Introduction and objectiveThe growing population of the elderly, as well as the occurrence of coexisting diseases and polypharmacy, is the reason why diseases of patients aged $65 years belong to the major issues of the contemporary medicine. Among the most frequent diseases of the elderly, there are respiratory system diseases. They are difficult to diagnose because of the patient group specificity, which is the reason for increased mortality among seniors, caused by underdiagnosis. The study objective was to assess the factors influencing spirometry results in hospitalized patients aged ≥65 years with respiratory system disorders.Material and methodsIn the research, 217 (100%) patients aged ≥65 years who underwent spirometry at the Regional Medical Center of the Jelenia Góra Valley Hospital in Poland were analyzed. In the statistical analysis, the STATISTICA 9.1 program, the t-test, the Shapiro–Wilk test, the ANOVA test, and the Scheffé’s test were applied.ResultsThe majority of the patients (59.4%) were treated in the hospital. The most frequent diagnosis was malignant neoplasm (18%). The study showed a statistically significant dependence between the forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and FEV1/FVC parameters and the time of hospitalization, as well as between the FVC and FEV1 parameters and the age of patients. The FVC parameter values turned out to be dependent on the main diagnosis. Highest results were noted in patients with the diagnosis of sleep apnea or benign neoplasm. A low FVC index can reflect restrictive ventilation defects, which was supported by the performed analyses. Highest FEV1/FVC values were observed in nonsmokers, which confirms the influence of nicotine addiction on the incidence of respiratory system diseases.ConclusionThe respondents’ sex and the established diagnosis statistically significantly influenced the FVC index result, and the diet influenced the FEV1/FVC parameter result.