTUone) healthy women aged 20–40 years was used to estimate the young adult mean and SD for each QUS and DXA measurement parameter to calculate T-scores. The age-related decline in T-scores for QUS measurement parameters was half the rate observed for the bone mineral density (BMD) measurements. The average T-score for a woman aged 65 years was –1.2 for QUS measurements and –1.75 for the BMD measurements. When osteoporosis was defined by a T-score ≤–2.5 the prevalence of osteoporosis in healthy postmenopausal women was 17%, 16% and 12% for lumbar spine, femoral neck and total hip BMD respectively. When the same definition was used for QUS measurements the prevalence of osteoporosis ranged from 2% to 8% depending on which ultrasound device and measurement parameter was used. Four different approaches, based on DXA-equivalent prevalence rates of osteoporosis, were utilized to examine which T-score threshold would be appropriate for identifying postmenopausal women at risk of osteoporosis using QUS measurements. These ranged from –1.05 to –2.12 depending upon the approach used to estimate the threshold and on which QUS device the measurements were performed, but all were significantly lower than the threshold of –2.5 used for BMD measurements. In conclusion, the WHO threshold of T=–2.5 for diagnosing osteoporosis requires modification when using QUS to assess skeletal status. For the three QUS devices used in this study, a T-score threshold of –1.80 would result in the same percentage of postmenopausal women classified as osteoporotic as the WHO threshold for BMD measurements. Corresponding T-score thresholds for individual measurement parameters on the two commercially available devices were –1.61, –1.94 and –1.90 for Sahara BUA, SOS and estimated heel BMD respectively and –1.45 and –2.10 for DTU BUA and SOS respectively Additional studies are needed to determine suitable T-score thresholds for other commercial QUS devices. Received: 25 June 1999 / Accepted: 29 September 1999     

Contact Quantitative Ultrasound: An Evaluation of Precision, Fracture Discrimination, Age-Related Bone Loss and Applicability of the WHO Criteria

The aim of this study was to assess a dry calcaneal quantitative ultrasound (QUS) device by examining: (i) short- and long-term precision; (ii) the ability of the ultrasound parameters to identify women with vertebral fractures; (iii) age- and menopause-related bone loss; (iv) applicability of the WHO criteria in scan interpretation. The study group consisted of 422 healthy women with no risk factors associated with osteoporosis (227 premenopausal and 195 postmenopausal) and 93 women with one or more vertebral fractures. All women had calcaneal QUS and bone mineral density (BMD) measurements of the lumbar spine and hip performed. Broadband ultrasound attenuation (BUA) and speed of sound (SOS) measurements in the heel were combined and expressed as estimated heel BMD. Short-term precision studies yielded coefficient of variations of 0.3% for SOS, 4% for BUA and 3.3% for estimated heel BMD. Standardized short-term precision values were approximately 0.2 SD. Long-term standardized precision errors ranged from 0.17 to 0.38 SD. All the QUS and BMD measurement parameters showed significant negative relationships with age in the postmenopausal group. Annual losses were 0.35 dB/MHz per year for BUA, 0.56 m/s per year for SOS and 0.002 g/cm² per year for estimated heel BMD. All the QUS and BMD parameters were able to discriminate between healthy postmenopausal women and women with vertebral fracture. Age-adjusted odds ratios for each SD decline in QUS measurements were 3.63, 5.25 and 4.79 for BUA, SOS and estimated heel BMD respectively. Corresponding odds ratios for BMD at the lumbar spine, femoral neck and total hip were 2.39, 2.51 and 2.95 respectively. When the QUS and BMD parameters were expressed as T-scores, estimated heel BMD showed the least age-related decline, while femoral neck BMD displayed the greatest decrease with age. The mean T-score and prevalence of osteoporosis (T<−2.5) for a Caucasian woman aged 60–65 years were −1.35 and 21% respectively for the lumbar spine compared with −0.59 and 2% for estimated heel BMD. In conclusion, this study revealed that contact ultrasound can detect age- and menopause-related influences on bone status and was able to discriminate between healthy individuals and women with vertebral fracture. However, the widely accepted threshold of a T-score of less than −2.5 for the definition of osteoporosis may need modifying for the interpretation of QUS scans. Received: 8 February 1999 / Accepted: 5 May 1999     

