pneumonia is related to oral health of the elderly and intensive care unit patients. However, studies on the relationship between overall oral health and pneumonia in the general population have been limited. the purpose of this study was to investigate the association between oral health and pneumonia using a nationwide population-based Korean cohort database. Data from 122,251 participants who underwent health screening and oral examinations in 2004 or 2005 were analyzed. Cox proportional hazard regression analysis was performed to evaluate the association between oral health and pneumonia. The risk of pneumonia increased significantly in groups with a higher number of dental caries and missing teeth, with respective adjusted hazard ratios (HRs) and 95% confidence interval (CI) of 1.265 (1.086-1.473; p = 0.0025) and 1.218 (1.113-1.332; p < 0.0001), and decreased significantly in frequent tooth brushing and regular professional dental cleaning groups, with respective adjusted HRs and 95% CI of 0.853 (0.786-0.926; p = 0.0001) and 0.920 (0.855-0.990; p = 0.0255). In addition, regardless of age and comorbidities, oral health status and oral hygiene behaviors were associated with pneumonia. the results indicate that improved oral health may reduce the risk of pneumonia in the general population. Pneumonia is a debilitating disease that can result in death in elderly individuals 1 and has been reported to be related to oral health 2. The oral cavity is a complex environment for multiple microorganisms and cytokines 3. In particular, aspiration of microorganisms and biological mediators such as cytokines and hydrolytic enzymes from the oral cavity can provoke inflammation and cause infections 4,5. The association between pneumonia and oral health has been examined in nursing homes, and the incidence of pneumonia has been reported to be lower in elderly populations receiving oral care 6. Besides, several studies have suggested that hospitalized intensive care unit (ICU) patients appear to benefit from daily oral cleansing 7,8. Oral hygiene can be improved through individual-based interventions 9. Daily personal oral hygiene behaviors such as tooth brushing are fundamental in the prevention of periodontal disease and bacterial plaque, which can respectively lead to tooth loss and dental caries 10,11. In addition, professional dental cleaning has been proven to reduce periodontal disease, dental caries, and tooth loss 12. Dentists recommend tooth brushing at least twice daily as well as regular dental visits for professional dental cleaning 13. While the link between pneumonia and oral health has been gaining increased attention, studies evaluating the relationship between overall oral health and pneumonia in the general population have been limited. The purpose of this study was to investigate the association between oral health and pneumonia using a nationwide population-based Korean cohort from the National Health Insurance Service-Health Screening (NHIS-HealS) database. Methods Data source. This study used the NHIS-H...