Effect of aging on cough and swallowing reflexes: implications for preventing aspiration pneumonia.

The impairment of airway protective reflexes, i.e., swallowing and cough reflexes, is thought to be one of the major causes for aspiration pneumonia in older people. Restoration of cough and swallowing reflexes in the elderly is key to preventing aspiration pneumonia in the elderly. Although, the medical literature has asserted that cough and swallowing are controlled primarily by the brainstem, recent advances in human brain imaging has provided evidence that cortical and subcortical structures play critical roles in cough and swallowing control. Because of their nature, reflexive cough and swallowing activate both sensory and motor areas in the cortex. In both protective reflexes, the sensory component, including sensory cortex in reflexive circuits, seems to be more vulnerable to aging than the motor component, including the motor cortex. Therefore, the strategy to restore cough and swallowing reflexes should be focused on compensations of sensory components in these reflexive circuits. Remedies to enhance sensory nerve terminals and sensory cortical areas related to these reflexes might be useful to prevent aspiration pneumonia in the elderly.