Subjective and objective measures of hot flashes

Up to 75% of women in the US report having experienced hot flashes during the menopausal transition. The purpose of this review is to describe the physiology of hot flashes, and the ways in which hot flashes have been examined by subjective report and by objective measurement. Hot flashes occur because of an activation of the heat dissipation response, possibly triggered by a hypothalamic mechanism within the context of declining estrogen levels. There is cross‐population variation in the frequency of self‐reported hot flashes, although cross‐study comparisons are problematic because of incompatibilities in study design. Diaries are a good way to collect information on the time and severity of hot flashes, and body diagrams allow researchers to study the pattern of heat and sweating. Hot flashes can be objectively measured by increases in heart rate, finger blood flow, respiratory exchange ratio, skin temperature, and core body temperature. Sternal skin conductance is the method most highly correlated with subjective hot flash report. In a laboratory, concordance between subjective report and sternal skin conductance can approach 100%. Ambulatory monitoring allows for the tracking of hot flashes during a woman's daily routine or sleep; however, concordance is much lower with ambulatory, compared to laboratory, monitoring. The study of hot flashes at menopause provides a model for the study of any experience that can be assessed by both self‐report and biometric measurement. Am. J. Hum. Biol., 25:573‐580, 2013. © 2013 Wiley Periodicals, Inc.     

Improving the performance of physiologic hot flash measures with support vector machines

Hot flashes are experienced by over 70% of menopausal women. Criteria to classify hot flashes from physiologic signals show variable performance. The primary aim was to compare conventional criteria to Support Vector Machines (SVMs), an advanced machine learning method, to classify hot flashes from sternal skin conductance. Thirty women with ≥4 hot flashes/day underwent laboratory hot flash testing with skin conductance measurement. Hot flashes were quantified with conventional (≥2 μmho, 30 s) and SVM methods. Conventional methods had poor sensitivity (sensitivity=0.41, specificity=1, positive predictive value (PPV)=0.94, negative predictive value (NPV)=0.85) in classifying hot flashes, with poorest performance among women with high body mass index or anxiety. SVM models showed improved performance (sensitivity=0.89, specificity=0.96, PPV=0.85, NPV=0.96). SVM may improve the performance of skin conductance measures of hot flashes.     

Association between hot flashes, sleep complaints, and psychological functioning among healthy menopausal women

Self-report data suggest that sleep hot flashes among menopausal women are associated with sleep problems and in turn impaired psychological functioning. However, few studies have examined these relations with physiologic hot flash measures. A total of 41 perimenopausal and postmenopausal women with daily hot flashes underwent nighttime sternal skin conductance monitoring to quantify hot flashes. Participants completed sleep diaries; the Sleep-Wake Experience List (van Diest, 1990); and depression, anxiety, and daily stress measures. Participants experienced a median of 2 physiologically monitored and 1 reported sleep hot flash nightly. Although sleep complaints were significantly and positively associated with psychological functioning, neither sleep complaints nor psychological functioning was significantly related to frequency of physiologically monitored sleep hot flashes. Conversely, results indicate an association between reported sleep hot flashes and acute sleep problems. The frequency of physiologically monitored sleep hot flashes, as opposed to reported sleep hot flashes, may be independent of problems with sleep and mood among menopausal women.     

Hot flashes are associated with increased ambulatory systolic blood pressure

OBJECTIVE: To determine the association between ambulatory blood pressure (BP) and hot flash experience. DESIGN: The participants in the study were 154 women (mean age=46 years, range=18-65 years), who were evaluated as part of a cross-sectional study on ethnicity, socioeconomic status, and diurnal BP patterns. Participants could be either normotensive or mildly hypertensive. Participants wore an ambulatory BP monitor for 24 hours and recorded their awake and sleep times. Hot flashes were assessed using an everyday complaint questionnaire that embeds symptoms associated with menopause into a list of everyday complaints. RESULTS: Thirty-three percent of participants reported having had hot flashes during the 2 weeks before they completed the questionnaire. Compared with women who did not report hot flashes, mean awake and sleep systolic BP values were significantly higher (P<0.004 and P=0.007, respectively) in women who reported having had hot flashes. Hot flashes continued to independently predict average awake and sleep systolic BP (both P=0.03) after controlling for age, race/ethnicity, body mass index, and menopausal status. Hot flashes were not associated with diastolic BP or nocturnal dipping of BP. CONCLUSIONS: Hot flashes are associated with increased awake and sleep systolic BP independent of menopausal status. Further investigation is warranted to elucidate the mechanisms by which hot flashes are associated with BP.     

