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

Measuring hot flash phenomenonology using ambulatory prospective digital diaries

OBJECTIVE

This study provides the description, protocol, and results from a novel prospective ambulatory digital hot flash phenomenon diary.

METHODS

This study included 152 midlife women with daily hot flashes who completed an ambulatory electronic hot flash diary continuously for the waking hours of three consecutive days. In this diary, women recorded their hot flashes and accompanying characteristics and associations as the hot flashes occurred.

RESULTS

Self-reported hot flash severity on the digital diaries indicated that the majority of hot flashes were rated as mild (41.3%) or moderate (43.7%). Severe (13.1%) and very severe (1.8%) hot flashes were less common. Hot flash bother ratings were rated as mild (43%), or moderate (33.5%), with fewer hot flashes reported bothersome (17.5%) or very bothersome (6%). The majority of hot flashes were reported as occurring on the face (78.9%), neck (74.7%), and chest (61.3%). Of all reported hot flashes, 32% occurred concurrently with prickly skin, 7% with anxiety, and 5% with nausea. A novel finding from the study was that 38% of hot flashes were accompanied by a premonitory aura.

CONCLUSIONS

A prospective electronic digital hot flash diary allows for a more precise quantitation of hot flashes while overcoming many of the limitations of commonly used retrospective questionnaires and paper diaries. Unique insights into the phenomenology, loci, and associated characteristics of hot flashes were obtained using this device. The digital hot flash phenomenology diary is recommended for future ambulatory studies of hot flashes as a prospective measure of the hot flash experience.

Vasomotor symptoms in prostate cancer survivors undergoing androgen deprivation therapy

OBJECTIVE

Hot flushes and night sweats (HFNS) are common but under-researched in prostate cancer survivors undergoing androgen-deprivation therapy (ADT). We aimed to examine subjective reports and physiological measures of HFNS, and the influence of sociodemographic, clinical and psychological factors on HFNS in men undergoing ADT.

METHODS

Sixty-eight men undergoing ADT for prostate cancer attended an assessment interview, completed questionnaires (assessing HFNS frequency and problem-rating, mood, stress, optimism, somatosensory amplification, HFNS beliefs/behaviors) and wore an ambulatory sternal skin conductance (SSC) monitor for 48 h.

RESULTS

The sample had a mean age of 69.76 (standard deviation, SD = 8.04) years, were on average 27.24 (SD = 28.53) months since cancer diagnosis and had been on their current ADT regime for 16 months (range 2-74 months). The men reported frequent (weekly mean 51.04, SD = 33.21) and moderately problematic HFNS. Overall, 294 (20%) of the SSC-defined HFNS were concordant with prospective frequency (event marker), while 63% were under-reported and 17% were over-reported, under-reporting being more common than over-reporting. There were no significant predictors of HFNS frequency (subjective or physiological measures), but psychological variables (HFNS beliefs and behaviors (β = 0.56, p < 0.03), anxiety (β = 0.24, p < 0.01) and somatic amplification (β = 0.76, p < 0.04) were the main predictors of problematic HFNS, i.e. troublesome symptoms.

CONCLUSIONS

These results are consistent with those of studies of women during menopause and breast cancer survivors, i.e. subjective and physiological measures appear to identify different HFNS dimensions. Psychological variables (HFNS beliefs and behaviors, anxiety and somatic amplification) can be targeted, using cognitive behavior therapy, for symptom relief.

A randomised controlled trial of a brief cognitive behavioural intervention for men who have hot flushes following prostate cancer treatment (MANCAN)

OBJECTIVE

Hot flushes and night sweats (HFNS) are experienced by up to 80% of prostate cancer patients undergoing androgen deprivation therapy (ADT). This study evaluates the effects of a guided self-help cognitive behavioural therapy (CBT) intervention on HFNS problem-rating (primary outcome), HFNS frequency, mood and health-related quality of life (secondary outcomes) in patients undergoing ADT.

METHODS

Patients reporting treatment-induced HFNS were randomly assigned to CBT (n = 33) or treatment as usual (TAU) (n = 35), stratified for cancer type. The CBT intervention included a booklet, CD plus telephone contact during a 4-week period. Validated self-report questionnaires were completed at baseline, 6 weeks and 32 weeks after randomisation. The primary outcome was HFNS problem rating (perceived burden of HFNS) at 6 weeks after randomisation. Potential moderators and mediators were examined. Data analysis was conducted on a modified intention-to-treat basis.

