Epidemiology of osteoporosis in women in southern Italy.

Studies on the distribution of bone mineral density (BMD) values in different age groups and in different populations are valuable for understanding the causes of the appreciable geographical variability in fracture incidence. We studied a population of southern Italy in an area where the incidence of hip fracture had been previously estimated. With a completion rate of 85%, we recruited a group of 264 women between 45 and 79 years of age, representative of non-institutionalized and active women in the population, and measured bone density both at the lumbar spine (L1-L4) and at the right femoral neck using a dual X-ray absorptiometry (DEXA) system. We report the age group distribution of BMD in this population. The elderly showed higher mineralization, as compared to an international pooled sample. The prevalence of osteoporosis among women of 50-79 years of age was 40%; the rate changed according to the measurement site. Our results show that a large proportion of women would not have been diagnosed as having osteoporosis if we had relied on a single measurement site. A very low percentage of cases (as low as 4% in the 50-59 years age group) was diagnosed at both sites. The lack of concordance in BMD estimate between measurement sites is significant at younger ages, with an almost dichotomous distribution of cases diagnosed either at the lumbar or femoral site, suggesting the hypothesis that distinct patterns of bone involvement and bone mass lowering exist and all eventually lead to systemic involvement. Longitudinal follow-up of this population should help address some of the questions raised by these results.