Neurological disorders like Parkinson’s disease can make swallowing an uncoordinated process. These disorders can make the patient choke on their food and develop pneumonia as particles enter the lungs.
Elderly persons with dementia, a neurodegenerative disease that affects memory, may be unable to properly initiate swallowing. He may just move the food around inside the mouth or let it collect in the gutter between the cheeks and gums. This disease eventually leads to degeneration of the swallowing center in the brain, making swallowing impossible. As memory also deteriorates, a patient may not comprehend that he is hungry and needs to eat. In some situations, the ability to swallow is intact but the patient develops behavioral changes that prevent him from eating enough food.
Many diseases, like acute infections, cause an acute change in taste sensation; for example, the patient frequently complains that food tastes bitter. Diseases that cause prolonged difficulty in breathing, like emphysema, may make an elderly patient so breathless that eating is often interrupted by the need to breathe. Nausea and vomiting accompanying many disease states prevent a patient from keeping food down. Elderly patients who are suffering from depression, which is either an isolated mood disorder or a component of dementia, may complain of poor appetite or just avoid eating altogether.
Medications also have their effects on eating. Many drugs cause loss of appetite, such as digoxin, a medication for heart failure. Antibiotics like metronidazole cause a bitter and metallic taste in the mouth. Sedatives make a patient excessively drowsy to eat properly and safely. Donepezil, a medication to slow down dementia, may cause nausea and gastrointestinal upset. Chemotherapy causes loss of appetite, nausea, and vomiting, and sometimes, ulcers in the mouth, which make eating even more challenging. Antipsychotic medications may result in rigidity and other movement problems, making chewing difficult.