The incidence of pleural infections appears to be increasing in Western countries for unclear reasons. The aim of the study was to describe the incidence and treatment patterns of pleural infections in Finland over three decades.

Data regarding each treatment episode for pleural infections in the Finnish special medical care between January 1994 and December 2016 was obtained from a national database and compared to the demographics of Finnish residents obtained from the national census bureau. The annual incidence rates, type of treatment given, as well as the lengths of the hospitalization were analyzed.

A total of 28,463 episodes were reported, of which 55% were inpatient episodes. Of these, 76% concerned males, and the median age of patients was 60 (interquartile range 49–70) years. The overall incidence of pleural infections was 23.4 per 100.000 patient-years, with a male-to-female -ratio of 3.3:1. The annual incidence rates increased throughout the study period with an average annual percentage change of +11.4% (95% CI ±7.4%). The highest incidence rates (>200 per 100.000 patient-years) were observed in men aged 80 or more. Altogether 88% of patients were treated conservatively. The proportion of patients treated by mini-invasive surgery significantly increased during study period (0–5.9%, p < 0.001) and was associated with shorter hospitalization (median 6 [interquartile range 4–12] days) than open surgery (median 7 [4.5–13] days) (p < 0.001).

The incidence of pleural infections has increased significantly over the previous decades in Finland and appears to be higher than previously reported, particularly in elderly men.