Original Research

Prevalence of night sweats in primary care patients

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An OKPRN and TAFP-Net collaborative study




OBJECTIVE: To estimate the prevalence and factors associated with night sweats among adult primary care patients.

STUDY DESIGN: This was a cross-sectional study.

POPULATION: Adult patients in 2 primary care practice-based research networks (PBRNs) during 1 week in the summer and 1 week in the winter in the years 2000 and 2001.

OUTCOMES MEASURES: We measured the prevalence of pure night sweats and night and day sweats in all patients and subgroups defined by age and sex, clinical variables associated with night sweats, and the frequency, severity, and rate of reporting.

RESULTS: Of the 2267 patients who participated, 41% reported experiencing night sweats within the last month, including 23% with pure night sweats and an additional 18% with day and night sweats. The prevalence of night sweats in both men and women was highest in the group aged 41 years to 55 years. In multivariate analyses, factors associated with pure night sweats in women were hot flashes and panic attacks; in men, sleep problems. Variables associated with night and day sweats in women were increased weight, hot flashes, sleep disturbances, and use of antihistamines, selective serotonin reuptake inhibitors (SSRIs), and other (non-SSRI, non-tricyclic) antidepressants; in men, increased weight, hot flashes, and greater alcohol use. A majority of patients had not reported their night sweats to their physicians, even when frequent and severe.

CONCLUSIONS: Night sweats are common and under-reported. Pure night sweats and night and day sweats may have different causes. With regard to the etiologies of pure night sweats, panic attacks and sleep disorders need further investigation.

  • Night sweats are a common experience for primary care patients, but they are frequently not reported to their physicians.
  • There appear to be 2 somewhat distinct patterns of night sweats: pure night sweats and night and day sweats.
  • A history of night sweats should prompt questions about menopause, panic attacks, sleep problems, and certain medications.

Night sweats have been attributed to tuberculosis, other acute and chronic febrile illnesses, menopause, pregnancy, hyperthyroidism, nocturnal hypoglycemia, other endocrine problems, neurologic diseases, sleep disorders (eg, sleep apnea and nightmares), malignancies, autoimmune diseases, coronary artery spasm, congestive heart failure, gastroesophageal reflux disease, psychiatric disorders, and certain medications. In 36 medical and surgical textbooks, night sweats were always discussed within sections covering specific diseases and never as a separate topic. References to the primary literature were never provided. We also searched Micromedix, a comprehensive source of information on medications, using “sweating” and “diaphoresis” as search terms.1 Table W1 contains a comprehensive list of proposed causes of night sweats identified in our searches and accompanying references.

Only 2 epidemiologic studies of night sweats were found in the English language literature. Lea and Aber2 interviewed 174 patients randomly selected from the inpatient units of a university hospital and found that 33% of nonobstetric patients and 60% of obstetric patients reported having had night sweats during the previous 3 months. Twenty-six percent of those with night sweats reported that their nighttime sweating was severe enough to require bathing and changing of bed linens. Reynolds,3 a gastroenterologist, queried 200 consecutive patients seen in his outpatient practice and found that 40% remembered experiencing night sweats at least once during the previous year. A total of 12% reported at least weekly night sweats. A review of the records of 750 patients at the Geriatric Continuity Clinic at the University of Oklahoma Family Medicine Center revealed that 10% reported having experienced night sweats during the previous month, when the question was asked as part of a standard review of systems questionnaire (J.W.M., unpublished data, 1999).

Our study was conducted in an effort to estimate the prevalence of night sweats in adult patients seen in primary care office settings, and to explore the associations of this symptom with demographic factors, physical characteristics, medical problems, and medications. We also sought to determine how distressing this symptom is to those who have it and to their sleep partners, whether patients are likely to report the symptom to their physicians, and what patients and their physicians think causes night sweats in individual cases.


Physician members of the Oklahoma Physicians Resource/Research Network (OKPRN) and the Texas Academy of Family Physicians Research Network (TAFP-Net) enrolled consecutive patients 18 years and older seen in their clinics during a 1-week period in the summer and a second 1-week period in the winter in the years 2000 and 2001. Patients who agreed to participate signed a consent form and then helped the nurse and physician complete a brief questionnaire on a preaddressed, stamped data collection card. For those who declined to participate, a card was generated containing the physician’s code number and the patient’s age and sex. Questions elicited demographic information; information about a selected set of medical conditions; medications, vitamins, herbs, and alcohol used regularly; and information about recent experiences with night sweats. Participating physicians were asked to check the questionnaires for accuracy and to record their opinions regarding the cause of the patients’ night sweats when they reported having had them. A laminated card with definitions of terms was provided to each physician.


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