Intensive care unit admissions for community-acquired pneumonia are seasonal but are not associated with weather or reports of influenza-like illness in the community

PurposeThe aims of this study were to determine if there is seasonal variation in the number of intensive care unit (ICU) admissions for community-acquired pneumonia (CAP) and if there is a relationship between these admissions and weather or reports of influenza-like illness in the community.Materials and MethodsIn this time series analysis in 3 medical-surgical ICUs (8, 13, and 20 beds) in the Vancouver region, we included patients admitted to adult ICUs for CAP between January 2002 and March 2006. We used Poisson regression to analyze the association between weekly number of ICU admissions for CAP, and average temperature, range in temperature, total precipitation, and cases of influenza-like illness/100 physician visits reported by sentinel physicians in the community.ResultsIn 740 patients admitted to ICUs for CAP, admissions peaked each year in the winter-spring months. In multivariate models, a sine function with a single annual peak was independently associated with number of patients admitted to ICU for CAP (rate ratio [95% confidence interval], 1.12 [1.00, 1.26]), but neither the weather measurements nor the weekly rate of reported influenza-like illness was significantly associated.ConclusionIntensive care unit admissions for CAP are seasonal, but neither weather measurements nor weekly rate of reported influenza-like illness in the community is associated with these admissions.