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Am Fam Physician. 2020;102(7):427-433

This clinical content conforms to AAFP criteria for CME.

Author disclosure: No relevant financial affiliations.

Night sweats are a nonspecific symptom that patients commonly experience but rarely discuss with their physicians without prompting. Although many life-threatening causes such as malignancies or infections have been described, most patients who report persistent night sweats in the primary care setting do not have a serious underlying disorder. Conditions commonly associated with night sweats include menopause, mood disorders, gastroesophageal reflux disease, hyperthyroidism, and obesity. If a clinical diagnosis is apparent based on the initial history and physical examination, specific treatment for four to eight weeks may be offered. When the history and physical examination do not reveal a specific cause, physicians should proceed with a systematic and cost-conscious strategy that uses readily available laboratory and imaging studies, such as a complete blood count, tuberculosis testing, thyroid-stimulating hormone levels, HIV testing, C-reactive protein level, and chest radiography. Additional tests that could be considered selectively include computed tomography of the chest and/or abdomen, bone marrow biopsy, polysomnography, and/or additional laboratory studies if indicated. If these results are normal, and no additional disorders are suspected, reassurance and continued monitoring are recommended. The presence of night sweats alone does not indicate an increased risk of death.

Night sweats are a common experience, with a prevalence of up to 41% among primary care patients.1 The definition of night sweats varies and generally does not require that the symptom be bothersome to the patient.2 One definition suggested in a 2010 study was “sweating at night even when it is not excessively hot in your bedroom.”3 New evidence from the primary care setting has been published since the last American Family Physician review of this topic.4

WHAT'S NEW ON THIS TOPIC

Night Sweats

A systematic review found that the cross-sectional prevalence of night sweats ranges from 10% to 41% in the primary care setting, with the highest prevalence occurring in patients between 41 and 55 years of age.

In a study of school-aged children in China, 12% reported having weekly night sweats during the past year. When present, night sweats were associated with obstructive sleep apnea, insomnia, anxiety, and respiratory and atopic symptoms.

A cohort study of 1,534 patients older than 65 years found that after seven years, patients who reported having night sweats were not more likely to die or to die earlier than patients who did not report them.

Epidemiology

In one study conducted in the primary care research setting, only 12% of patients who were explicitly asked about night sweats reported the symptom to their physicians.1 A systematic review found that the cross-sectional prevalence of night sweats ranges from 10% to 41% in the primary care setting in older and middle-aged cohorts, respectively, with the highest prevalence occurring between 41 and 55 years of age.1,2 One study of 843 patients older than 65 years estimated an annual incidence of 5% (i.e., 5% of patients reported the onset of night sweats during one year).3 The only study of night sweats in school-aged children was conducted in China and found that 12% had weekly night sweats in the past year; when present, they were associated with obstructive sleep apnea, insomnia, anxiety, and respiratory or atopic symptoms.5

Pathophysiology

Sweating is controlled by a complex method and serves to reduce the body's core temperature when it exceeds a threshold value called the thermoneutral zone.2 Elevation of core temperature can be caused by excessive bedding, clothing, or environmental heating, which could trigger an appropriate physiologic response. In the absence of environmental factors, some potential mechanisms for night sweats have been suggested. The responsiveness of the sweat glands may be influenced by physical conditioning or acute and chronic anxiety states. Menopausal hot flashes may narrow (or lower) the threshold values of the thermoneutral zone, resulting in more frequent sweating.

Sweating may also occur for reasons unrelated to temperature regulation. Medications or conditions that affect the sympathetic nervous system, thermoregulatory center, or sweat glands may affect the frequency of sweating. Another mechanism may be patient hypervigilance. Individual patients may be less tolerant of night sweats, or may be awake because of another medical condition and are therefore more likely to notice sweating.2

Differential Diagnoses

Night sweats have been associated with an extensive list of conditions; however, these have been generated primarily from case reports and series, commonly from specialty referrals or an inpatient setting (Table 12,4,68 ). Although many life-threatening causes such as malignancies or infections have been described, most patients who report persistent night sweats in the primary care setting do not have a serious underlying disorder. After ruling out environmental factors, physicians should consider the following common possibilities: vasomotor symptoms of menopause, panic attacks, depression, posttraumatic stress disorder, obesity/overweight, alcohol and tobacco use, diabetes mellitus, restless legs, hyperthyroidism, and gastroesophageal reflux disease (GERD).911

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