Melton, L. Joseph

OBJECTIVE: This study investigates temporal trends in the prevalence and incidence of persistent proteinuria among people with adult-onset diabetes (age > or =40 years). RESEARCH DESIGN AND METHODS: The complete community-based medical records of all Rochester, Minnesota, residents with a diagnosis of diabetes or diabetes-like condition from 1945 through 1989 were reviewed to determine whether they met National Diabetes Data Group (NDDG) criteria. All confirmed diabetes cases residing in Rochester on 1 January 1970 (n = 446), 1980 (n = 647), and/or 1990 (n = 940) were identified. The medical records of these prevalence cases were reviewed from the time of the first laboratory urinalysis value to the last visit, death, or 1 April 1992 (whichever came first) for evidence of persistent proteinuria (two consecutive urinalyses positive for protein, with no subsequent negative values). Similarly, the medical records of all 1970-1989 diabetes incidence cases (n = 1,252) were reviewed to investigate temporal changes in 1) the likelihood of having persistent proteinuria before the date NDDG criteria was met, i.e., baseline; 2) the risk of persistent proteinuria after baseline; and 3) the relative risk of mortality associated with persistent proteinuria. RESULTS: The proportion of diabetes prevalence cases with persistent proteinuria on or before the prevalence date declined from 20% in 1970 to 11% in 1980 and 8% in 1990. Among the 1970-1989 diabetes incidence cases, 77 (6%) had persistent proteinuria on or before baseline; the adjusted odds declined by 50% with each 10-year increase in baseline calendar year (P<0.001). Among individuals free of persistent proteinuria at baseline, 136 subsequently developed persistent proteinuria; the estimated 20-year cumulative incidence was 41% (95% CI 31-59); the adjusted risk did not differ as a function of baseline calendar year. Survival of individuals with persistent proteinuria relative to those without was reduced but did not differ by baseline calendar year. CONCLUSIONS: The prevalence of persistent proteinuria among people with adult-onset diabetes in Rochester, Minnesota, declined 60% between 1970 and 1990. The decline appears because of a decrease in the proportion of diabetes incidence cases with persistent proteinuria before baseline rather than secular declines in the risk of persistent proteinuria after baseline or secular increases in the risk of mortality associated with persistent proteinuria. Similarity over time in age and fasting glucose at baseline, and at prevalence dates, is evidence that earlier detection of diabetes is not the sole explanation for the decline.

Although osteoporosis has traditionally been considered a disease of women, men also incur substantial bone loss with aging, and elderly men have age-specific hip fracture incidence rates and vertebral fracture prevalence rates that are at least half those in women. Early postmenopausal bone loss (which results in the syndrome of type I osteoporosis) is due to the direct skeletal consequences of estrogen deficiency, manifested by an increase in bone resorption without an adequate increase in bone formation. Recent evidence indicates that even late postmenopausal bone loss (type II or ‘senile’ osteoporosis) in women may be due to estrogen deficiency. In particular, the late consequences of estrogen deficiency in elderly women result in abnormalities in calcium homeostasis and increases in parathyroid hormone secretion, leading to increased bone resorption and bone loss. The etiology of bone loss in aging men has remained relatively unclear. Recent evidence from a male deficient in estrogen receptor-alpha and in two males with aromatase deficiency indicate that estrogen may play a significant role in bone metabolism in men. Moreover, several large epidemiologic studies have found that bone mineral density correlates better with serum estrogen than testosterone in aging men. Thus estrogen deficiency may lead to bone loss in men.

