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R D Wasnich

Publications and source records attributed to R D Wasnich.

At least 19 recordsLinked to original sources
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↗
PubMed1991

A comparison of hip fracture incidence among native Japanese, Japanese Americans, and American Caucasians.

Hip fracture incidence rates among men and women of Japanese ancestry living on Oahu, Hawaii, from 1979 to 1981 were compared with rates for Japanese living on Okinawa, Japan, from 1984 to 1985. Both rates were further compared with those for various American Caucasian populations, including that of Rochester, Minnesota, from 1978 to 1982. Age-specific and cumulative (age 50-84 years) hip fracture rates among persons of Japanese ancestry were approximately half that of Caucasians for both sexes. Although diet and other cultural attributes of the Oahu group have become more westernized than the Okinawan population, there were no detectable differences in hip fracture rates between Oahu and Okinawa Japanese. Additional studies are needed to determine whether the observed differences in fracture rates between Caucasians and Japanese might be related to differences in bone mass, body size, frequency of falls, or other factors.

Adult↗
PubMed1991

Evaluation of adverse health outcomes associated with vertebral fractures.

Little is known about the frequency or degree to which vertebral fractures cause pain and physical disability. The purpose of this investigation was to examine the advantages of risk analysis over other statistical techniques (e.g., correlation analysis) for quantifying relationships between vertebral fractures and outcomes such as pain and disability. Subjects who volunteered to participate in studies of osteoporosis were asked about pain and disability. The number and degree of vertebral deformities were assessed from radiographs. Strong associations were observed between the most severe vertebral deformities and the risk of high pain or disability scores, while weaker associations were observed for moderate deformities. There did not appear to be any association between vertebral deformity and risk of moderate levels of pain or disability. Because of the potential for bias in cross-sectional studies such as this, the magnitude of these findings must be considered tentative. We conclude that risk analysis is an appropriate method for quantifying the relationship of vertebral fractures with pain and disability, but that prospective studies are now needed.

Back Pain↗
PubMed1991

Long-term precision of bone loss rate measurements among postmenopausal women.

Repeated measurements of bone mineral content can indicate the rate of bone loss among postmenopausal women. The clinical utility of such loss rate measurements will depend upon the long-term precision of the measurements. We have analyzed the precision of appendicular bone measurements among 495 Japanese-Americans followed for an average of 5.3 years and of both appendicular and axial measurements among 70 clinical trial participants followed for 2 years. Tables were derived from these analyses to quantitate the precision of individual loss rates under varying measurement conditions that might be encountered in clinical practice. The results demonstrate that only unusually rapid loss rates could be identified with confidence within short intervals, such as 1 year or 2. Extending the length of follow-up, however, appreciably improved the measured loss rate precision. In comparisons between bone sites, appendicular sites were determined to achieve a specified precision within the shortest intervals, followed by spine dual photon absorptiometry measurements. Spine quantitative computerized tomography measurements and measurements of hip sites required considerably longer follow-up intervals to achieve comparable precision.

Aged↗
PubMed1991

The clinical application of serial bone mass measurements.

Although the short-term precision of various bone mineral content (BMC) measurements is known, questions about the clinical use of serial BMC measurements remain: how frequently should BMC be measured? When is it appropriate to calculate bone loss rates? How are estimates of loss rate interpreted? This paper discusses both biological and technical sources of uncertainty, and the estimation of confidence limits for measured bone loss rates. For many, possibly most, patients, calculation of bone loss rate may not be necessary; however, repeated measures of BMC can still be useful for re-evaluating fracture risk. Indications for repeating BMC measurements may include low initial BMC (moderate to high fracture risk), anticipation of rapid bone loss (e.g., menopause, estrogen discontinuation), and verification of treatment efficacy.

Bone Density↗
PubMed1991

Age-related changes in bone mass among Japanese-American men.

Bone mass and appendicular bone loss rates were examined in a cohort of Japanese-American men. Across their age range (ages 61 to 82 years) bone mass steadily declined at the proximal and distal radius, and at the calcaneus. The cross-sectional reduction in bone mass was 3.5-6.3% per decade at the various sites. Longitudinal measurements of the same cohort indicated greater losses than suggested by the cross-sectional data, yet still less than 10% per decade. Linear trends of increasing loss rates with aging were significant at the calcaneus, and marginally significant at the radius sites. However, the oldest men in the cohort strongly influenced these trends. Men under age 75 had essentially constant annual rates of bone loss. The most elderly men had both the lowest bone mass and the greatest bone loss rates.

