What causes nocturnal sweating?

Causes of Nocturnal Sweating

Nocturnal sweating results from a diverse array of physiological, pathological, and iatrogenic mechanisms, with the most common causes in primary care being menopause, mood disorders, gastroesophageal reflux disease, hyperthyroidism, obesity, and obstructive sleep apnea—though most patients presenting with this symptom do not have a serious underlying disorder. 1

Primary Physiological Mechanisms

Circadian and Thermoregulatory Factors

• Cortisol nadir during nighttime removes natural anti-inflammatory suppression, creating a pro-inflammatory environment that can trigger sweating 2
• Increased skin temperature and poor barrier function at night lead to increased transepidermal water loss, which the body attempts to regulate through sweating 2
• Circadian rhythm disruption affects multiple physiological systems including inflammatory mediator peaks (IL-2, IL-31) that can indirectly influence autonomic responses 2, 3

Sleep Architecture Disruption

• Obstructive sleep apnea is a major cause of nocturnal sweating, with excessive sweating listed as a common nighttime symptom in both pediatric (1-5% prevalence) and adult populations (6% women, 13% men) 2
• Sleep stage transitions and arousals during lighter N1 and N2 sleep stages can trigger autonomic responses including sweating 4

Common Medical Conditions

Endocrine Disorders

• Menopause is the most frequent hormonal cause, with hot flashes and night sweats affecting a substantial proportion of women 2, 5
• Hyperthyroidism represents another common hormonal etiology 1, 6, 5
• Hypoglycemia should be considered, particularly in diabetic patients 6
• Hypogonadism in aging males is a rarer cause but must be associated with sexual problems and repeatedly low morning testosterone 5

Cardiovascular and Renal

• Congestive heart failure causes nocturnal sweating through fluid redistribution and autonomic dysregulation 2
• Hypertension is associated with night sweats 2
• Chronic kidney disease can manifest with nocturnal sweating 2

Gastrointestinal and Metabolic

• Gastroesophageal reflux disease is commonly associated with night sweats in primary care 1, 6
• Obesity is a significant risk factor, with 60-90% of OSA patients (who commonly have night sweats) presenting with BMI >30 kg/m² 2

Psychiatric and Sleep Disorders

• Mood disorders including anxiety and panic attacks are common causes 1, 5
• Insomnia, restless legs syndrome, and parasomnias can all contribute to nocturnal sweating 2

Serious Underlying Diseases

Infections

• Tuberculosis remains an important diagnostic consideration despite being infrequently found in modern practice 6
• HIV infection should be evaluated in appropriate clinical contexts 1, 6

Malignancies

• Lymphoma is a disease where night sweats are a dominant symptom, though rarely the ultimate diagnosis in primary care 6
• Other malignancies have been suggested but are not well-supported as common causes 7

Autoimmune Conditions

• Autoimmune diseases have been linked to night sweats, though specific mechanisms remain unclear 7

Medication-Induced Causes

Common Culprits

• Antihypertensives (particularly alpha-adrenergic blockers) 6
• Serotonin reuptake inhibitors (SSRIs) can cause night sweats, with alpha-adrenergic blockers potentially reducing this side effect 7
• Antipyretics 6
• Calcium channel blockers, lithium, and NSAIDs 2

Substances of Abuse

• Alcohol and heroin may cause night sweats 6

Dermatologic Causes

Inflammatory Skin Conditions

• Atopic dermatitis (eczema) causes intense nocturnal pruritus with associated sweating, affecting 10-20% of US children, with 60% experiencing sleep disturbance and 83% reporting problems during exacerbations 2
• Inflammatory cytokine expression (IL-2, IL-31) peaks at night, driving the itch-scratch cycle and associated autonomic responses including sweating 2, 3

Clinical Context and Prognosis

Prevalence and Significance

• Prevalence ranges from 10% in older primary care patients to 60% in specific populations (e.g., women on obstetrics inpatient units) 7
• Life expectancy is not reduced in primary care patients reporting night sweats, indicating most cases are benign 7
• The symptom is nonspecific, and many patients experience it without serious underlying pathology 7, 1

Important Caveats

• Most suggested clinical causes lack strong evidence support, making algorithmic evaluation approaches difficult to justify 7
• Patients commonly experience night sweats but rarely discuss them without direct questioning 1
• Presence of night sweats alone does not indicate increased mortality risk 1