Orthostatic Hypotension: This condition is characterized by a sudden drop in blood pressure when standing up, leading to dizziness. The patient's age and complaint of dizziness upon standing from a bent position make this a likely diagnosis. High LDL levels may contribute to vascular stiffness, potentially exacerbating orthostatic changes.

Hypertension: Although high LDL is mentioned, hypertension is a common comorbidity and could contribute to dizziness through various mechanisms, including cardiac effects or even orthostatic hypotension in the context of autonomic dysfunction.
Cardiac Conditions (e.g., Aortic Stenosis, Heart Failure): These conditions can lead to reduced cardiac output, which might result in dizziness upon exertion or postural changes. The patient's age and high LDL increase the likelihood of underlying cardiac disease.
Anemia: Could be a contributing factor to dizziness, especially if the patient has a condition leading to anemia, such as gastrointestinal bleeding from aspirin use (common in patients with high LDL for cardiovascular protection).

Cardiac Arrhythmias (e.g., Atrial Fibrillation): These can cause dizziness due to irregular heartbeats leading to reduced cardiac output. Given the patient's age and potential for underlying heart disease, missing this diagnosis could be critical.
Subclavian Steal Syndrome: A rare condition but one that could cause dizziness upon exertion, due to reversal of blood flow in the vertebral artery, potentially leading to vertebral-basilar insufficiency.
Pulmonary Embolism: Although less likely, pulmonary embolism can cause dizziness among other symptoms and is a diagnosis that cannot be missed due to its high mortality rate if untreated.

Vasovagal Syncope: While more common in younger individuals, it could still occur in a 64-year-old, especially if triggered by specific maneuvers like bending down and standing up quickly.
Multiple System Atrophy (MSA): A neurodegenerative disorder that can cause autonomic dysfunction leading to orthostatic hypotension. It's rare but should be considered in the differential diagnosis of persistent and unexplained orthostatic hypotension.
Pheochromocytoma: A rare tumor of the adrenal gland that can cause episodic hypertension and orthostatic hypotension, leading to dizziness.