Dementia can seem to worsen quickly because of infections, dehydration, medication side effects, depression, poor sleep, or a hospital stay. Constipation, pain, and hearing or vision problems can also make confusion worse. Big changes in environment or routine may trigger a sharp decline in how the person behaves. Sometimes the change is partly reversible if the underlying problem is treated. Any sudden worsening should be checked promptly, since it may not be just the dementia progressing.