What causes excessive sweating at night and how is it treated?

Excessive Sweating at Night: Causes and Treatment

Excessive sweating at night (night sweats) is a nonspecific symptom that requires systematic evaluation for underlying medical conditions using the "SCREeN" framework (Sleep disorders, Cardiovascular disease, Renal disease, Endocrine disorders, Neurological conditions), with treatment directed at the identified cause rather than the sweating itself. 1

Primary Causes to Evaluate

Sleep Disorders

Night sweats are strongly associated with multiple sleep disorders that require specific screening 2:

• Obstructive sleep apnea (OSA): Ask if the patient gasps or stops breathing at night, wakes unrefreshed, or falls asleep during the day 1
• Insomnia and other sleep disorders: Determine if sleep problems exist beyond the sweating itself 1
• Restless legs syndrome/periodic limb movements: These conditions cause sympathetic overactivity leading to nocturnal hyperhidrosis 2
• Narcolepsy: Associated with hyperhidrosis due to orexin deficiency and sympathetic dysfunction 2

Cardiovascular Disease

• Heart failure: Screen for ankle swelling and shortness of breath on exertion 1
• Hypertension: Review blood pressure status 1
• Perform ECG and brain natriuretic peptide if heart failure is suspected 1

Endocrine Disorders

• Thyroid dysfunction: Both overactive and profoundly underactive thyroid can cause night sweats 1
• Diabetes mellitus: Ask about excessive thirst 1
• Menopause/hormonal changes: Inquire about menstrual changes in women of relevant age 1
• Obtain baseline HbA1c, thyroid function tests, and calcium levels 1

Neurological Conditions

• Screen for movement problems, tremor, gait abnormalities, or speech disturbances 1
• Check lying/standing blood pressure for orthostatic hypotension (fall of 20 systolic or 10 diastolic within 1-3 minutes) 1

Medication Review

Critical medications that can cause night sweats 1:

• Antidepressants (especially SSRIs)
• Decongestants
• Stimulants
• Diuretics (timing matters—should be taken in morning)
• Calcium channel blockers
• Anticholinergics causing xerostomia (dry mouth leading to increased fluid intake)

Diagnostic Approach

Initial Evaluation

1. Determine pattern: Generalized versus localized sweating helps distinguish secondary from primary causes 3
2. Assess impact: Evaluate quality of life impairment and daytime function 1
3. Physical examination: Look for peripheral edema, reduced salivation, tremor, gait abnormalities 1

Baseline Investigations

• Blood tests: electrolytes, renal function, thyroid function, calcium, HbA1c 1
• Consider sleep study (overnight oximetry) if OSA suspected using STOP-BANG questionnaire 1
• ECG and echocardiogram if cardiovascular disease suspected 1

Treatment Strategy

Treatment must focus on the underlying medical condition, not the sweating symptom itself. 1

Treat the Underlying Cause

• Sleep disorders: Refer to sleep clinic for CPAP therapy (OSA), treat restless legs syndrome with ferritin supplementation if levels below 75 ng/ml 1
• Cardiovascular disease: Optimize heart failure management, control hypertension 1
• Endocrine disorders: Correct thyroid dysfunction, optimize diabetes control 1
• Medication adjustment: Review timing of diuretics (move to morning), consider alternatives for medications causing xerostomia 1

Symptomatic Management for Primary Hyperhidrosis

If no underlying cause is identified after thorough evaluation 4, 5:

1. First-line: Topical aluminum salts (antiperspirants)—quick and easy but may cause irritation 5
2. Second-line: Topical anticholinergics or iontophoresis—well tolerated but require maintenance 4, 5
3. Third-line: Botulinum toxin A injections—effective but require repeat treatments every 6-8 months 5
4. Adjunctive: Alpha-adrenergic blockers may reduce night sweats in patients taking SSRIs 6

Important Caveats

• Do not assume causation: A diagnosed medical condition does not automatically explain night sweats in an individual patient; successful treatment of the condition should lead to simultaneous reduction in sweating 1
• Life expectancy considerations: In primary care patients, night sweats alone do not appear to reduce life expectancy 6
• Avoid systemic anticholinergics: While they reduce sweating, the doses required cause significant adverse effects that limit effectiveness 5
• Prevalence is high: 10-60% of various patient populations report night sweats, making it a nonspecific symptom 6

When to Refer

• Sleep clinic: Persistent daytime dysfunction despite conservative treatment, confirmed OSA or RBD 1
• Cardiology: Suspected heart failure with positive brain natriuretic peptide 1
• Neurology: New-onset severe symptoms with neurological signs 1
• Endocrinology: Hypercalcemia or suspected diabetes insipidus 1