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R D Wasnich

Publications and source records attributed to R D Wasnich.

At least 73 records · Page 4Linked to original sources
PubMed1994

Evidence for both generalized and regional low bone mass among elderly women.

The consistency of bone mass measurements across bone sites was examined in a cohort of elderly Japanese-American women. The study included 744 women of mean age 66.6 years (age range 47-82 years) who had bone densitometry measurements at the spine, calcaneus, and distal and proximal radius. The women were classified at the four bone sites as in the lower, middle, or upper bone mass tertile for their age. Slightly more than half (56%) of the women were in the lower tertile at one or more of the bone sites, and such women were usually in the lower category at more than one site. Of the women, 24% were classified in the lower tertile at all four sites. Furthermore, as a group, women classified as in the low bone mass category at any one site had a low average bone mass at all four sites. Prospectively, the number of low bone mass sites predicted the risk of new spine fractures after adjusting for age and the number of spine and nonspine prevalent fractures. The risk increased approximately 1.3-fold for each additional low bone mass site. A subgroup (15%) of the population had marked heterogeneity in bone mass between sites. These women had one or more lower tertile bone mass site(s) and one or more upper tertile bone mass site(s). The results suggest that osteoporosis may occur as either a generalized or as a regional disorder.

Absorptiometry, Photon↗
PubMed1994

When should bone density measurements be repeated?

We calculated how long to wait before repeating bone mineral density (BMD) measurements to reassess fracture risk. Correlation results from serial measurements of 495 postmenopausal Japanese-American women were used to estimate 95% confidence intervals (CI) for future BMD. After 7 years of follow-up, BMD correlations with the initial measurement ranged between 0.81 and 0.94, depending on age group and measurement site. In this analysis, the period between measurements was defined as the time required for the lower 95% CI to fall below the BMD value corresponding to doubling of fracture risk. Progressive bone loss causes fracture risk to double after 10 years, on average. However, the 95% CIs indicate that a second BMD measurement will detect risk doubling after only 2 or 3 years for some women. For untreated, early postmenopausal women, the period between measurements was approximately 2-5 years for the radius and 4-6 years for the calcaneus, depending on the initial BMD level. The period was approximately 1 year longer for women age 60 and older. Treatments that halve the bone loss rate would increase the period by 1-3 years. In the absence of a second measurement of BMD, the CI will continue to expand with time, corresponding to a wider range in risk between individuals, and a greater proportion of women will be at increased fracture risk. Obtaining a second BMD measurement pinpoints the patient's status within the precision of the measurement. We conclude that repeated BMD measurements will provide a more accurate estimate of fracture risk than a single, baseline measurement.

Age Factors↗
PubMed1994

The peak bone mass of Hawaiian, Filipino, Japanese, and white women living in Hawaii.

Our study compares the bone mass of Hawaiian, Filipino, Japanese, and white women living in Oahu, Hawaii. Eligible women ranged in age from 25 to 34; all had bone mass measurements at the spine, calcaneus, and proximal and distal radius. Their average bone mineral density (BMD) remained stable with age at all four bone sites, indicating that the age range 25-34 may represent the peak bone mass. Bone mass varied, however, between ethnicities; differences in BMD up to 11% were observed. The Hawaiian women had the greatest BMD, and whites had the second greatest BMD at the spine and calcaneus. The Japanese most frequently had the lowest BMD. Differences in body size partly explained the differences; most ethnic differences were reduced or eliminated after adjusting for height and weight. At the spine, the ethnic differences for BMD were also apparent with BMC and with vertebral area. Hawaiian and white women had greater values than Japanese or Filipino women. Differences at the proximal radius resembled the spine, except that whites had the widest proximal widths. The results were more complex for the distal radius. At the distal radius whites had the lowest BMD of the four ethic groups. The difference between whites and Hawaiians derived from the greater bone mineral content (BMC) of the Hawaiian women. By contrast, the difference between whites and the Japanese and Filipinos derived from the wider distal widths of the white women. Compared with the Japanese and Filipino women, the white women appeared to disperse their BMC at the distal radius across a wider bone width.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Racial differences in hip axis lengths might explain racial differences in rates of hip fracture. Study of Osteoporotic Fractures Research Group.