Do menopausal hot flashes have any significant effects on arterial blood gas measurements?

Objectives: To evaluate the effects of menopausal hot flashes on arterial blood gas measurements. Methods: Twelve postmenopausal women with frequent hot flashes were enrolled in this study. Blood samples from femoral artery were collected before and during menopausal hot flashes in each subject, and all blood samples were analyzed for pH, pCO₂, pO₂, HCO₃ standard, total CO₂, and base excess. Arterial blood gas parameters before and during menopausal hot flashes were compared statistically. Results: pH measurements decreased significantly during hot flashes (P<0.05); although the difference was found to be statistically significant, the amount of decrease and the range in which the change took place led us to conclude that this change was clinically insignificant. Other parameters did not show any statistically significant differences between the preflash and flash measurements. Conclusions: Our results indicate that menopausal hot flashes do not have any clinically significant effects on arterial blood gas measurements.     

Support Vector Machines to improve physiologic hot flash measures: application to the ambulatory setting

Most midlife women have hot flashes. The conventional criterion (≥2 μmho rise/30 s) for classifying hot flashes physiologically has shown poor performance. We improved this performance in the laboratory with Support Vector Machines (SVMs), a pattern classification method. We aimed to compare conventional to SVM methods to classify hot flashes in the ambulatory setting. Thirty-one women with hot flashes underwent 24 h of ambulatory sternal skin conductance monitoring. Hot flashes were quantified with conventional (≥2 μmho/30 s) and SVM methods. Conventional methods had low sensitivity (sensitivity=.57, specificity=.98, positive predictive value (PPV)=.91, negative predictive value (NPV)=.90, F1=.60), with performance lower with higher body mass index (BMI). SVMs improved this performance (sensitivity=.87, specificity=.97, PPV=.90, NPV=.96, F1=.88) and reduced BMI variation. SVMs can improve ambulatory physiologic hot flash measures.     

Feasibility and psychometrics of an ambulatory hot flash monitoring device.

OBJECTIVE: To assess the feasibility and psychometric properties of a lightweight, automated, ambulatory sternal skin conductance monitor to measure frequency of hot flashes (HFs) among breast cancer survivors (BCSs). DESIGN: A total of 19 postmenopausal BCSs and 5 premenopausal healthy comparison women participated by wearing the monitor for 24 h during their normal daily activities, including sleep. HFs were assessed using subjective (diaries, event markers) and objective (skin conductance) methods. RESULTS: Problems with subjective reporting of HFs were reported by 35% of BCSs. Technological problems and discomfort related to wearing the monitor were minimal. A total of 243 HFs were recorded using the skin conductance monitor by 17 BCSs and 5 premenopausal women (BCS group M = 13.4; range, 1-30). Subjective reporting of HFs was associated with a 31-33% false-positive rate. Skin conductance monitoring during waking hours was associated with a 30% false-negative rate. CONCLUSIONS: The monitor is a feasible method for objectively assessing HFs in BCSs. Data support continued use of sternal skin conductance as an objective measure of HF frequency. This technology should prove useful as an objective measure of HFs in future intervention research aimed at alleviating the symptom and improving quality of life among BCSs.     

