Pneumonia is a common infection that leads to frequent hospitalizations and primary healthcare visits. Previous smaller studies have indicated high prevalence of undiagnosed diabetes mellitus (DM) and increased subsequent risk of coronary heart disease (CHD) among patients with pneumonia. However, previous studies have not used nationwide data that include diagnoses from primary healthcare settings, where most pneumonias are treated. The aim of this study was to examine whether pneumonia is associated with subsequent DM and CHD. This was an open nationwide cohort study of adults 35–75 years of age in Sweden 2007–2018, including national registers and population-based primary healthcare data. The outcomes were DM and CHD, and individuals with outcomes diagnosed before the index date (including 2002–2005) were excluded. The index date was set as the first pneumonia diagnosis or the first healthcare contact (in those without pneumonia) during the study period. Cox regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI) while adjusting for potential confounders. A total of 4,580,606 individuals without previously diagnosed DM and 4,661,052 individuals without previously diagnosed CHD were included; of these, 348,024 individuals were diagnosed with DM and 295,592 with CHD during follow-up, respectively. Pneumonia preceded DM in 104,598 (30.1%) and CHD in 94,087 (31.8%) individuals. Compared with no diagnosis, pneumonia was associated with an age-adjusted HR of 1.12 (95% CI 1.11–1.13) for DM and 1.18 (95% CI 1.17–1.19) for CHD. In the full model, pneumonia was associated with a HR of 1.11 (95% CI 1.10–1.12) for both outcomes. Several complementary analyses were conducted, showing significant associations across most age-groups, in both sexes, across different follow-up periods (e.g. <1 year and ≥ 10 years), and in patients diagnosed with pneumonia in primary healthcare settings. This nationwide study found that pneumonia is associated with subsequent DM and CHD. The findings indicate that pneumonia has a potential role as a clinical predictor of DM or CHD, including in primary healthcare settings, which warrants further clinical studies.
Jansåker et al. (Mon,) studied this question.