Aspiration pneumonia: With special reference to pathological and epidemiological aspects, a review of the literature

Summary aspiration plays an important role in the pathogenesis of bacterial pneumonia in the elderly. Defense of the airway is impaired in the elderly by alteration in respiratory mechanics; decreased mucociliary clearance and immunosenescence. And, the number of microorganisms in the oral cavity of the elderly is usually larger than that of young adults because of gradual reduction in production of saliva. A relationship between poor oral health and respiratory disease has been suggested by a number of recent microbiologic and epidemiologic studies, especially in elder subjects; who requiring help with feeding, wearing denture/edentate, with periodontal disease, and so on. Several researchers have reported that using professional oral health care (POHC) can prevent pneumonia. Oral/respiratory mucosal tissues produced cytokine that stimulated by oral microorganisms and were altered expression of various cell adhesion molecules on their surface in response to cytokine stimulation. Then, aspiration pneumonia histopathologically characterized with inflammatory response including macrophage infiltration was caused by aspiration of oral microorganisms, acid and food particle. In conclusion, silent aspiration may be a key risk factor for the pathogenesis of pneumonia in the elderly patients with poor oral hygiene.