Measurement of hot flashes by sternal skin conductance and subjective hot flash report in Puebla,Mexico

OBJECTIVE: To measure hot flashes by sternal skin conductance in an urban Mexican population and to determine variables associated with hot flash reporting and measurement. DESIGN: From June 1999 to August 2000, 67 perimenopausal women aged 40 to 65 years participated in interviews, anthropometric measures, and a 2-h recording of sternal skin conductance. Changes in sweating were used to demonstrate the presence/absence of a hot flash. During the test, women were asked to report if they experienced a hot flash. RESULTS: During the study period, 10 women reported and demonstrated every hot flash, 24 women never reported or demonstrated a hot flash, 7 demonstrated hot flashes but did not report any of them, 7 reported hot flashes but did not demonstrate any of them, and 19 showed a mixture of responses. Women who demonstrated hot flashes by sternal skin conductance were measured in a warmer room, had more years of education, consumed more eggs as a child, recalled a heavier weight at age 18, and had a lower body mass index at interview compared with women who did not demonstrate hot flashes by sternal skin conductance. Women who subjectively reported hot flashes were measured in a warmer room, were more likely to be postmenopausal, reported more frequent consumption of coffee, and spent fewer months breast-feeding their last child compared with women who did not report the experience of hot flashes during the testing period. CONCLUSION: Room temperature explained part of the variation between women who did and did not demonstrate hot flashes via sternal skin conductance, between women who did and did not report the experience of hot flashes, and between women who did and did not demonstrate concordance in objective and subjective measures. In addition to room temperature, coffee intake, months spent breast-feeding the last child, and recalled weight at age 18 were important variables predicting hot flash experience.     

A pilot study of a Hatha yoga treatment for menopausal symptoms

OBJECTIVE: To assess the feasibility and efficacy of a yoga treatment for menopausal symptoms. Both physiologic and self-reported measures of hot flashes were included. METHODS: A prospective within-group pilot study was conducted. Participants were 12 peri- and post-menopausal women experiencing at least 4 menopausal hot flashes per day, at least 4 days per week. Assessments were administered before and after completion of a 10-week yoga program. Pre- and post-treatment measures included: Severity of questionnaire-rated menopausal symptoms (Wiklund Symptom Check List), frequency, duration, and severity of hot flashes (24-h ambulatory skin-conductance monitoring; hot-flash diary), interference of hot flashes with daily life (Hot Flash Related Daily Interference Scale), and subjective sleep quality (Pittsburgh Sleep Quality Index). Yoga classes included breathing techniques, postures, and relaxation poses designed specifically for menopausal symptoms. Participants were asked to practice at home 15 min each day in addition to weekly classes. RESULTS: Eleven women completed the study and attended a mean of 7.45 (S.D. 1.63) classes. Significant pre- to post-treatment improvements were found for severity of questionnaire-rated total menopausal symptoms, hot-flash daily interference; and sleep efficiency, disturbances, and quality. Neither 24-h monitoring nor accompanying diaries yielded significant changes in hot flashes. CONCLUSIONS: The yoga treatment and study procedures were feasible for midlife women. Improvement in symptom perceptions and well being warrant further study of yoga for menopausal symptoms, with a larger number of women and including a control group.     

Effects of REM sleep and ambient temperature on hot flash-induced sleep disturbance

OBJECTIVE: To determine whether hot flashes produce sleep disturbance in postmenopausal women. DESIGN: This study was performed in a university medical center laboratory with 18 postmenopausal women with hot flashes, six with no hot flashes, and 12 cycling women, all healthy and medication free. Polysomnography, skin and rectal temperatures, and skin conductance to detect hot flashes were recorded for four nights. Nights 2, 3, and 4 were run at 30 degrees C, 23 degrees C, and 18 degrees C in randomized order. RESULTS: During the first half of the night, the women with hot flashes had significantly more arousals and awakenings than the other two groups and the 18 degrees C ambient temperature significantly reduced the number of hot flashes, from 2.2 +/- 0.4 to 1.5 +/- 0.4. These effects did not occur in the second half of the night. In the first half of the night, most hot flashes preceded arousals and awakenings. In the second half, this pattern was reversed. CONCLUSIONS: In the second half of the night, rapid eye movement sleep suppresses hot flashes and associated arousals and awakenings. This may explain previous discrepancies between self-reported and laboratory-reported data in postmenopausal women with hot flashes.     

