Community-acquired pneumonia and influenza hospitalisations in northern Portugal, 2000-2005

Hospital admissions for pneumonia, one of the most frequent complications of influenza, are more common in children and the elderly and in individuals with chronic disease. Portugal’s Northern Health Region is one of the country’s five health regions, and its 3.3 million inhabitants represent approximately one third of the country’s population. We conducted a retrospective study to characterise the trend and the geographical distribution of hospitalisations due to pneumonia and influenza in public hospitals in northern Portugal. The distribution of the hospitalisations was investigated using exploratory techniques of spatial analysis based on data for pneumonia and influenza cases discharged from hospital between 2000 and 2005. There were 53,314 hospitalisations due to pneumonia and influenza during that period, representing an annual average hospitalisation rate of 274 per 100,000 inhabitants. The exploratory spatial analysis showed a moderate space dependence in the region (Moran’s Index=0.51, p<0.05). The local indicator of space association for each area allowed the detection of a cluster of 11 municipalities in two north-eastern districts that had higher rates of hospitalisation than the remaining regions. The results showed that the spatial distribution of hospital admissions for pneumonia and influenza is not homogeneous in northern Portugal, indicating that it is not coincidental. The significant spatial dependence highlights the need to perform further studies to examine the underlying causes of such distribution.