Risk factors of pneumonia in persons with and without Alzheimer’s disease: a matched cohort study

BACKGROUND: Pneumonia is a very common infection in the cognitively impaired adult population, often leading to long-term deterioration, in physical and cognitive performance. Evidence is lacking on whether chronic comorbidities and drug use are risk factors for pneumonia in persons with Alzheimer’s disease (AD). The objective of this study was to investigate the risk factors of pneumonia in community dwellers with and without AD. METHODS: We performed a retrospective register-based study utilizing the Medication Use and Alzheimer’s disease (MEDALZ) cohort, which is based on Finnish nationwide healthcare registers and includes all community dwellers who received a verified clinical diagnosis of AD between 2005 to 2011. This study comprised 69,350 persons with AD and 69,350 persons without AD matched by age, gender, and region of residence. Association between comorbidities, drug use, and hospitalization due to pneumonia were assessed using Cox Regression. RESULTS: During the follow-up, 25.0% (n = 17,105) of the AD cohort and 15.8% (n = 10,966) of the non-AD cohort were hospitalized due to pneumonia. Persons with AD had a higher risk of pneumonia also after adjusting for comorbidities (HR 1.76, 95% CI 1.71–1.80). Previous pneumonia was the strongest risk factor for pneumonia in both cohorts. All comorbidities and drug use excluding biological product use were associated with a higher risk of pneumonia, but stronger associations were observed in the non-AD cohort. The risk of hospitalization following psychotropic drug use was proportional to the number of psychotropics utilized. CONCLUSIONS: Pneumonia is a serious, potentially life-threatening illness, and risk factors for pneumonia include several potentially avoidable drugs. In addition, good care of existing comorbidities might prevent pneumonia and related hospitalization. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12877-023-03940-z.