RESULTS

Compared with TAU, CBT significantly reduced HFNS problem rating (adjusted mean difference: -1.33, 95% CI -2.07 to -0.58; p = 0.001) and HFNS frequency (-12.12, 95% CI -22.39 to -1.84; p = 0.02) at 6 weeks. Improvements were maintained at 32 weeks, but group differences did not reach significance. There were significant reductions in negative HFNS Beliefs and Behaviours following CBT, but not in mood or quality of life.

CONCLUSIONS

Guided self-help CBT appears to be a safe and effective brief treatment for men who have problematic HFNS following prostate cancer treatments. Further research might test the efficacy of the intervention in a multicentre trial.

The Hot Flush Beliefs and Behaviour Scale for Men (HFBBS-Men) undergoing treatment for prostate cancer

OBJECTIVE

Hot flushes and night sweats (HFNS) are commonly experienced by men receiving treatment for prostate cancer. Cognitive behavioural therapy (CBT) has been found to be an effective treatment for HFNS in women, but cognitions and behavioural reactions to HFNS in men are under-researched. This study describes the development of the HFNS beliefs and behaviour scale for men.

METHODS

HFNS beliefs and behaviour items were generated from a qualitative study, from pilot interviews with men with prostate cancer and HFNS, and from scales used for women. 118 men with prostate cancer, aged above 18, English-speaking, who had minimum of seven HFNS weekly for at least 1 month, completed the initial measure, and measures of HFNS frequency, problem rating, anxiety and depression (HADS). Principal components analyses with orthogonal rotation determined the most coherent solution.

RESULTS

Exploratory factor analysis culminated in a 17-item HFNS beliefs and behaviour scale for men (HFBBS-Men) with three subscales: (1) HFNS social context and sleep, (2) Calm/Acceptance, (3) Humour/Openness. The subscales had reasonable internal consistency (Cronbach alpha 0.56-0.83). Validity was supported, by correlations between subscale 1, HFNS frequency, problem-rating and mood; men with locally advanced cancer more likely to adopt Calm/Acceptance and those with metastatic cancer Humour/Openness.

CONCLUSIONS

Preliminary analysis of the HFBBS-Men suggests that it is a psychometrically sound instrument, grounded in men's experiences. As a measure of cognitive and behavioural reactions to HF/NS, the HFBBS-Men should increase understanding of the mediators of outcomes of psychological interventions, such as CBT.

Are menopausal hot flashes an evolutionary byproduct of postpartum warming?

OBJECTIVE

Hot flashes are commonly associated with menopause, and some researchers have questioned whether the widespread phenomenon may somehow be adaptive. It has been hypothesized that hot flashes were selected to occur during the hypoestrogenic postpartum period as a mechanism to warm infants. The purpose of this study was to test whether postpartum hot flashes are similar to hot flashes associated with menopause and whether postpartum hot flashes are concordant with breast-feeding episodes.

METHODS

Women who gave birth within the past year (n = 20) and a comparison group of women who had not given birth in the past 2 years (n = 14) participated in interviews and anthropometric measures. All wore ambulatory skin conductance monitors for a mean of 6.5 hours during afternoons and early evenings. New mothers also recorded breast-feeding episodes. Objectively measured and subjectively reported hot flashes were compared between groups and in relation to breast-feeding and other variables.

RESULTS

Age of infants ranged from 4 days to 11 months. New mothers were more likely to report feeling warmer than the comparison group (100% vs 7%) but were not significantly more likely to demonstrate hot flashes (35% vs 50%) or to report hot flashes (30% vs 21%) during the study period. Of 75 breast-feeding episodes, only 4% were concurrent with an objective hot flash, and only 9% were concurrent with a subjective hot flash.

CONCLUSIONS

This study does not support the hypothesis that menopausal-like hot flashes evolved to warm infants during the postpartum period.

