Review Question - QID 213753

A 72-year-old woman is brought to her primary care doctor by her daughter with a chief concern of forgetfulness. The patient's daughter states that her mother has become more forgetful over the past several months. Recently, the patient got lost coming home from the gym she frequents. The daughter no longer allows her mother to cook as the patient has left the stove on a few times. She has also left her house doors unlocked when leaving on multiple occasions. The patient no longer goes to the casino with her friends, which was a previous favorite activity. The daughter has also noticed that her mother goes to bed early, but later she'll find her mother up late watching infomercials. The patient has been exercising less and has gained 10 pounds this past month. The patient states that she did not realize she was such a burden and feels ashamed that she has not been a better mother and wife to her husband who passed away recently. Her temperature is 97.8°F (36.6°C), blood pressure is 179/100 mmHg, pulse is 68/min, and respirations are 12/min. Physical exam is notable for a woman who moves very slowly including when filling out her insurance forms and getting up and going to the bathroom. She has 4/5 strength in all extremities and a stable and slow gait. Which of the following is the most likely diagnosis?