Variation in sweating patterns: implications for studies of hot flashes through skin conductance

OBJECTIVE: The literature of sweat physiology and population variation in response to heat stress suggests that variation in sweating patterns may affect the measurement of hot flashes. This study examined variation in sweating patterns in Puebla, Mexico, and Amherst, MA, and compared the levels of concordance between subjective and objective measures of hot flashes. DESIGN: Thirteen women in Puebla, Mexico, and 15 women in Amherst, MA, aged 45 to 61, completed surveys, body diagrams of heat flow during a hot flash, anthropometric measures, and the measurement of hot flashes through skin conductance monitoring. Hot flashes were measured through sternal (Mexico and Massachusetts) and nuchal (Mexico only) skin conductance. RESULTS: Mexican women were significantly more likely to describe the heat of hot flashes on the back of their neck (100% vs 40%) and on their arms and/or hands (85% vs 40%) compared with women in Massachusetts. Hot flashes in the midback were associated with concordance between nuchal, but not sternal, measures of skin conductance and subjective report in Mexico. In comparing average scores for concordance between subjective and sternal measures of hot flashes, there was a higher mean score for true positives in Mexico (61% vs 29%, P=0.06) and a significantly higher mean score for false-negative measures in Massachusetts (57% vs 21%, P=0.04). CONCLUSIONS: Variation in rates of concordance between subjective and objective measures were not adequately explained by sweating patterns. Future studies should consider population variation in acclimatization and assess variation in the amount of sweat produced during a hot flash.     

Ambulatory blood pressure and heart rate in relation to hot flash experience among women of menopausal age

OBJECTIVE: The purpose of this study was to evaluate whether ambulatory blood pressure and heart rate varied with hot flash experience among women of menopausal age. SUBJECTS AND METHODS: A total of 1149 ambulatory blood pressure and heart rate measurements from 20 women aged 44-55 were examined. Women were categorized by hot flash experience as (1) having had hot flashes during the study period (Symptomatic during Study; n = 5; 302 measurements), (2) having a past history of hot flashes, but no hot flashes during the study period (Historically Symptomatic; n = 7; 385 measurements), and (3) never having had a hot flash (Asymptomatic; n = 8; 462 measurements). Using repeated measures, nested ANOVA models that also adjusted for posture, the variation in blood pressure and heart rate associated with hot flash experience over the whole day and by location of measurement (microenvironment) was evaluated. RESULTS: The results show that, overall, systolic pressure did not differ among the hot flash experience groups although the Symptomatic during Study group had higher pressures at work than the other two groups (p<0.01), and tended to have higher pressures during sleep (p<0.08). The sleep diastolic pressure of the Asymptomatic group was significantly lower than that of the women who had hot flashes on the study day (p<0.01), but women who had a past history of hot flashes had slightly lower diastolic pressure (p<0.01) than those in the other two groups overall. Heart rates of the Asymptomatic group, however, were significantly lower (4-6 b.p.m.; p<0.001) in each microenvironment and over the whole day than both groups who had hot flash experience. CONCLUSIONS: These data suggest first that there may be a relationship between the experience of hot flashes and accelerated heart rate, and second that women who do not experience hot flashes may have lower sleep blood pressures than women who do.     

Influence of the menopausal transition on polysomnographic sleep characteristics: a longitudinal analysis