Menopausal hot flashes: mechanisms, endocrinology, treatment

Hot flashes (HFs) are a rapid and exaggerated heat dissipation response, consisting of profuse sweating, peripheral vasodilation, and feelings of intense, internal heat. They are triggered by small elevations in core body temperature (Tc) acting within a greatly reduced thermoneutral zone, i.e., the Tc region between the upper (sweating) and lower (shivering) thresholds. This is due in part, but not entirely, to estrogen depletion at menopause. Elevated central sympathetic activation, mediated through α2-adrenergic receptors, is one factor responsible for narrowing of the thermoneutral zone. Procedures which reduce this activation, such as paced respiration and clonidine administration, ameliorate HFs as will peripheral cooling. HFs are responsible for some, but not all, of the sleep disturbance reported during menopause. Recent work calls into question the role of serotonin in HFs. This article is part of a Special Issue entitled 'Menopause'.

Postmenopausal physiological changes

The hallmark of menopause is the marked reduction of estradiol levels due to ovarian failure. This, among other factors result in hot flashes, the most common menopausal symptom. Hot flashes (HFs) can be measured objectively, both inside and outside the laboratory, using sternal skin conductance, an electrical measure of sweating. We have found that HFs are triggered by small elevations in core body temperature (T C ), acting within a greatly reduced thermoneutral zone. This reduction is caused by elevated central sympathetic activation, among other factors. There is a circadian rhythm of HFs peaking at 1825 h. Imaging studies have shown that hot flash activation begins in the brainstem, followed by the insula and by the prefrontal cortex. HFs in the first, but not the second half of the night can produce awakenings and arousals. This is because rapid eye movement (REM) sleep suppresses thermoregulatory effector responses, which include hot flashes.

Circadian rhythm of hot flashes and activity levels among prostate cancer patients on androgen deprivation therapy

OBJECTIVE

Altered circadian rhythms have been identified in untreated prostate cancer patients. Findings of restored rhythmicity following cancer treatment may have relevance for cancer control and symptom management. This study assessed and compared the cyclic patterns of hot flashes and activity levels in treated prostate cancer patients.

METHODS

Data were collected during two 24-h periods among 47 prostate patients undergoing androgen deprivation therapy (ADT). Hot flashes were detected objectively through sternal skin conductance and by patients via electronic event marking. Activity levels were recorded on a wrist actigraphy device.

RESULTS

The mean frequency of objectively measured and patient-reported hot flashes was 13.6 (SD = 14.3) and 12.6 (SD = 9.6), respectively. There were significant 24-h circadian rhythms of both hot flashes and activity levels. The peak of the rhythms occurred in early afternoon. There was no significant cross correlation between hot flashes and activity levels.

CONCLUSIONS

The acrophases of hot flashes and elevated activity levels in this study may represent a normalisation of circadian rhythms following ADT, pointing to the need for more research, including controlled, prospective chronobiologic studies. Future research may have important implications for the survival of prostate cancer patients and the identification of new and safe hot flash treatments.

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.

Increases in core body temperature precede hot flashes in a prostate cancer patient

OBJECTIVE

An effective and safe alternative treatment to hormone replacement therapy for hot flashes is needed for cancer patients. Interventions targeting the triggering mechanisms of hot flashes hold promise. Increases in core body temperature are a precursor of most hot flashes in women, and similar findings in prostate cancer patients undergoing androgen deprivation therapy would support further research in this area. We present preliminary findings of physiological changes in a prostate cancer patient with frequent hot flashes.

METHODS

Physiological changes in sternal skin conductance, heart rate, and core body temperature were continuously measured during two 3.5 h laboratory sessions. Perceived characteristics of hot flashes were recorded in a diary.

RESULTS

Five hot flashes were reported during laboratory sessions. Severity and bother ratings were low. All hot flashes were accompanied by large increases in sternal skin conductance and moderate increases in heart rate. Core body temperature increased 0.11-0.32 degrees C prior to and fell 0.23-0.44 degrees C following the peak increase in skin conductance.

CONCLUSIONS

This case study suggests that hot flashes in men may be preceded by increases in core body temperature. Identification of behavioral factors that raise core body temperature may lead to specific treatment strategies to reduce the frequency of hot flashes.

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 > or =4 hot flashes/day underwent laboratory hot flash testing with skin conductance measurement. Hot flashes were quantified with conventional (> or =2 micromho, 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.