Compared with white women, Asian women have about a 40%-50% and blacks a 50%-60% lower risk of hip fracture, but the reason for this racial difference is not known. Women with a shorter hip axis have a lower risk of hip fracture. To test the hypothesis that a shorter hip axis length could account for the lower risk of hip fracture among Asian and black women, we measured hip axis length in 135 Caucasian, 74 Asian and 50 black women. The mean hip axis lengths of Asian and black women were significantly shorter (1.2 and 0.7 standard deviations, respectively) than that of the whites (p < 0.0001). We estimate that, compared with white women, Asians would have a 47% lower risk (95% confidence interval: 32%-63%) and blacks would have a 32% (15%-45%) lower risk of hip fracture because of their shorter hip axis. We conclude that a shorter hip axis length might be a major factor accounting for Asian women's lower risk of hip fracture and might contribute to the lower risk in black women.

Aged↗
PubMed1994

Spine fracture risk is predicted by non-spine fractures.

A prospective cohort study of 1098 postmenopausal Japanese-American women evaluated the relationship between baseline non-spine fractures and new (incident) spine fractures. At the baseline examination in 1981, prevalent non-spine fractures were ascertained by interview, and prevalent spine fractures by radiograph. Bone mass measurements of the distal radius, proximal radius, calcaneus (1981), the lumbar spine (1984) were obtained and repeated at 1- to 2-year intervals. Women with existing non-spine fractures have a threefold greater risk of subsequent spine fractures, independent of bone mass, and independent of the known association between prevalent spine fractures and subsequent spine fractures. Women with both a prevalent non-spine fracture and low bone mass (50th percentile or lower) have an eightfold greater risk of new spine fractures compared with women above the 50th percentile of bone mass and no prevalent fractures. In addition to low bone mass, both prevalent spine fractures and prevalent non-spine fractures are strong risk factors for subsequent spine fracture. These data suggest that not all osteoporotic risk factors are expressed via bone mass, and that other, unmeasured risk factors, such as bone quality defects, may explain these results. In clinical terms, women with both prevalent fractures and low bone mass should be recognized as being at extremely high risk, and treatment potency should be commensurate with this level of risk.

Adult↗
PubMed1994

Pain and disability associated with new vertebral fractures and other spinal conditions.

Although vertebral fractures are common among older women, little is known about associations with pain and disability. In this prospective study, fractures which occurred after the initial radiograph were strong predictors of back pain and disability at the end of followup, with odds ratios (OR) of approximately 4-5. Other, independently significant predictors were self-reported history of (1) disk disease (OR = 3-9), (2) traumatic back injury (OR = 4-7), and (3) spinal arthritis (OR = 3-6). In longitudinal analyses, new fractures were associated (OR = 6.4; 95% CI = 2.6, 15.6) with increases in back pain frequency (relative to pre-fracture levels). The association with prevalent fractures was weaker, and not significant (OR = 1.7; 95% CI = 0.5, 5.6). The pain frequency index increased approximately 3-fold, relative to pre-fracture levels. At the end of followup (mean = 3.5 years), the index was still two times greater than baseline. We conclude that associations with back pain and disability are greater in magnitude for new vertebral fractures than for prevalent fractures.

Adult↗
PubMed1994

Normal ranges for bone loss rates.

We reported previously that the variability in bone loss rates among postmenopausal women decreases dramatically during the first few years of followup. In this paper, we have examined the distributions of bone loss rates measured at the calcaneus, distal radius and proximal radius. The incidence of physical impairment was five times greater among women with bone loss rates faster than 2 S.D. below the mean. Because the rate of change in bone density was skewed at the lower end of the distribution (representing rapid bone loss), the influence of values at the extreme ends of the distribution were statistically removed in order to estimate the normal distribution of bone loss rates. For the convenience of clinicians, the upper and lower limits of the 90 and 70% normal ranges are presented. Because average bone loss rates vary with age, normal ranges are provided separately by age group. The width of each normal range decreased by at least half after 3 or 4 years of followup, compared to less than 1 year. Consequently, measured loss rates which were well within the normal range at 1 year were sometimes far outside the normal range for longer followup times. We conclude that followup duration has a profound effect on estimates of the normal range, and must be considered when interpreting the clinical significance of measured loss rates.