Age Factors↗
PubMed1991

Characteristics of respondents and nonrespondents in a prospective study of osteoporosis.

During 1981-1982, a cohort of elderly Japanese Americans living in Hawaii was recruited for an epidemiologic study of osteoporosis. The male subjects were simultaneously being examined for an epidemiologic study of heart disease. Baseline data collected from both the men and women at a previous heart disease examination were used to compare responders vs nonresponders. The target population for the osteoporosis study consisted of 1685 men and 1594 women. Of these, 1379 men (81.8%) and 1105 women (72.0%) participated in the initial osteoporosis examination. For each sex, nonrespondents were older and had higher systolic blood pressure levels than did the respondents. Male nonresponders had a higher stroke prevalence and more frequent recent use of vasodilator medicine. Female nonresponders had a less frequent history of having ever taken female hormones than did the responders. The responders and nonresponders were reasonably similar in other respects, as indicated by the comparison of more than 40 other variables. This suggests that nonresponse bias is probably not a major influence in exposure-disease associations in this osteoporosis cohort. We believe this is the first published report dealing with nonresponse characteristics in a cohort study of osteoporosis.

Aged↗
PubMed1991

Vertebral dimension differences between Caucasian populations, and between Caucasians and Japanese.

Various criteria have been proposed for using vertebral measurements to identify vertebral fractures. It is known that the normal distributions of vertebral heights and ratios vary with location within the spine. However, very little is known regarding the degree to which differences in these parameters may exist between populations. We report the vertebra-specific distributions of vertebral dimensions and ratios for Japanese-Americans, and compare these values to published data for Caucasians. The mean Japanese vertebral heights were 1 to 2 mm shorter than Caucasians, which may be due in part to the shorter stature of Japanese. However, differences in mean values were also observed between Caucasian populations. Furthermore, anterior/posterior vertebral height ratios differed between Caucasian studies, and between races. Additional studies are needed to determine to what degree these differences are due to technical and biological factors before criteria derived from one population can be used for identifying vertebral fractures in other populations of the same, or different, race.

Adult↗
PubMed1990

Intermittent cyclical etidronate treatment of postmenopausal osteoporosis.

BACKGROUND: To determine the effects of etidronate (a bisphosphonate that inhibits osteoclast-mediated bone resorption) in the treatment of postmenopausal osteoporosis, we conducted a prospective, two-year, double-blind, placebo-controlled, multicenter study in 429 women who had one to four vertebral compression fractures plus radiographic evidence of osteopenia. METHODS: The patients were randomly assigned to treatment with phosphate (1.0 g) or placebo twice daily on days 1 through 3, etidronate (400 mg) or placebo daily on days 4 through 17, and supplemental calcium (500 mg) daily on days 18 through 91 (group 1, placebo and placebo; group 2, phosphate and placebo; group 3, placebo and etidronate; and group 4, phosphate and etidronate). The treatment cycles were repeated eight times. The bone density of the spine was measured by dual-photon absorptiometry, and the rates of new vertebral fractures were determined from sequential radiographs. RESULTS: After two years, the patients receiving etidronate (groups 3 and 4) had significant increases in their mean (+/- SE) spinal bone density (4.2 +/- 0.8 percent and 5.2 +/- 0.7 percent, respectively; P less than 0.017). The rate of new vertebral fractures was reduced by half in the etidronate-treated patients (groups 3 and 4 combined) as compared with the patients who did not receive etidronate (groups 1 and 2 combined) (29.5 vs. 62.9 fractures per 1000 patient-years; P = 0.043); the effect of treatment was most striking in the subgroup of patients with the lowest spinal bone mineral density at base line, in whom fracture rates were reduced by two thirds (42.3 vs. 132.7 fractures per 1000 patient-years; P = 0.004). The addition of phosphate provided no apparent benefit. There were no significant adverse effects of treatment. CONCLUSIONS: Intermittent cyclical therapy with etidronate for two years significantly increases spinal bone mass and reduces the incidence of new vertebral fractures in women with postmenopausal osteoporosis.