Study ObjectivesTo evaluate how change in menopausal status related to spectral analysis and polysomnographic measures of sleep characteristics.MethodsThe Study of Women’s Health Across the Nation (SWAN) Ancillary Sleep Study evaluated sleep characteristics of 159 women who were initially pre- or early perimenopausal and repeated the assessment about 3½ years later when 38 were pre- or early perimenopausal, 31 late perimenopausal, and 90 postmenopausal. Participants underwent in-home ambulatory polysomnography for two to three nights. Average EEG power in the delta and beta frequency bands was calculated during NREM and REM sleep, and sleep duration, wake after sleep onset (WASO), and apnea hypopnea index (AHI) were based on visually-scored sleep.ResultsThe women who transitioned to postmenopause had increased beta NREM EEG power at the second assessment, compared to women who remained pre-or early premenopausal; no other sleep measures varied by change in menopausal status. In multivariate models the associations remained; statistical controls for self-reported hot flashes did not explain findings. In secondary analysis, NREM beta power at the second assessment was greater among women who transitioned into the postmenopause after adjustments for initial NREM beta power.ConclusionsSleep duration and WASO did not vary by menopause transition group across assessments. Consistent with prior cross-sectional analysis, elevated beta EEG power in NREM sleep was apparent among women who transitioned to postmenopause, suggesting that independent of self-reported hot flashes, the menopausal transition is associated with physiological hyperarousal during sleep.     

Patterns of occurrence and concordance between subjective and objective hot flashes among Muslim and Hindu women in Sylhet,Bangladesh

This study examined the pattern of occurrence and the rate of concordance between objective hot flashes measured by sternal skin conductance and the subjective experience of “gorom vap laga” (feeling steaming hot) among Muslim and Hindu women living in Sylhet, Bangladesh. Participants were aged 40–55, not pregnant or lactating, not using hormone therapy, and with no history of hysterectomy. Thirty women wore an ambulatory hot flash monitor for 8 h on average, from mid‐morning to early evening. True positive, false negative, and false positive measures of hot flashes were examined in relation to demographic, reproductive, and lifestyle variables. On body diagrams, women were most likely to indicate hot flashes on the top of their head (64%) and upper chest (68%). The greatest number of objective hot flashes occurred during the hour of 17:00, perhaps due to the heat of the day, and the clothing and activity associated with prayer. Muslim participants demonstrated more objective hot flashes per woman than Hindu participants (1.5 vs. 0.1, P < 0.05), and Muslims had more false positive measures (86%) compared with Hindu participants (0%, P = 0.06). Among all women who reported subjective hot flashes (n = 19), the proportion of true positive scores was 19%. Overall, the frequency of objective hot flashes was low compared with reports from studies in the United States. The pattern of sweating assessed by body diagrams was not associated with variation in hot flash experience. Am. J. Hum. Biol., 2008. © 2008 Wiley‐Liss, Inc.     

The role of anxiety and hormonal changes in menopausal hot flashes

OBJECTIVE: To estimate the association of anxiety with menopausal hot flashes in the early transition to menopause. DESIGN: A randomly identified, population-based cohort of midlife women followed up for 6 years to assess reproductive hormones and other physical, emotional, and behavioral factors. At enrollment, the women were premenopausal, aged 35 to 47 years, and had regular menstrual cycles in the normal range. Enrollment was stratified to obtain equal numbers of African American (n = 219) and white (n = 217) women. RESULTS: At the 6-year endpoint, 32% of the women were in the early transition stage and 20% reached the late menopausal transition or were postmenopausal. Reports of hot flashes increased with the transition stages, which were determined by bleeding patterns. At endpoint, hot flashes were reported by 37% of the premenopausal women, 48% of those in the early transition, 63% of women in the late transition, and 79% of the postmenopausal women. Anxiety scores were significantly associated with the occurrence of hot flashes and were also significantly associated with the severity and frequency of hot flashes (each outcome at P < 0.001). Compared with women in the normal anxiety range, women with moderate anxiety were nearly three times more likely to report hot flashes and women with high anxiety were nearly five times more likely to report hot flashes. Anxiety remained strongly associated with hot flashes after adjusting for menopause stage, depressive symptoms, smoking, body mass index, estradiol, race, age, and time. In a predictive model, anxiety levels at the previous assessment period and the change in anxiety from the previous assessment period significantly predicted hot flashes (P < 0.001). CONCLUSIONS: Anxiety is strongly associated with menopausal hot flashes after adjusting for other variables including menopause stage, smoking, and estradiol levels. Anxiety preceded hot flashes in this cohort. Additional studies are needed to examine the duration of menopausal hot flashes and to determine whether treatments that target anxiety effectively reduce menopausal hot flashes.     