Adult↗
PubMed1993

A new method for vertebral fracture diagnosis.

A number of methods have been proposed for estimating the prevalence of vertebral fractures. Most methods are based on the distribution of normal vertebral dimensions in the population. However, these methods fail to identify a significant proportion (20-30% or more) of fractures documented on serial radiographs. This may occur because vertebral size varies between individuals as a result of differences in body size (and possibly other factors), and a normal range based on population reference data may be too large. In this paper, a new method is described for identifying vertebral fractures that are missed using diagnostic criteria based on vertebral dimension distributions of the population. This new method is based on calculating the average vertebral size, and statistical confidence limits, for the individual. The average vertebral size method was evaluated by testing its ability to identify incident fractures (which were identified from changes in dimensions compared to previous radiographs), using only the final film. The new method correctly identified most (81% of crush and 83% of wedge) incident fractures on the final radiograph. In contrast, criteria based on population distributions correctly identified only 53% of crush and 72% of wedge incident fractures. Using prospective data, prevalent fractures identified using both population-based and individual size-based criteria predicted the risk of incident fractures. Furthermore, incident fractures identified using both methods (population- and individual-based criteria) were associated with increased back pain. These data suggest that both types of prevalent deformities are important indicators of disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Predicting vertebral fracture incidence from prevalent fractures and bone density among non-black, osteoporotic women.

We evaluated the ability of bone density and vertebral fractures at baseline to predict vertebral fracture incidence in a cohort of postmenopausal women with osteoporosis. The study population was 380 postmenopausal women (mean age 65 years) treated for osteoporosis in a randomized, placebo-controlled, clinical trial of the bisphosphonate etidronate at seven geographic centers in the United States. Baseline measurements of bone mineral density were obtained in 1986 by quantitative computed tomography at the spine and dual-photon absorptiometry at the lumbar spine and hip. Vertebral fractures were documented on serial spine radiographs. Proportional hazards models were used to evaluate the ability to predict the risk of subsequent fractures during an average of 2.9 years of follow-up. Presence of one or two fractures increased the rate of new vertebral fractures 7.4-fold (95% confidence interval = 1.0 to 55.9). Additional fractures at baseline further increased the fracture rate. A decrease of 2 standard deviations in spinal bone density by absorptiometry was associated with a 5.8-fold increase in fracture rate (95% confidence interval = 2.9 to 11.6). The lowest and highest quintiles of bone density had absolute fracture rates of 120 and 6 cases per 1000 patient-years, respectively. In general, the simultaneous use of two predictors (bone density and prevalent fractures or two bone density measurements) improved fracture prediction, compared with the use of a single predictor. We conclude that both bone density and prevalent vertebral fractures are strong, complementary predictors of vertebral fracture risk. The results suggest that physicians can use bone density and prevalent vertebral fractures, individually or in combination, as risk factors to identify patients at greatest risk of new fractures.

Aged↗
PubMed1993

Bone mass and beyond: risk factors for fractures.

Numerous prospective studies have demonstrated a strong relationship between bone mass and fracture risk. The fact that the bone mass distributions of fracture and nonfracture cases overlap does not necessarily indicate a shortcoming of bone mass, but might instead be due to the sporadic nature of falls and the influence of other fracture risk factors. The recent finding that prevalent fractures are strong predictors of fracture risk, independent of bone mass, suggests (but does not prove) that there may be other, potentially measurable fracture risk factors that complement, and act independently of, bone mass. This paper reviews possible mechanisms by which prevalent fractures might serve as etiologic risk factors, or as surrogate indicators of other risk factors. Potential risk factors other than bone mass and prevalent fractures are also considered. Whether or not etiologic fracture risk factors other than bone mass can be identified, it appears that treatments that influence bone will be most effective if begun early, before bone strength becomes impaired and fractures begin to occur.

Absorptiometry, Photon↗
PubMed1993

Four-year study of intermittent cyclic etidronate treatment of postmenopausal osteoporosis: three years of blinded therapy followed by one year of open therapy.

