A 65-year-old woman presents to her primary care physician with what she calls "symptoms of old age," ie, trouble remembering things and being easily confused, increased anxiety, difficulty managing her bills and household functions, and taking a very long time to perform routine tasks. She also reports getting lost twice in her neighborhood recently while walking home from the store, a trip she takes regularly, as well as frustration at increased clumsiness.

The patient's medical history is largely unremarkable. She has both high cholesterol and hypertension, which are well managed with atorvastatin 80 mg/d and losartan 50 mg/d, respectively. There is no family history of neurodegenerative disease or dementia of any kind as well as negative history of transient ischemic attack or cerebrovascular accident.

Physical exam reveals normal vital signs, mild anomic aphasia, and some visuospatial dysfunction. Laboratory tests reveal nothing remarkable with normal values for: complete blood count, cobalamin (B12), alanine aminotransferase and aspartate aminotransferase, and thyroid stimulating hormones. Vitamin D levels are 18 ng/mL, which shows slight deficiency.