What are the causes of orthostatic hypotension in older adults?

Causes of Orthostatic Hypotension in Older Adults

Medications: The Most Common Culprit

Medications are the most frequent cause of orthostatic hypotension in older adults and should be the first consideration in any evaluation. 1

High-Risk Medication Classes:

• Diuretics cause volume depletion and are among the most common culprits in medication-induced orthostatic hypotension 1
• Vasodilators (including nitrates) directly reduce vascular tone, contributing to orthostatic hypotension 1
• Alpha-adrenergic blockers impair vasoconstriction and are particularly problematic in initial orthostatic hypotension 1
• Beta-blockers can worsen orthostatic symptoms 1
• Psychotropic drugs are frequently implicated 1
• Any vasoactive drugs can contribute to classical or delayed orthostatic hypotension 1

Autonomic Nervous System Dysfunction

Primary Autonomic Failure:

• Multiple system atrophy with widespread autonomic degeneration is a primary autonomic failure that can cause orthostatic hypotension 1
• Parkinson's disease with autonomic involvement is a common cause in older adults 1
• Pure autonomic failure affecting peripheral autonomic nerves can lead to orthostatic hypotension 1
• Dementia with Lewy bodies can cause neurogenic orthostatic hypotension 2

Secondary Autonomic Failure:

• Diabetes mellitus causing autonomic neuropathy is a secondary autonomic failure that significantly increases prevalence of orthostatic hypotension in all age groups 1, 3
• Amyloidosis with autonomic nerve infiltration is a secondary autonomic failure that can cause orthostatic hypotension 1
• Spinal cord injuries can result in autonomic dysfunction 2
• Auto-immune autonomic neuropathy and paraneoplastic autonomic neuropathy are less common causes 2

Pathophysiologic Mechanism:

In neurogenic orthostatic hypotension, cardiovascular sympathetic fibers fail to increase total peripheral vascular resistance upon standing, resulting in inadequate vasoconstriction and a blunted heart rate response (usually <10 beats per minute) 1, 4

Volume Depletion and Hypovolemia

• Severe volume depletion causes non-neurogenic orthostatic hypotension with a preserved or enhanced heart rate response 1
• Excessive diuresis is a common cause of volume depletion-related orthostatic hypotension 1
• Dehydration or blood loss can precipitate acute orthostatic hypotension 5

Age-Related Physiologic Changes

Aging itself predisposes to orthostatic hypotension through multiple mechanisms, making it particularly prevalent in older adults. 1

Specific Age-Related Mechanisms:

• Stiffer hearts less responsive to preload changes contribute to orthostatic hypotension in older adults 1
• Impaired compensatory vasoconstrictor reflexes are a key age-related change 1
• Baroreflex dysfunction from age-related changes can lead to orthostatic hypotension 1
• Reduced cerebral autoregulation is an age-related change that can contribute to orthostatic hypotension 1

Epidemiologic Impact:

• Orthostatic hypotension occurred in approximately 7% of men over 70 years in the Honolulu Heart Study and was associated with a 64% increase in age-adjusted mortality 1
• Prevalence ranges from 6% in community-dwelling elderly to 33% in elderly hospital inpatients 1
• Prevalence is 20% in older adults compared to only 5% in middle-aged adults 3

Cardiovascular Causes

• Severe arteriosclerosis causing pseudohypertension can lead to orthostatic hypotension 1
• Decreased cardiac output due to poor ventricular function in heart failure can worsen orthostatic hypotension, though the primary defect remains inadequate peripheral vasoconstriction 1

Clinical Significance and Diagnostic Approach

Key Distinguishing Features:

• Neurogenic orthostatic hypotension shows a blunted heart rate increase (usually <10 beats per minute) due to impaired autonomic control 1, 4
• Non-neurogenic orthostatic hypotension (e.g., hypovolemia) shows preserved or enhanced heart rate increase 1

Common Pitfalls:

• In patients with supine hypertension, a systolic BP drop ≥30 mmHg should be considered diagnostic rather than the standard 20 mmHg threshold 1, 4
• Pseudohypertension in elderly patients with calcified arteries may lead to overtreatment and iatrogenic orthostatic hypotension 4
• Drug-induced autonomic failure is frequently overlooked but is a common and reversible cause 4

Prevalence and Impact:

• Orthostatic hypotension accounts for 20-30% of syncope cases in older adults 1
• It is associated with increased mortality, cardiovascular disease prevalence, and significantly increases fall risk, especially backward falls in elderly patients 1
• Up to a 50% increase in relative risk of all-cause mortality is associated with orthostatic hypotension 3