“Night sweats” was defined as “sweating at night even when it isn’t excessively hot in your bedroom.” “Day sweats” was defined as “excessive sweating during the daytime.” “Pure night sweats” was defined as night sweats, but not day sweats, and “night and day sweats” as the combination of the 2. The time interval was specified as “during the last month.”
Completed questionnaires were mailed to the Oklahoma Center for Family Medicine Research for data entry and analysis. The data collection cards used by the Texas network included questions about race/ethnicity and panic attacks that were not included on the Oklahoma cards. Inadvertently, some of the Texas cards did not include the question about daytime sweating.
Statistix7 (Analytical Software, Tallahassee, Fla) was used for all statistical analyses. Medications were assigned to 1 of 47 categories according to their primary pharmacologic effects. Summary statistics were calculated for all participants and for the following subgroups: season (summer and winter), pattern of night sweats (excessive nighttime sweating only or night and day sweats), and age group. We anticipated that the majority of women with menopausal symptoms would be in the 41- to 55-year age group.
The two patterns of night sweats, “pure night sweats” and “night and day sweats,” were analyzed separately, and by sex and age. Logistic regression was used to identify the most significant predictors of night sweats while controlling for other variables. Variables were entered into the logistic models if they had a univariate association with the dependent variable at a P value of less than .05. They were then removed one at a time, in the order of largest to smallest P value, if they had a P value of greater than .01 after controlling for other variables. Conservative P values were chosen because of the large numbers of variables considered, in order to reduce the probability of type 1 errors. When appropriate, 95% confidence intervals were calculated.
Results
Study population
A total of 2267 patients of 31 different physicians participated in this study, including 1888 patients of 24 Oklahoma physicians and 379 patients of 7 Texas physicians. Their mean (standard deviation) age was 50.7 (18.8) years, with a range of 18 to 97 years. Sixty-nine percent were women. A total of 99% of Oklahoma patients and 93% of Texas patients seen during the study weeks agreed to participate in the study. Among Texas participants, 53% were Hispanic whites, 33% were non-Hispanic whites, 13% were African Americans, and 1% were categorized as other. On the basis of prior OKPRN studies, we suspect that approximately 90% of Oklahoma patients were non-Hispanic whites, but exact proportions were not determined for this study.
Prevalence of night sweats
The prevalence of pure night sweats, night and day sweats, and any night sweats are shown in Table 1. While the prevalence of night and day sweats was lower for older patients, severity tended to be greater. Severity and frequency were positively correlated for all categories of night sweats and for all subgroups of patients (overall Spearman coefficient = 0.33; P < .001). Overall, the frequencies of night sweats among those who reported the condition were: almost never, 18%; 1 to 3 nights per month, 38%; 1 to 3 nights per week, 27%; and 4 to 7 nights per week, 16%. Ten percent of both women and men with night sweats said that their night sweats were bothersome to others.
TABLE 1
Percentage of patients with pure night sweats and night and day
| Patient group, by sex and age, in years | Pure night sweats % (95% CI) | Night and day sweats % (95% CI) | Any night sweats % (95% CI) |
|---|---|---|---|
| All patients | 23 (21-24) | 18 (16-20) | 41 (39-43) |
| Men | 22 (19-26) | 12 (9-14) | 34 (30-38) |
| 18-40 | 20 (14-26) | 14 (9-19) | 35 (28-42) |
| 41-55 | 25 (18-32) | 14 (9-19) | 40 (33-47) |
| 56-69 | 24 (16-32) | 12 (6-18) | 38 (30-46) |
| 70+ | 20 (13-27) | 6 (2-10) | 26 (19-33) |
| Women | 23 (21-25) | 21 (19-24) | 44 (42-47) |
| 18-40 | 22 (18-26) | 19 (15-23) | 42 (38-46) |
| 41-55 | 29 (24-34) | 32 (28-37) | 61 (56-66) |
| 56-69 | 22 (18-27) | 23 (18-28) | 43 (37-49) |
| 70+ | 19 (14-24) | 9 (5-13) | 29 (24-34) |
| CI denotes confidence interval. | |||
Frequency of reporting of night sweats
A minority of patients with night sweats (12%) had reported the symptom to their physicians. This was true even for those with severe night sweats (46%). Women younger than 70 years were more likely than men of the same age to have reported their night sweats to their physicians (15% vs. 6%; P < .001). The reverse was true for those 70 years and older (7% vs 13%; P =.08). Older patients with pure night sweats were more likely than younger patients to have reported them. After controlling for other variables, patients who were older (odds ratio [OR] = 1.03 per year of age; P < .001), those with night and day sweats (OR = 1.74; P =.0015), and those who reported that their night sweats bothered others (OR = 2.89; P =.001) were more likely to have reported the symptom to their physicians. Those who had reported their night sweats were also more likely to have hot flashes (OR = 2.98; P < .001) and to take estrogen (OR = 1.72; P =.003).