Risk factors for community-acquired pneumonia in adults: a population-based case-control study

Although community-acquired pneumonia (CAP) remains a major cause of hospit alization and death, few studies on risk factors have been performed. A pop ulation-based case-control study of risk factors for CAP was carried out in a mixed residential-industrial urban area of 74,610 adult inhabitants in t he Maresme (Barcelona, Spain) between 1993 and 1995, All patients living in the area and clinically suspected of having CAP at p rimary care facilities and hospitals were registered. In total, 205 patient s with symptoms, signs and radiographic infiltrate compatible with acute CA P participated in the study. They were matched by municipality, sex and age with 475 controls randomly selected from the municipal census. Risk factor s relating the subject's characteristics and habits, housing conditions, me dical history and treatments were investigated by means of a questionnaire. In the univariate analysis, an increased risk of CAP was associated with lo w body mass index, smoking, respiratory infection, previous pneumonia, chro nic lung disease, lung tuberculosis, asthma, treated diabetes, chronic live r disease, and treatments with aminophiline, aerosols and plastic pear-spac ers. In multivariate models, the only statistically significant risk factor s were current smoking of >20 cigarettes.day(-1) (odds ratio (OR)=2.77; 95% confidence interval (CI) 1.14-6.70 compared with never-smokers), previous respiratory infection (OR=2.73; 95% CI 1.75-4.26), and chronic bronchitis ( OB=2.22; 95% CI 1.13-4.37). Benzodiazepines were found to be protective in univariate and multivariate analysis (OR=0.46; 95% CI 0.23-0.94), This population-based study provides new and better established evidence on the factors associated with the occurrence of pneumonia in the adult commu nity.