What diseases and conditions can cause mouth dryness in patients, particularly in older adults or those with a history of head or neck radiation therapy?

Diseases and Conditions That Cause Mouth Dryness

Mouth dryness (xerostomia) is primarily caused by medications with anticholinergic or anti-adrenergic properties, autoimmune diseases (particularly Sjögren's syndrome), head and neck radiation therapy, and systemic diseases including diabetes mellitus—with medications being the single most common culprit, especially in older adults. 1, 2

Autoimmune and Rheumatologic Diseases

• Sjögren's syndrome is the primary autoimmune cause, characterized by lymphocytic infiltration of lacrimal and salivary glands, affecting approximately 0.4% of the population with a 20:1 female-to-male ratio 1
• Sicca syndrome presents with abrupt onset dry mouth, usually without dry eyes, and can occur independently of Sjögren's syndrome 1
• Sicca complex is common in primary biliary cholangitis (PBC), with dry eyes and/or dry mouth frequently seen 1
• Rheumatoid arthritis can cause salivary gland hypofunction 1
• Systemic lupus erythematosus is associated with xerostomia 3
• Sarcoidosis can trigger reduced salivation 4

Radiation-Induced Causes

• Head and neck radiation therapy affecting salivary glands causes radiation-induced dry mouth and painful mucositis 3
• Radiation to the head and neck is a well-established cause of severe, often permanent xerostomia 5, 6, 7
• Orbital radiation can contribute to dry mouth 3

Endocrine and Metabolic Diseases

• Diabetes mellitus is the most common endocrine cause, affecting parasympathetic innervation and causing autonomic dysfunction 8, 1, 5, 4
• Thyroid dysfunction can diminish salivation 5
• Metabolic syndrome is associated with xerostomia in elderly patients 3

Neurological Conditions

• Parkinson's disease causes bradykinesia of swallowing muscles, leading to saliva pooling despite normal or reduced production 8, 1
• Stroke affects 50% of patients with clinically significant dysphagia and subsequent saliva accumulation 8
• Multiple sclerosis causes dysphagia in over one-third of patients, worsening in late stages 8
• ALS (Amyotrophic Lateral Sclerosis) presents with swallowing impairment in 30% at diagnosis, with nearly all patients developing it as disease progresses 8
• Myasthenia gravis manifests with dysphagia in 15% initially, affecting over 50% as illness progresses 8
• Traumatic brain injury causes clinically relevant dysphagia in approximately 60% of cases 8
• Bell's palsy can contribute to dry mouth 3, 1
• Dementia is associated with dysphagia and related oral symptoms 1
• Riley-Day syndrome (familial dysautonomia) affects salivary function 3
• Trigeminal neuralgia and its surgical treatment can cause xerostomia 3

Renal and Cardiovascular Diseases

• Chronic kidney disease causes salivary disorders, including altered salivary composition that may affect flow and consistency 8, 1, 2
• Nephritis can diminish salivation 5
• Heart failure is commonly associated with dry mouth 1

Infectious Diseases

• Hepatitis C can cause chronic viral infection affecting salivary function 3
• HIV is associated with xerostomia 3
• Herpes viruses (Epstein-Barr, cytomegalovirus) have been isolated in myenteric plexuses of patients with visceral neuropathy 8
• Chagas disease (South American trypanosomiasis) causes megaesophagus with bacterial overgrowth and dysphagia 8
• Lyme disease causes reversible dysmotility affecting swallowing 8

Dermatological and Systemic Inflammatory Diseases

• Rosacea is associated with dry mouth 3
• Psoriasis can contribute to xerostomia 3
• Scleroderma affects salivary function 3, 1
• Stevens-Johnson syndrome causes severe dry mouth 3
• Ocular mucous membrane pemphigoid is associated with dry eye and mouth 3

Hematologic and Oncologic Conditions

• Graft-versus-host disease (GVHD) following bone marrow transplant causes severe xerostomia 3
• Lymphoma can be associated with dry mouth 3

Anatomic and Mechanical Causes

• Chronic nasal obstruction from chronic rhinosinusitis, allergic rhinitis, or anatomic abnormalities forces mouth breathing, dramatically worsening dry mouth 2
• Obstructive sleep apnea causes mouth breathing and should be screened for with questions about gasping/stopping breathing at night 2
• Endotracheal intubation can result in dysphagia and oral dryness 1

Age-Related Factors

• Presbyphagia (age-related swallowing changes) causes inefficient clearance, leading to pooling 8
• 16% of independently living persons aged 70-79 and 33% aged 80+ have oropharyngeal dysphagia 8
• 51% of institutionalized elderly are affected by swallowing disorders 8
• Salivary flow rate declines with age, making older adults more susceptible to dry mouth even without other risk factors 1, 2

Critical Clinical Pitfalls

• Distinguish true hypersalivation from apparent hypersalivation: Many neurological conditions cause saliva pooling due to impaired clearance rather than overproduction 8
• Rule out mimicking conditions: Candidiasis, burning mouth syndrome, and dysphagia can present similarly to xerostomia 1, 2
• Measure objective salivary flow: The patient's subjective sensation may not correlate with actual salivary output 1, 2
• Elderly patients face substantially higher risk due to polypharmacy combined with age-related decline in salivary flow 1, 2