Delirium: This is a common condition in elderly patients, characterized by acute onset of confusion, altered level of consciousness, and disorganized thinking. The patient's symptoms of waking up confused and yelling could be indicative of delirium, which can be caused by various factors such as infections, medications, or environmental changes.

Dementia with agitation: Patients with dementia can exhibit agitation and confusion, especially in the morning. This could be due to sundowning, a phenomenon where dementia patients become more agitated and confused in the late afternoon or early morning.
Sleep disorders: Sleep apnea, insomnia, or other sleep disorders can cause confusion and disorientation upon waking.
Medication side effects: Certain medications, such as sedatives or antidepressants, can cause confusion and altered mental status as a side effect.

Hypoglycemia: Low blood sugar can cause confusion, agitation, and altered mental status, and is a medical emergency that requires prompt treatment.
Stroke or transient ischemic attack (TIA): A sudden onset of confusion and altered mental status can be a sign of a stroke or TIA, which requires immediate medical attention.
Seizure: A seizure can cause post-ictal confusion and altered mental status, and may require urgent medical evaluation.
Infection: Infections such as urinary tract infections or pneumonia can cause confusion and altered mental status, especially in elderly patients.

Neurodegenerative diseases: Rare neurodegenerative diseases such as frontotemporal dementia or Creutzfeldt-Jakob disease can cause confusion and altered mental status.
Endocrine disorders: Certain endocrine disorders such as hyperthyroidism or hypothyroidism can cause confusion and altered mental status.
Vitamin deficiencies: Deficiencies in vitamins such as B12 or thiamine can cause confusion and altered mental status.