Abstract A leading theory suggests that decreasing activity and muscle mass is the main cause of age-related bone loss. However, in a population-based study of 375 women and 325 men (age, 21–97 years), we failed to find a close correspondence between these variables and changes in bone strength with aging. Introduction: It has been suggested that bone strength is homeostatically adapted to habitual skeletal loading conditions and that bone loss could, therefore, result simply from age-related reductions in physical activity and muscle mass, but this notion has not been explored in detail. Materials and Methods: In a stratified random sample of Rochester, MN, women and men 21–97 years of age, indices of bone strength, flexural rigidity (EI), and axial rigidity (EA) were estimated from central QCT measurements at the femoral neck and lumbar spine and pQCT measurements at the ultradistal radius, whereas habitual skeletal loading was assessed using lean body mass, total skeletal muscle mass (TSM), body weight, and physical activity. Using regression analysis, we tested the hypothesis (Ho) that bone strength per unit load did not vary with age. Results and Conclusions: In these cross-sectional data, the null hypothesis of no age-related change was rejected in 72% of the strength-to-load ratios tested. For example, the ratio of femoral neck EI to TSM increased by 0.19%/year in women (p =0.008) and by 0.49%/year in men (p < 0.001). There was no close correspondence between changes in habitual load and changes in bone strength, nor any consistent pattern. Moreover, interindividual variation in the strength-to-load ratios was substantial. These data suggest that the notion of reduced skeletal loading as the primary basis for age-related bone loss is oversimplified.

Abstract Osteoporosis is widely viewed as a major public health concern, but the exact magnitude of the problem is uncertain and likely to depend on how the condition is defined. Noninvasive bone mineral measurements can be used to define a state of heightened fracture risk (osteopenia), or the ultimate clinical manifestation of fracture can be assessed (established osteoporosis). If bone mineral measurements more than 2 standard deviations below the mean of young normal women represent osteopenia, then 45% of white women aged 50 years and over have the condition at one or more sites in the hip, spine, or forearm on the basis of population-based data from Rochester, Minnesota. A smaller proportion is affected at each specific skeletal site: 32% have bone mineral values this low in the lumbar spine, 29% in either of two regions in the proximal femur, and 26% in the midradius. Although this overall estimate is substantial, some other serious chronic diseases are almost as common. More importantly, low bone mass is associated with adverse health outcomes, especially fractures. The lifetime risk of any fracture of the hip, spine, or distal forearm is almost 40% in white women and 13% in white men from age 50 years onward. If the enormous costs associated with these fractures are to be reduced, increased attention must be given to the design and implementation of control programs directed at this major health problem.

Abstract We studied whether oophorectomy performed after menopause is associated with an increased risk of hip or vertebral fractures in 6295 Study of Osteoporotic Fractures participants. There was no association between postmenopausal oophorectomy and the risk of hip or vertebral fractures. Introduction: Bilateral oophorectomy after natural menopause has been associated with an increased risk of osteoporotic fractures, potentially because of a decline in serum estradiol and testosterone levels after the oophorectomy. We prospectively tested this hypothesis in the Study of Osteoporotic Fractures (SOF). Materials and Methods: We studied 6295 white women ⩾65 years of age participating in the SOF who were not taking estrogen therapy at baseline. Hip fracture analyses included 708 hip fractures; vertebral fracture analyses included 267 incident vertebral fractures. Baseline serum estradiol and free testosterone values were available in a small subset of participants. Results and Conclusion: There were no significant differences in age, weight, or BMD between the women who underwent postmenopausal oophorectomy (n = 583) and those who did not (n = 5712). Free testosterone levels were significantly lower among women who had a postmenopausal oophorectomy. A history of postmenopausal oophorectomy was not associated with an increased risk of hip (hazard ratio [HR] = 1.1; 95% CI = 0.9-1.5) or vertebral fracture (HR = 0.7; 95% CI = 0.5-1.2). The relationship between oophorectomy and hip fracture was not altered by adding serum estradiol level (HR = 1.3; 95% CI = 0.5-3.2) or serum free testosterone level (HR = 1.7; 95% CI = 0.8-3.7) to the model. In summary, postmenopausal oophorectomy was not associated with an increased risk of hip or vertebral fracture in this cohort. These results are in contrast to previous findings, suggesting that the relationship between postmenopausal oophorectomy and fractures is not fully elucidated and that incidental oophorectomy after menopause should still be considered carefully in each potential patient.