Use of Clinical Risk Factors in Elderly Women with Low Bone Mineral Density to Identify Women at Higher Risk of Hip Fracture: The EPIDOS Prospective Study

Elderly women with very low bone mineral density (BMD) (T-score ≤−3.5) have a risk of hip fracture more than two times higher than the average risk of women of the same age. Using data from the EPIDOS prospective study, we have shown that by measuring BMD on the 50% of women who have the lowest weight, it is possible to identify the majority of these women at higher risk. In the present analysis, we assessed whether the use of clinical risk factors, in the subset of women selected for osteodensitometry and with moderately low BMD (T-score between −3.5 and −2.5), allows the identification of another subgroup of women with a risk 2 times higher than average and, thereby, increases the efficiency of selective BMD screening. We then assessed the discriminant value for hip fracture of the overall screening strategy (i.e., use of weight to select women for osteodensitometry, then use of clinical risk factors to enhance the predictive value of BMD), and compared it with the value of BMD used as a population screening tool. In total, 6933 EPIDOS participants, aged 75 years or above, were included in this analysis. Using Cox regression models, we first determined which baseline factors were most predictive of hip fracture among the 1588 women with weight below median (selection criteria for osteodensitometry in the proposed strategy) and T-score between −3.5 and −2.5. Based on the relative risk (RR) estimates from the final risk function, we calculated an individual risk score for hip fracture. We assessed the incidence of hip fracture for each value of the score, and determined the cutoff to identify women with a risk about 2 times higher than the average risk in this elderly cohort. The overall screening strategy (i.e., selective BMD measurement based on weight, followed by clinical fracture risk assessment) identifies two subgroups of higher risk women: a group with very low BMD (T-score ≤–3.5), and another group with moderately low BMD (T-score between –3.5 and –2.5) but a high fracture risk score. We calculated the total number of women classified as being at high risk, and assessed the overall sensitivity and specificity of this strategy to identify elderly women who will suffer a hip fracture. Among women with weight below median and T-score between −3.5 and −2.5, the factors most predictive of the risk of hip fracture were age, history of fall, ability to do the tandem walk (test of dynamic balance), gait speed and visual acuity. A simple additive score based on these factors (except visual acuity) allows a high-risk group (risk about 2 times higher than average) to be clearly distinguished from a low-risk group (risk below average). Overall, the proposed strategy identifies approximately 15% of the women in the cohort as being at high risk, i.e., 543 women with T-score ≤−3.5 and 503 women with −3.5 <T-score ≤−2.5 and a high fracture risk score. The sensitivity for hip fracture is equal to 37% and the specificity to 85%, which is equivalent to the discriminant value of BMD as a population screening tool. In elderly women, the use of a simple clinical risk score, in women with previous BMD values, allows the number of high-risk women identified to be increased. Overall, the proposed screening strategy (use of weight to select women for osteodensitometry, and then use of clinical risk factors to enhance the predictive value of BMD) has the same discriminant value for hip fracture as BMD used as a population screening tool. Received: 20 November 2001 / Accepted: 11 February 2002     

Do Men and Women Fracture Bones at Similar Bone Densities?