PURPOSE: To determine the effect of long-term intermittent cyclic etidronate treatment on spinal bone density and vertebral fracture rates. PATIENTS AND METHODS: Postmenopausal osteoporotic women (n = 423) were randomized initially into a 2-year, double-blind, multicenter study; it was extended to a third year of blinded treatment followed by open-label treatment: 357 patients continued treatment in Year 3 (305 receiving blinded therapy and 52 receiving calcium supplementation) and 277 in Year 4. During Years 1 through 3, patients received double-blind treatment with phosphate (1.0 g) or placebo twice daily for 3 days, etidronate (400 mg) or placebo daily for 14 days, and calcium (500 mg) daily for the remainder of each 91-day treatment cycle. During Year 4, open-label intermittent cyclic etidronate therapy (without preceding phosphate) was administered to all patients. Spinal bone density and vertebral fracture rates were the main outcome measures. RESULTS: During Year 3, etidronate therapy maintained the significant increases in spinal bone mineral density of the first 2 years. Over the 3-year period, proximal femur bone density increased in etidronate-treated patients. Etidronate therapy for 3 years significantly decreased the vertebral fracture rate in patients at higher risk for fracture (low spinal bone density and three or more vertebral fractures at study entry), as compared with nonetidronate treatment (228 versus 412 fractures per 1,000 patient-years, respectively; p < 0.05). After 1 year of open-label treatment, patients previously treated with etidronate maintained bone mass, and vertebral fracture rates in all groups were lower than in any other study period. There were no apparent serious adverse effects. CONCLUSIONS: Three years of intermittent cyclic etidronate therapy produced significant increases in spinal and hip bone density, with a significant reduction in vertebral fracture rates in patients at higher fracture risk. Maintenance of bone mass and low fracture rate were observed when etidronate was continued for an additional year.

Analysis of Variance↗
PubMed1993

Declining bone loss rate variability with increasing follow-up time.

Bone loss rates are believed to vary substantially among post-menopausal women. The belief, however, might be largely based upon comparisons of loss rates measured with considerable error. This issue arises because the precision of the bone mass instrumentation (1-2% errors in measuring bone mass) is similar in magnitude to the loss rate (typically 1-2% of bone mass per year). The 'true' variability in loss rates, however, can be estimated by adjusting for instrument errors. An equation is presented which estimates the true variability in loss rates from a study sample. The adjustment was examined using a cohort of post-menopausal, Japanese-American women living in Hawaii. The study examined the calcaneus, distal, and proximal radius sites. The results suggest that measurement errors did not markedly inflate the bone loss variability. Even after adjustment for measurement errors considerable variability in loss rates remained. The variability was examined for various follow-up durations. Both the observed and adjusted loss rates had smaller standard deviations over long intervals than over short intervals. This result suggests that the more extreme rates of change in bone mass over a year or two were often not sustained. The implications of this finding for sample size calculations in longitudinal studies are examined. The results also indicate that the length of follow-up and instrument precision should be taken into consideration when comparing the proportion of fast losers between populations.

Absorptiometry, Photon↗
PubMed1992

Relationship between bone mass and rates of bone change at appendicular measurement sites.

The rate of bone change among postmenopausal women may vary depending upon the initial bone mass. Examining this possibility is difficult, however, because of a negative statistical bias that occurs when change is regressed against the initial value of the same variable. In this article, four statistical methods were applied to measure the association between bone mass and the rate of bone change. The study population was Japanese-American women, who were monitored for approximately 5 years. Bone changes were determined for the calcaneus and the distal and proximal radius. The results were consistent across the bone sites but differed between statistical methods. Three of the four methods indicated that the women with the greater bone mass had the greater loss rates. The fourth method did not support this association. Possible reasons for the discordant results are discussed. Using the "best" estimate of the relationship, a gradual convergence of bone mass was projected over time toward the population mean. The convergence occurred because women with higher bone mass had a somewhat faster loss rate than women with lower bone mass. Overall, however, the variation in bone mass between individuals was large compared to the rate of convergence.

Absorptiometry, Photon↗
PubMed1992

Ability of vertebral dimensions from a single radiograph to identify fractures.