Aged↗
PubMed1990

A critical review of bone mass and the risk of fractures in osteoporosis.

The usefulness of various bone mineral measurement techniques is a subject of current controversy. In order to explore whether disparate conclusions may have arisen from differences in analytic methodology, data from published reports of bone mass and nonviolent fractures have been reanalyzed in terms of fracture risk. In the large majority of studies, reduced bone mass was associated with an increased risk of fractures. However, the magnitude of the relationship varied much more among cross-sectional studies than among prospective studies, suggesting that bias related to subject selection and/or postfracture bone loss may have strongly influenced the cross-sectional findings. We conclude that more emphasis should be given to the results of prospective studies, and that more attention should be paid to subject selection in all investigations. Analyzing and presenting results in terms of fracture risk would probably reduce the level of confusion in the field and provide more clinically relevant information. These issues are also applicable to studies of potential fracture risk factors other than bone mass, such as bone structure and bone quality.

Aged↗
PubMed1990

Fracture prediction models for osteoporosis prevention.

Fracture prediction models have been developed that can estimate an individual's cumulative or lifetime fracture risk on the basis of bone mineral measurements and other factors. Examples illustrate how estimates of cumulative fracture risk might be influenced by initial age and level of bone mass, as well as by anticipated bone loss rate. New data regarding bone loss rates, fracture costs, and fracture risk factors should be incorporated to improve the accuracy of existing models. Such models could then be used for cost-benefit analysis to explore optimal treatment strategies.

Bone Density↗
PubMed1989

Comparison of cross-sectional and longitudinal measurements of age-related changes in bone mineral content.

Age-related, postmenopausal bone loss was examined among a cohort of Japanese-American women living in Hawaii. None of the women were using estrogens or thiazides. Cross-sectional and longitudinal measurements of bone mineral content were compared at the calcaneus, the proximal radius, and the distal radius. Cross-sectional measurements were also available for the lumbar spine. The longitudinal data showed a slowing rate of bone loss with increasing age at the radius sites. By contrast, the cross-sectional data suggested constant rates of bone loss for all ages at both radius sites and the spine. The calcaneus demonstrated a complex pattern of bone loss in both cross-sectional and longitudinal analyses. The loss rates among women in their fifties were greater than for those in their sixties. From the middle sixties onward calcaneal bone loss remained essentially constant. Because of the sustained bone loss, however, women in their seventies were actually losing greater percentages of their calcaneal bone mineral than they had in their sixties.

Aged↗
PubMed1989

Perspectives: methodologic issues in evaluating risk factors for osteoporotic fractures.

Techniques for measuring bone mineral content (BMC) were developed for the purpose of providing an objective and noninvasive indication of bone strength (or lack thereof) and fracture risk, to the extent that strength relates to bone mass. As such, BMC measurements could help to (1) identify those who are most likely to experience nonviolent fractures in the future and who would therefore benefit most from preventive measures, (2) improve their treatment compliance, and (3) monitor the efficacy of treatments intended to reduce bone loss. All these potential uses require that the measurement provide an indication of fracture risk (probability of fractures). During the past 10-15 years there have been conflicting reports regarding the association of reduced BMC with nonviolent fractures. Some authors have criticized the usefulness of BMC measurements, whereas others have questioned the value of one or more techniques. However, the epidemiology of osteoporosis has only recently been subjected to rigorous study. The use of appropriate statistical methods for relating fracture risk to bone mass may be no more widely practiced in osteoporosis epidemiology today than it was for studying risk factors (e.g., blood pressure) in cardiovascular epidemiology during the 1960s. The intent of this article is to explore three areas that may have contributed to controversy in the study of bone mass and fracture occurrence: (1) perspective of the investigators, (2) study design, and (3) analytic methodology. Although the focus of this paper is on bone mass, these considerations are equally applicable to some investigations of other risk factors for osteoporotic fractures (e.g., bone architecture, bone turnover and loss rate, or biochemical markers of bone loss).

Bone Density↗