When the World Health Organization (WHO) guidelines for the definition of osteoporosis in postmenopausal women were identified similar proposals were not developed for men as there was insufficient evidence about the relationship between bone density and fracture in men. We have therefore examined the relationship between bone density and vertebral fracture in men and women attending for assessment of possible osteoporosis. Two hundred and sixty-four women (age 64 [SD 10] years) and 37 men (age 55 [10] years) were studied. Bone density was measured in the lumbar spine and femoral neck by dual-energy X-ray absorptiometry and expressed both as bone mineral density (BMD; g/cm²) and as T-scores. In both sexes there was a sigmoid relationship between the cumulative frequency of vertebral fracture and bone density at both sites. There was a linear relationship between the log odds of fracture and bone mass for both sexes and both sites (r= 0.97–0.99; p<0.0001). The slope of these lines was significantly steeper for men than women. The BMD at which there was 50% risk of fracture was higher in men than women (0.908 vs 0.844 g/cm²). The difference between the slopes was similar when the bone mass was expressed as a T-score. However, the T-score associated with 50% prevalence of fracture was similar in the two sexes (F: −2.77 vs M: −2.60). We conclude that although there is a different relationship between bone density and fracture in the two sexes the current WHO definition of osteoporosis in postmenopausal women can be appropriately applied to men. Received: 24 February 1999 / Accepted: 12 July 1999     

The Burden of Osteoporotic Fractures: A Method for Setting Intervention Thresholds

The aim of this study was to assess the relationship between morbidity from hip fracture and that from other osteoporotic fractures by age and sex based on the population of Sweden. Osteoporotic fractures were designated as those associated with low bone mineral density (BMD) and those that increased in incidence with age after the age of 50 years. Severity of fractures was weighted according to their morbidity using utility values based on those derived by the National Osteoporosis Foundation. Morbidity from fractures other than hip fracture was converted to hip fracture equivalents according to their disutility weights. Excess morbidity was 3.34 and 4.75 in men and women at the age of 50 years, i.e. the morbidity associated with osteoporotic fractures was 3–5 times that accounted for by hip fracture. Excess moribidity decreased with age to approximately 1.25 between the ages of 85 and 89 years. On the assumption that the age- and sex-specific pattern of fractures due to osteoporosis is similar in different communities, the computation of excess morbidity can be utilized to determine the total morbidity from osteoporotic fractures from knowledge of hip fracture rates alone. Such data can be used to weight probabilities of hip fracture in different countries in order to take into account the morbidity from fractures other than hip fracture, and to modify intervention thresholds based on hip fracture risk alone. If, for example, a 10-year probability of hip fracture of 10% was considered an intervention threshold, this would be exceeded in women with osteoporosis aged 65 years and more, but when weighted for other osteoporotic fractures would be exceeded in all women (and men) with osteoporosis. Received: 1 May 2000 / Accepted: 1 December 2000     

Inappropriate Reference Range for Peak Bone Mineral Density in Dual-energy X-ray Absorptiometry: Implications for the Interpretation of T-scores

An inappropriate reference range for peak bone mineral density (BMD) may result in identification of an incorrect proportion of subjects with osteopenia and osteoporosis at dual-energy X-ray absorptiometry (DXA). In this study, we assessed the prevalence of low BMD in Turkish young adults with respect to local population reference range T-scores and the US reference range T-scores. The BMD values of lumbar spine (L1–L4) and proximal femur (femoral neck, intertrochanter, trochanter, Ward”s triangle and total) were measured by DXA in 323 healthy young adults (171 women, 152 men) aged 19–25 years. The World Health Organization criteria for the diagnosis of osteopenia (−2.5 <T-score <−1) and osteoporosis (T-score ≤−2.5) were applied. In women, the means of the US reference range T-scores were significantly lower than zero at the spine and proximal femoral sites (p<0.0001). In men, the means of the US reference range T-scores were significantly lower than zero at the spine, femoral neck, intertrochanter, total femur (p<0.0001) and trochanter (p<0.05), but not at Ward”s triangle (p=0.92). When the diagnoses were based on local population reference range T-scores instead of the US reference range T-scores, the prevalence of low BMD (T-score <−1) in women fell from 50.3% to 14.0% at the lumbar spine and from 60.8% to 14.6% at the femoral neck, and in men from 42.8% to 15.8% at the lumbar spine and from 30.9% to 17.1% at the femoral neck. Our data suggest that individual populations should use their own reference range T-scores to avoid misdiagnoses of osteopenia and osteoporosis by DXA. Received: 4 November 1999 / Accepted: 29 March 2000