Abstract Long-term fracture prediction using bone mineral density remains controversial, as does the additional contribution from assessing bone turnover or clinical risk factors. We measured bone mineral density at various sites, along with biochemical markers of bone turnover, sex steroid levels, and over 100 clinical variables, at baseline on an age-stratified sample of 304 Rochester, MN women in 1980. The 225 postmenopausal women were subsequently followed for 3146 person-years (median, 16.2 years per subject), wherein they experienced 302 new fractures: 81% resulted from minimal or moderate trauma and 60% of these involved the proximal femur, thoracic or lumbar vertebrae, or distal forearm. Accounting for multiple fractures per subject, these osteoporotic fractures together were best predicted by baseline femoral neck bone mineral density (age-adjusted hazard ratio [HR] per SD decrease, 1.37; 95% CI, 1.10–1.70); 19 moderate trauma forearm fractures were best predicted by distal radius bone mineral content, whereas 28 hip fractures and 100 vertebral fractures were best predicted by femoral neck bone mineral density. Femoral neck bone mineral density performed comparably in predicting osteoporotic fracture risk within the first decade of follow-up (HR, 1.38; 95% CI, 1.10–1.74) as well as more than 10 years after baseline (HR, 1.39; 95% CI, 1.05–1.84). The older biochemical markers were not associated with fractures, but serum “free” estradiol index was independently predictive of short- and long-term fracture risk. Consistent clinical risk factors were not identified, but statistical power was limited. Identifying patients at increased long-term risk of fracture is challenging, but it is reassuring that femoral neck bone mineral density can predict osteoporotic fractures up to 20 years later.

Abstract The relationship between BMD and fracture risk was estimated in a meta-analysis of data from 12 cohort studies of ∼39,000 men and women. Low hip BMD was an important predictor of fracture risk. The prediction of hip fracture with hip BMD also depended on age and z score. Introduction: The aim of this study was to quantify the relationship between BMD and fracture risk and examine the effect of age, sex, time since measurement, and initial BMD value. Materials and Methods: We studied 9891 men and 29,082 women from 12 cohorts comprising EVOS/EPOS, EPIDOS, OFELY, CaMos, Rochester, Sheffield, Rotterdam, Kuopio, DOES, Hiroshima, and 2 cohorts from Gothenburg. Cohorts were followed for up to 16.3 years and a total of 168,366 person-years. The effect of BMD on fracture risk was examined using a Poisson model in each cohort and each sex separately. Results of the different studies were then merged using weighted coefficients. Results: BMD measurement at the femoral neck with DXA was a strong predictor of hip fractures both in men and women with a similar predictive ability. At the age of 65 years, risk ratio increased by 2.94 (95% CI = 2.02-4.27) in men and by 2.88 (95% CI = 2.31-3.59) in women for each SD decrease in BMD. However, the effect was dependent on age, with a significantly higher gradient of risk at age 50 years than at age 80 years. Although the gradient of hip fracture risk decreased with age, the absolute risk still rose markedly with age. For any fracture and for any osteoporotic fracture, the gradient of risk was lower than for hip fractures. At the age of 65 years, the risk of osteoporotic fractures increased in men by 1.41 per SD decrease in BMD (95% CI = 1.33-1.51) and in women by 1.38 per SD (95% CI = 1.28-1.48). In contrast with hip fracture risk, the gradient of risk increased with age. For the prediction of any osteoporotic fracture (and any fracture), there was a higher gradient of risk the lower the BMD. At a z score of -4 SD, the risk gradient was 2.10 per SD (95% CI = 1.63-2.71) and at a z score of -1 SD, the risk was 1.73 per SD (95% CI = 1.59-1.89) in men and women combined. A similar but less pronounced and nonsignificant effect was observed for hip fractures. Data for ultrasound and peripheral measurements were available from three cohorts. The predictive ability of these devices was somewhat less than that of DXA measurements at the femoral neck by age, sex, and BMD value. Conclusions: We conclude that BMD is a risk factor for fracture of substantial importance and is similar in both sexes. Its validation on an international basis permits its use in case finding strategies. Its use should, however, take account of the variations in predictive value with age and BMD.

