Background: Community-acquired pneumonia (CAP) is one of the leading causes of morbidity and mortality worldwide. It remains unknown whether recently introduced prevention strategies, such as vaccination, may have impacted its mortality. Moreover, it is important to understand whether these trends are similar for all patients or if some groups may have different outcomes. Methods: We evaluated the CAP hospitalization data for adult patients, from the Portuguese mainland Hospital diagnosis database. We included all patients discharged with CAP between 2010 and 2019. We assessed Hospital mortality for the whole population and according to age and gender. We also examined the monthly number of admissions and mortality. Results: We identified 462,910 CAP admissions, of which 54% were male (mean age 76.8 ± 14.5years). We divided our population into 4 age groups: 18-40years (3.2% of episodes); 41-65years (14.9%); 66-80years (31.6%); >80 years (50.2%). Mortality increased sharply with age, to more than 40% in older patients, highlighting the disproportionate burden of respiratory diseases in this age group. Although CAP mortality remained stable until 2016 (roughly 23%), a slight decreasing trend was noted afterwards (from 23.1 to 21.8%). In hospitalized patients, the relative risk of dying with CAP, consistently decreased during this period, from odds ratio 5.5, 95% CI 5.4–5.7 to odds ratio 4.3, 95% CI 4.2–4.4. As much as 25% of deaths related to CAP occurred during the first 48 h after hospital admission. While CAP admissions peaked in January, mortality was higher during the summertime. Conclusions: Community-acquired pneumonia remains associated with a high risk of death. Mortality increased with age from 40 years onwards. However, the relative risk of dying with CAP in the Hospital decreased during this decade. Graphical

Background: Community-acquired pneumonia (CAP) remains a leading cause of morbidity and mortality worldwide and a major driver of hospital admissions. Older adults are disproportionately affected, owing to immune senescence and a higher prevalence of chronic comorbidities. This study examined two decades (2000–2019) of adult hospital admissions for CAP in mainland Portugal. Methods: We analyzed adult CAP hospitalizations between 2000 and 2019 from the Portuguese Mainland Hospital Diagnosis National Database. We assessed all hospitalizations attributable to CAP over the 20 years, stratified by age group, and examined seasonal variation. Trends in hospital length of stay and in-hospital case fatality were evaluated. Results: Between 2000 and 2019, the adult CAP hospitalization rate in Portugal rose from 3.61 to 5.28 per 1000 persons-year. This was fostered by patients older than 80 years, who grew from 30.4% to 53.1% of CAP admissions. The mean age increased over time, from 70.1 ± 17.0 years to 77.7 ± 14.1 years. Hospitalization episodes of patients older than 85 years admitted for CAP increased fourfold. CAP-associated case fatality increased slightly, driven by patients older than 80 years. A modest decline was noted from 2016 to 2019 (from 23.1% to 21.8%). This was strongly correlated with mean age. Invasive mechanical ventilation was offered in a growing number of hospitalization episodes of CAP (from 3.1% in 2000 to 7.5% in 2019) but with significant age imbalance. Admissions peaked in January, whereas case fatality was highest during the summer months. Conclusions: These findings underscore the growing burden of CAP on healthcare systems, driven by an aging population and rising life expectancy. This has implications for both resource allocation and preventive strategies.