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Frequently Asked Questions From Clinical Practice
Arch Fam Med. 1999;8:168-169.
What is the appropriate diagnostic approach for patients who complain of night sweats?
SEARCH STRATEGY
M. Lee Chambliss, MD, MSPH
A MEDLINE search was performed (1966 to present, limited to the English language) on the following keywords: night or nocturnal sweats (text word), and hyperhidrosis or sweating (medical subject heading [MeSH]) + night or nocturnal (text word).
Night sweats are defined as unusual sweating that occurs only or mainly at night. They range from mild, requiring only the removal of blankets or the turning of a pillow, to severe, requiring bathing or a change of clothes or sheets.
Sweating helps regulate body temperature, fluid, and electrolyte balances. Sweat glands are controlled by the sympathetic and cholinergic nervous systems. The amount and distribution of sweating can vary greatly from one person to another. There are no convincing explanations why in some people sweating occurs mainly at night or why night sweats may be associated with certain diseases. Circadian rhythms may play a role, or perhaps sweating is just more noticeable during the night.
The list of differential diagnoses for night sweats is quite long. The causes can be divided into several major categories. Table 1 lists many of the diagnoses that have been associated with night sweats.
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Differential Diagnosis for Night Sweats
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There are very few studies on the epidemiology of night sweats. Lea and Aber1 interviewed 174 randomly sampled patients admitted to the Hershey Medical Center, Hershey, Pa, in 1980. Patients were asked whether they had night sweats in the previous 3 months. Thirty-three percent of nonobstetric patients and 60% of obstetric patients reported night sweats. Twenty-six percent of these patients had sweating severe enough to require bathing and a change of linens. The mean duration of the night sweats was 10.5 months. Night sweats were not significantly associated with underlying diseases. Few patients in this group had been admitted to the hospital for chronic infections or endocrine diseases. Five of the 9 patients with lymphomas or leukemias reported night sweats.
Reynolds,2 a gastroenterologist with a primary care practice, questioned 200 consecutive patients about night sweats. He found that 40% remembered having 1 or more episode of night sweats in the last year. Twelve percent had an episode of night sweats at least once a week. Reynolds classified the causes for the 81 patients who reported night sweats as follows: esophageal reflux, 44%; menopause, 26%; external overheating, 17%; and miscellaneous or unknown, 13%. Sixty-five (80%) of his patients with frequent night sweats responded to antireflux therapy.
DIAGNOSTIC APPROACH
There is very little evidence available to help determine the best diagnostic approach to night sweats. Patient history seems to be by far the most valuable diagnostic tool for evaluating night sweats. Specific areas of inquiry include menopause status, medications, reflux symptoms, and the following red flag items:
Symptoms
Weight loss
Cough and/or sputum production
Exposure to tuberculosis or human immunodeficiency virus
Exertional symptoms such as chest pain or dyspnea
Physical Signs
Fever
Adenopathy
Hypertension that is episodic and difficult to control
Neurological abnormalities
Patients should be asked to record their temperatures to determine if their sweating is associated with pyrexia. If they do have a fever (>38.3°C[>101°F]), a diagnostic workup for fever without source is recommended.
The few medical sources that mention night sweats recommend very different diagnostic laboratory approaches,3-6 ranging from no routine tests without clinical findings that suggest associated disease to many tests including chemistry panels and electrocardiograms. Since night sweats not associated with other problems seem to be quite common, routine laboratory tests are unlikely to be very helpful without findings in the patient's medical history or on physical examination that suggest associated disease. The low pretest probability for serious cases of night sweats will mean most positive routine tests will be false.
Often reassurance and close monitoring for a change in symptoms is all that patients require. If the sweating is very bothersome, therapies aimed at decreasing perspiration maybe tried, including local treatment with aluminum chloride hexahydrate (Drysol; Person & Covey Inc, Glendale, Calif) or other antiperspirants. Some physicians have used systemic medications such as scopolamine or phenoxybenzamine hydrochloride to treat patients; however, no good clinical trials have been conducted in this area, and the adverse effects may be more bothersome than the sweating.6-7
BOTTOM LINE
There is no evidence that we should routinely ask patients screening questions to detect night sweats. If a patient presents with complaints of night sweats, the clinical examination should address the areas indicated previously. If red flag areas are uncovered, then indicated diagnostic workups should be undertaken. If, as is often the case, there are no red flag areas or diagnostic clues, an investigation is not mandatory.
Moses Cone Health System
Department of Family Medicine
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Greensboro, NC 27401-1007
REFERENCES
1. Lea MJ, Aber RC. Descriptive epidemiology of night sweats upon admission to a university hospital. South Med J. 1985;78:1065-1067.
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2. Reynolds WA. Are night sweats a sign of esophageal reflux [letter]? J Clin Gastroenterol. 1989;11:590-591.
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3. Smetana GW. Diagnosis of night sweats. JAMA. 1993;270:2502-2503.
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4. Collins RD. Diaphoresis. In: Algorithmic Diagnosis of Symptoms and Signs: Cost-Effective Approach. New York, NY: Igaku-Shoin Medical Publishers; 1995:133.
5. Phillips DM. Hyperhidrosis. In: Taylor RB, ed. Difficult Diagnosis. Philadelphia, Pa: WB Saunders Co; 1985:252-261.
6. Shellow W. Disturbances of skin hydration: dry skin and excessive sweating. In: Primary Care Medicine. 3rd ed. Philadelphia, Pa: JB Lippincott; 1995:903-906.
7. Manusov EG, Nadeau MT. Hyperhidrosis: a management dilemma. J Fam Pract. 1989;28:412-415.
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