Prevalence of night sweats in primary care patients: an OKPRN and TAFP-Net collaborative study - Original Research - Statistical Data Included

Journal of Family Practice, May, 2002 by James W. Mold, Migi K. Mathew, Shuaib Belgore, Mark DeHaven

Suspected causes

In cases where patients reported night sweats, only 19% of the patients and 18% of their physicians recorded opinions regarding causation. The suspected causes listed by patients and physicians were similar. Both groups listed menopause most frequently (48% and 44%, respectively). Other etiologies proposed were stress (12% and 8%) and medications (9% and 10%). Physicians listed diabetes as a possible cause in 11% of cases while only 4% of patients listed it. Other suspected causes included obesity, pregnancy, gastroesophageal reflux disease, sleep discomforts, and ambient temperature.

DISCUSSION

As far as we know, this is the first systematic study of night sweats in a primary care population. It is exploratory in nature, and, because of its cross-sectional design, no firm conclusions can be drawn about causation.

Both pure night sweats and night and day sweats are extremely common, with a peak prevalence in men and women 41 to 55 years of age. In contrast to pure night sweats, night and day sweats are experienced infrequently by patients 70 years and older. The factors associated with pure night sweats are somewhat different than those associated with night and day sweats, suggesting different, though probably overlapping, sets of causes. The different associations seen for men and women, and for older and younger patients, are also noteworthy. Patients often fail to report night sweats to their primary care physician, even when frequent and severe, associated with sleep disturbances, or bothersome to others.

Because of the sampling method (ie, consecutive patients rather than a random sample of active patients), the prevalence estimates reflect the frequency at which physicians can expect to encounter patients with this symptom, rather than the prevalence of night sweats among active patients. Since patients with more symptoms probably see physicians more often, we assume we have overestimated the true prevalence of night sweats in the larger population. Participating physicians were also not selected randomly. It is impossible to know how this may have affected our results.

We were surprised that so few of our independent variables were associated with pure night sweats: only panic attacks (all patients), sleep disorders (men and older patients), and hot flashes (women). Factors not associated with pure night sweats included obesity; diabetes, insulin, or oral hypoglycemic agents; acute or chronic infections; gastroesophageal reflux disease; or thyroid medications. Pure night sweats were also not specifically associated with estrogen and progesterone, although they were associated with hot flashes. There was also no association of pure night sweats and alcohol consumption.

The fact that physicians and their patients could only speculate on a cause for night sweats in 1 out of 5 cases suggests a lack of familiarity with the multitude of suspected causes, a failure to detect certain common causes (eg, sleep disorders and panic attacks), or, most likely, that many common causes of night sweats have yet to be elucidated. If the last is correct, it may be an example of the bias in the primary and secondary clinical literature that occurs when clinical research is carried out primarily in the subspecialty clinics of academic medical centers. (4-7) Our findings speak to the need for greater support for primary care practice-based research. (8,9)