METHODOLOGY OF MEDOS MULTICENTER STUDY OF HIP FRACTURE INCIDENCE - VALIDITY AND RELEVANCE CONSIDERATIONS

The Mediterranean osteoporosis (MEDOS) study was carried out in 14 cen tres from six countries in Southern Europe to determine the incidence rates and risk factors associated with hip fracture over the age of 50 years. This paper discusses both the validity and relevance of the da ta, that is, whether the number of collected cases of hip fracture and the size and age distribution of the population are representative of the population as a whole, and whether the incidence measures used in the study are suitable for comparing the risk of hip fracture between populations and for predicting future risk within populations. Five m easures of risk were assessed at each centre: crude incidence over the age of 50 years; age-standardised incidence; risk increase/fracture d oubling time by age; computed incidence at 50 years; and excess morbid ity. Three standardised populations were used for comparison: the MEDO S population (incidences standardised to the overall age and sex distr ibution of all the participating centres); the weighted MEDOS populati on (only including the age range 60 to 84 years); and the Swedish popu lation at the start of the study. The MEDOS study showed that the inci dence of hip fracture increased exponentially with age in both sexes a t all centres. The regression slope of incidence against age was affec ted by the age distribution of the population, but not by the absolute size of the population. Methods used to define the population of the catchment areas did not introduce errors of a greater magnitude than w ould the occasional addition or removal of single fracture cases. Crud e incidences and standardised rates were robust as well as the increas e in risk with age. There is reason to believe that the degree of impe rfections in data capture is less than the statistical random variatio n. The use of several indices of incidence for different purposes is d iscussed.