Validation of sternal skin conductance for detection of hot flashes in prostate cancer survivors

The gold standard for objectively measuring hot flashes in women is an increased sternal skin conductance level (SCL), but validation studies in prostate cancer patients are lacking. In the laboratory, an SCL increase of > or = 1.78 micro-mho in 45 s had a sensitivity of 68% and a positive predictive value of 100% in detecting self-reported hot flashes among prostate cancer patients. Outside the laboratory, 71% of the objective markers of hot flashes were accompanied by a subjective report of a hot flash, and 65% of subjective reports occurred in the absence of an objective criterion. This study demonstrates that sternal skin conductance can be used to detect hot flashes in men in a manner analogous to its utilization among women. Such use would improve outcome analysis of treatment studies.     

Measurement of menopausal hot flushes: validation and cross-validation

Specificity and sensitivity of two physiological markers for hot flushes were investigated. One marker, proposed by Freedman, is an increase of sternal skin conductance, the second marker, proposed by Swartzman, is a physiological profile which consists of skin conductance changes in combination with circulation changes. In our laboratory 20 menopausal women, 15 with frequent hot flushes and 5 without hot flushes, and 5 women with regular menstrual cycles were continuously monitored for 2.5 h on subjective hot flush experience, sternal and palmar skin conductance, dorsal and palmar finger temperature and pulse blood volume. Increase in sternal skin conductance proved to be very specific in contrast to Swartzman's physiological profile, although it was less sensitive. Receiver operating characteristics revealed that an increase combined with a preceding decrease in sternal skin conductance as most specific for, and most sensitive to, subjectively reported hot flushes. This was confirmed by a cross-validation with 34 ‘flushing’ menopausal women.     

更年期潮热的单胺类神经递质学说

潮热是更年期女性最常见的症状,并且其症状与心血管疾病的发生密切相关,严重影响着更年期女性的身心健康,因此,避免和减轻更年期潮热的发生已经成为当今倍受关注的课题。目前,普遍认为潮热是由下丘脑体温调节中枢功能紊乱所致,但其确切的发病机制尚未阐明。最近的研究相继表明,更年期潮热是雌激素与多种神经递质交互作用的结果,其中单胺类神经递质去甲肾上腺素、5 羟色胺和多巴胺等起到了核心作用,现将其综述如下。     

Ambulatory blood pressure and heart rate in relation to hot flash experience among women of menopausal age

Objective: The purpose of this study was to evaluate whether ambulatory blood pressure and heart rate varied with hot flash experience among women of menopausal age.

Subjects and methods: A total of 1149 ambulatory blood pressure and heart rate measurements from 20 women aged 44–55 were examined. Women were categorized by hot flash experience as (1) having had hot flashes during the study period (Symptomatic during Study; n = 5; 302 measurements), (2) having a past history of hot flashes, but no hot flashes during the study period (Historically Symptomatic; n = 7; 385 measurements), and (3) never having had a hot flash (Asymptomatic; n = 8; 462 measurements). Using repeated measures, nested ANOVA models that also adjusted for posture, the variation in blood pressure and heart rate associated with hot flash experience over the whole day and by location of measurement (microenvironment) was evaluated.

Results: The results show that, overall, systolic pressure did not differ among the hot flash experience groups although the Symptomatic during Study group had higher pressures at work than the other two groups (?p<0.01), and tended to have higher pressures during sleep (?p<0.08). The sleep diastolic pressure of the Asymptomatic group was significantly lower than that of the women who had hot flashes on the study day (?p<0.01), but women who had a past history of hot flashes had slightly lower diastolic pressure (?p<0.01) than those in the other two groups overall. Heart rates of the Asymptomatic group, however, were significantly lower (4–6?b.p.m.; p<0.001) in each microenvironment and over the whole day than both groups who had hot flash experience.

Conclusions: These data suggest first that there may be a relationship between the experience of hot flashes and accelerated heart rate, and second that women who do not experience hot flashes may have lower sleep blood pressures than women who do.