A multilevel time-series model for the incidence of AIDS cases in Spain

Objective. The main aim of this research is to study the quantitative evolu tion of the incidence of AIDS in the 19 Spanish Communities. The hypothesis is that incidence follows a multilevel autoregressive model, where each Co mmunity shows random variability around a general process. Method. On the basis of official data on the number of existing AIDS cases, an autorregressive multilevel time-series model was developed. Results and Conclusions. Analysis shows that the hypothesis is supported, i ndicating that overall AIDS incidence in Spain has already reached a maximu m and has a tendency to remain stable or to decline in future. Long term ex pected values have become stable in most Communities: a slight increase is expected only in Extremadura. However, this Community has a relatively spar se population, and its contribution on the overall Spanish incidence is sma ll. Long term expected values are estimated to be around 152.99 new cases per m illion inhabitants per year. This value is slightly smaller than the maximu m incidence, observed in 1994 (179.4 cases). (C) 2000 Elsevier Science Ltd. All rights reserved.