TRENDS IN THE EPIDEMIOLOGY OF IDDM DURING 1970-2020 IN FYN COUNTY, DENMARK

OBJECTIVE - To present an epidemiological model applicable to diabetes based on which prevalence rates are estimated from assumed rates of i ncidence and mortality of diabetes. Furthermore, this study illustrate s the model by analyzing epidemiological data on IDDM in a Danish popu lation during 1970-1990, with predictions of prevalence rates for 1990 -2020. RESEARCH DESIGN AND METHODS - The epidemiological model assumes known prevalence rates as well as incidence rates and mortality at a given time. Under assumed rates of incidence and mortality of IDDM and its complications, the prevalence rate is the dependent variable, est imated as a function of calendar time. We use epidemiological data on IDDM (operationally defined as insulin-treated diabetes with onset bef ore age 30 years), blindness, and nephropathy, as well as mortality, a s reported for 1973 and 1987 in Fyn County, Denmark. RESULTS - During 1970-1990, the prevalence of IDDM increased steadily because of increa sing incidence and decreasing risk of complications and mortality. The relative prevalence of patients with nephropathy increased, whereas t hat of blind patients decreased considerably. Under specified assumpti ons regarding the future levels of incidence of disease, complications , and mortality, it is estimated that the prevalence rate of IDDM in t he year 2020 will be 45-60% higher than the level in the year 1990. Th e relative prevalence of patients with nephropathy will increase furth er, whereas the relative prevalence of blind patients will remain cons tant at a low level. CONCLUSIONS - IDDM will represent an increasing p ublic health problem in Denmark during the next decades, with increasi ng overall prevalence rates and a rising proportion of patients with n ephropathy. The major determinant of this trend is increasing incidenc e, combined with declining mortality and declining risk of complicatio ns. It is strongly recommended that epidemiological models like the on e presented here be further developed and implemented at regional leve ls to provide data for the dimensioning of the current and future diab etes care systems.