T IS GENERALLY agreed that osteoporosis is a disease char-I acterized by abnormalities in the amount and structural arrangement of bone tissue which leads to impaired skeletal strength and an undue susceptibility to fractures.") These qualities are difficult to measure directly, however, and they bear a continuous relationship with fracture risk in any event. Consequently, the prevalence of osteoporosis depends on some arbitrarily chosen cut-off level of a surrogate measure, such as bone mineral density (BMD). Based on the recommendation that the cut-off level be set at 2 SD below the mean of normal young women,") it was estimated that 45% of postmenopausal white women in the United States were at increased risk of fracture as a result of low BMD in the hip, spine, or forearm. (3) Recently, however, an expert panel convened by the World Hcalth Organization devised an operational definition of osteoporosis that is more ~omprehensive.'~) As reviewed elsewhere,(') low bone mass (or osteopenia) is now defined as BMD more than 1 SD below the young normal mean but less than 2.5 SD below. Women with bone density levels more than 2.5 SD below the young normal mean are presumed to have osteoporosis at the tissue level, even in the absence of a confirmatory biopsy. To provide some comparability with older definitions, the subset of women with presumptive osteoporosis who have a history of one or more fragility fractures are deemed to have "established" osteoporosis.What influence do these revised diagnostic criteria have on the estimated number of affected women in this country? Again, data from an age-stratified random sample of Rochester, Minnesota, women were extrapolated national-IY.'~) Bonc density was assessed in the neck and intertrochanteric regions of the proximal femur and iri the lumbar spine by dual photon absorptiometry and in the midradius by single photon absorptiometry. The proportion of women in each age group with bone density below specified levels at any of these skeletal sites was projected to the population structure of United States white women in 1990. The pro-portion of postmenopausal women ( 2 5 0 years of age) in each risk category defined by the WHO panel was then summed across age groups.As can be seen in Fig. 1 , most women under age 50 have normal bone density at all four skeletal sites, and osteoporosis is rare. With advancing age, however, the population becomes smaller and a greater proportion has osteopenia or osteoporosis. Among women age 80 years and over, for example, only 3% have normal BMD at all four sites, 27% have osteopenia at one skeletal site or another, and 70% have osteoporosis. Sixty percent of the latter group (42% altogether) have experienced one or more fractures of the proximal femur, vertebra, distal forearm, proximal humerus, or pelvis as judged from the Rochester data. Overall, an estimated 16.8 million (54%) postmenopausal white women in the United States have osteopenia and another 9.4 million (30%) have osteoporosis. About 4.8 million women (51% of the osteoporotic...

Bone mass and its mineral content are under genetic control. The vitamin D receptor (VDR) gene has been shown to be a major locus for genetic effects on bone mineral density (BMD), and polymorphisms in this gene accounted for a large proportion of genetic variance in BMD in an Australian population. In this study, we investigated whether similar associations are present in a North American population. We studied 139 normal healthy women (age 53.2 +/- 14.5, mean +/- SD) and 43 severely osteoporotic postmenopausal women (age 65.8 +/- 5.9). In the 127 of them with complete genetic studies, the distribution of genotypes, determined by polymerase chain reaction on leukocyte DNA samples, agreed closely with that in the Australian population. BMD was strongly related to age and weight, and, thus was adjusted for these parameters prior to genetic analysis. We found that age modulated the effect of VDR genotypes on femoral neck BMD (FN-BMD) (TaqI, p = 0.036; BsmI, p = 0.118; ApaI, p = 0.041) such that the effect of genotype was greatest among younger (premenopausal) women and declined with age so that there was no discernible difference by age 70. Among the younger women, a high FN-BMD was associated with the TT (or aa or bb) genotype while low FN-BMD was associated with the tt (or AA or BB) genotype.(ABSTRACT TRUNCATED AT 250 WORDS)

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To explore possible changes in proximal femur (hip) fracture incidence over time, an earlier study among Rochester, Minnesota residents for 1928-1977 was updated through 1982. Reanalysis of data demonstrated rising age-adjusted rates for men over this time. Crude rates rose for women as well, but age adjusted rates leveled off in the mid-1950s, as did overall rates, since the majority of hip fractures were in women. Secular trends were primarily due to changes in the incidence of initial hip fractures associated with moderate trauma, the sort usually attributed to osteoporosis. No differences were noted in trends for cervical vs. intertrochanteric femur fractures; and, excluding the low values for 1928-1942, no significant trends were noted for women within various age groups. Our results for women conflict with estimates from a number of other studies, but these differences may provide a basis for hypothesis development.

Information on agricultural trauma is limited and difficult to find. Planning for effective prevention strategies and evaluation is compromised by lack of a good surveillance system. Several agencies and organizations have provided some data. Although their summation is at best an approximation of the real situation, a critical review of current data bases is presented. The literature is also reviewed attempting to characterize agricultural trauma. This characterization was classified into: 1) case descriptions, 2) reviews of general articles on the hazards of farming, and 3) descriptive surveys of agricultural injuries. A summary of the available literature still leaves a rather superficial understanding of the entire injury picture. A new approach to surveillance is necessary to overcome past deficiencies. A combined modality approach is suggested, utilizing on-site survey, mail survey, telephone interviewing, and medical record verification. Trial applications of two such systems in Minnesota are described.