It has been proposed that vertebral dimensions be used to objectively identify vertebral fractures, permitting standardization of methodology for comparisons between studies. In this report, we evaluate the ability of various vertebral dimensions and ratios to identify "abnormal" vertebrae. As no "gold standard" exists for prevalent vertebral fractures, we examined the ability of cross-sectional dimensions (at a single point in time) to detect fractured vertebrae that had been identified from changes in dimensions compared with previous radiographs. Theoretically, a cutoff of 3 SD below the mean will rarely misclassify normal vertebrae as fractured (specificity = 99.9%). However, we found that this cutoff correctly identified only about 70% of the incident fractures. A less stringent criterion (2 SD below the mean; theoretical specificity = 97.7%) identified about 85-90% of true fractures. Dividing by stature or other vertebral heights sometimes yielded marginal improvements in the ability of the anterior or posterior height dimensions to diagnose fractures. The results suggest that the true fracture prevalence may sometimes be substantially higher than suggested by cross-sectional vertebral measurements.

Bone and Bones↗
PubMed1992

A method for estimating the uncertainty of future bone mass.

The development of statistical models for estimating fracture probability is a promising method for quantitating and optimizing the clinical utility of bone mass measurements. Earlier models have assumed that future bone mass could be predicted exactly and were, therefore, limited to analyses that assume the loss rate is known in advance. Since bone loss rates may vary over time and cannot be predicted accurately, we have developed a new model, based on empirical data, that estimates the degree of uncertainty associated with predicted bone mass. Without a bone mass measurement, the population mean must be assumed for an individual. For the calcaneus, the standard deviation of the population distribution is about 60 mg/cm2. By measuring bone mass, one can determine how close or far from the mean an individual's true bone mass is, with a standard deviation (SD) of about 3 mg/cm2. Without a subsequent bone mass measurement, our model predicts that the uncertainty (standard deviation) in calcaneal bone mass will increase approximately sixfold (relative to the reproducibility at the initial measurement) over a period of five years for women under age 60, from 3 mg/cm2 to 19 mg/cm2. The five-year increase in uncertainty is approximately fourfold for women over age 60, from 3 to 13 mg/cm2. However, the uncertainty in bone mass for an individual five years after the initial measurement is still only one third to one fifth that of the entire population, and can be reduced to the initial level by obtaining another measurement. Furthermore, the predicted (or measured) values are usually much better estimates of an individual's true bone mass than simply assuming the population average.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1991

Pre-existing fractures and bone mass predict vertebral fracture incidence in women.

OBJECTIVE: To determine the independent contributions of bone mass and existing fractures as predictors of the risk for new vertebral fractures. SUBJECTS: Postmenopausal Japanese-American women. MEASUREMENTS: Baseline measurements of the distal radius, the proximal radius, and the calcaneus were obtained in 1981 using single-photon absorptiometry. Measurements of the lumbar spine were obtained in 1984 using dual-photon absorptiometry. Prevalent vertebral fractures were identified using dimensions measured on lateral radiographs; vertebral height values more than 3 SD below vertebra-specific means were considered to indicate fracture. Statistical models were used to evaluate the utility of bone mass and existing (prevalent) fractures to predict the risk for new fractures during an average follow-up of 4.7 years. MAIN RESULTS: Differences of 2 SD in bone mass were associated with fourfold to sixfold increases in the risk for new vertebral fractures. A single fracture at the baseline examination increased the risk for new vertebral fractures fivefold. Presence of two or more fractures at baseline increased the risk 12-fold. A combination of low bone mass (below the 33d percentile) and the presence of two or more prevalent fractures increased the risk 75-fold, relative to women with the highest bone mass (above the 67th percentile) and no prevalent fractures. Stature, body mass index, arm span, and spinal conditions such as scoliosis, osteoarthritis, and sacroiliitis did not predict fracture incidence (P greater than 0.05). Weight was marginally predictive (P = 0.04) of fracture incidence but became nonpredictive after adjusting for bone mass (P greater than or equal to 0.05). CONCLUSIONS: Both bone mass and prevalent vertebral fractures are powerful predictors of the risk for new vertebral fractures. Combining information about bone mass and prevalent fracture appears to be better for predicting new fractures than either variable alone. Physicians can use these risk factors to identify patients at greatest risk for new fractures.

Absorptiometry, Photon↗