Abstract In a population-based, cross-sectional study, we assessed age- and sex-specific changes in bone structure by QCT. Over life, the cross-sectional area of the vertebrae and proximal femur increased by ∼15% in both sexes, whereas vBMD at these sites decreased by 39–55% and 34–46%, respectively, with greater decreases in women than in men. Introduction: The changes in bone structure and density with aging that lead to fragility fractures are still unclear. Materials and Methods: In an age- and sex-stratified population sample of 373 women and 323 men (age, 20–97 years), we assessed bone geometry and volumetric BMD (vBMD) by QCT at the lumbar spine, femoral neck, distal radius, and distal tibia. Results: In young adulthood, men had 35–42% larger bone areas than women (p < 0.001), consistent with their larger body size. Bone area increased equally over life in both sexes by ∼15% (p < 0.001) at central sites and by ∼16% and slightly more in men at peripheral sites. Decreases in trabecular vBMD began before midlife and continued throughout life (p < 0.001), whereas cortical vBMD decreases began in midlife. Average decreases in trabecular vBMD were greater in women (−55%) than in men (−46%, p < 0.001) at central sites, but were similar (−24% and −26%, respectively) at peripheral sites. With aging, cortical area decreased slightly, and the cortex was displaced outwardly by periosteal and endocortical bone remodeling. Cortical vBMD decreased over life more in women (∼25%) than in men (∼18%, p < 0.001), consistent with menopausal-induced increases in bone turnover and bone porosity. Conclusions: Age-related changes in bone are complex. Some are beneficial to bone strength, such as periosteal apposition with outward cortical displacement. Others are deleterious, such as increased subendocortical resorption, increased cortical porosity, and, especially, large decreases in trabecular vBMD that may be the most important cause of increased skeletal fragility in the elderly. Our findings further suggest that the greater age-related decreases in trabecular and cortical vBMD and perhaps also their smaller bone size may explain, in large part, why fragility fractures are more common in elderly women than in elderly men.

Abstract Global aging superimposed on existing infectious diseases and trauma will aggravate competition for health care resources to diagnose and treat osteoporosis. Efforts to implement public health measures are needed, but the targeted approach to assessment and treatment of high-risk individuals must also be refined. Increases in the elderly population worldwide will cause a dramatic rise in osteoporotic fractures, but other age-related diseases will increase as well. Changes will be superimposed on existing public health problems (e.g., malaria, alcoholism), and these acute health care needs will take priority in some areas. Societies in most parts of the world may have to limit osteoporosis control to broad public health measures, and such efforts (e.g., calcium and vitamin D supplementation) should be supported. In these regions, clinical decision-making will generally be limited to treating patients with fractures (who presumably have already failed any public health measures in place), or in a few wealthy countries, to patients with low bone density identified by case-finding. Case-finding approaches will vary with the resources available, although unselective (mass) screening by bone densitometry is largely ineffective and unaffordable anywhere. The key to clinical decision-making on behalf of individuals will be an assessment of absolute fracture risk, and the tools needed to predict the risk of an osteoporotic fracture over the next 10 years are now being developed. These include bone density measures, but also incorporate other risk factors (e.g., fracture history, corticosteroid use), which may allow extension of fracture risk prediction to nonwhite populations and to men. Even with a universal risk prediction tool, cost-effective treatment thresholds will vary by country based on the level of fracture risk in the region and on the resources available for health care. To better compete for these resources, efforts should be made to lower the cost of osteoporosis interventions. Additionally, evidence is needed that these interventions are really effective in reducing fractures in the community.