This study is designed to characterize a new quantitative method for measuring sweat production induced by controlled heat exposure. Approximately 20 healthy volunteers and up to 10 patients with ROSAH syndrome will be enrolled. Sweat production will be quantified using a gravimetric filter-paper technique during standardized 30-minute heat exposure in a temperature-controlled sauna chamber. Each participant will complete three repeated testing sessions. The study will also pilot a questionnaire to evaluate the self-reported impact and severity of hypohidrosis/anhidrosis.
This multicenter, controlled-environment, repeated-measures study is designed as a physiological challenge test. The study will be initiated in healthy volunteers to characterize the feasibility, reproducibility, and reference distribution of the sweat measurement method under controlled heat exposure. Upon confirmation of the method's suitability, the study will proceed to enroll participants with ROSAH syndrome. Each participant will complete three heat-exposure sessions in a sauna, separated by 1-3 days, with all sessions completed within a maximum of one week. The primary outcome is Total Gravimetric Sweat Production (TGSP). Safety evaluations will include monitoring of adverse events, vital signs, and body temperature.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
OTHER
Masking
NONE
Enrollment
30
Participants will drink 300 mL of water before testing and will sit in a temperature-controlled sauna chamber for approximately 30 minutes. The mean internal exposure temperature will be maintained above 42°C and below 44°C, with an adjustable nominal operating set point of approximately 45°C. Preweighed filter papers will be attached to prespecified anatomical sites and will be removed and reweighed immediately after exposure using a calibrated analytical balance. Body temperature, heart rate, symptoms, sauna temperature, and relative humidity will be monitored. The procedure will be stopped early if prespecified safety or intolerance criteria are met. The procedure will be repeated three times, with sessions at least 1 day apart and completed within 7 days.
Total Gravimetric Sweat Production (TGSP)
TGSP is defined as the sum of sweat mass collected from all prespecified and evaluable anatomical sites during a standardized heat-exposure session. For each site, sweat mass is calculated as the post-exposure filter paper weight minus the pre-exposure filter paper weight. TGSP will be reported in milligrams and may also be standardized by filter paper area according to the statistical analysis plan.
Time frame: During each of three approximately 30-minute heat-exposure sessions, with sessions at least 1 day apart and all three sessions completed within 7 days.
Regional Gravimetric Sweat Production by Anatomical Site
Sweat mass at the chest, back, axilla, forehead, and forearm will be calculated separately as the post-exposure filter paper weight minus the pre-exposure filter paper weight. Results will be reported in milligrams and may also be standardized by filter paper area.
Time frame: During each of three approximately 30-minute heat-exposure sessions, with sessions at least 1 day apart and completed within 7 days.
Test-Retest Reliability of Total Gravimetric Sweat Production
Short-term test-retest reliability of TGSP across the three heat-exposure sessions will be assessed using the intraclass correlation coefficient and graphical repeated-measures assessments.
Time frame: Across the three heat-exposure sessions completed within 7 days.
Within-Participant Variability of Total Gravimetric Sweat Production
Within-participant variability in TGSP across the three sessions will be summarized using within-participant standard deviation and coefficient of variation.
Time frame: Across the three heat-exposure sessions completed within 7 days.
Test-Retest Reliability and Variability of Regional Sweat Production
Test-Retest Reliability and Variability of Regional Sweat Production
Time frame: Across the three heat-exposure sessions completed within 7 days.
Total and Regional Sweat Production by Clinical Group, Sex, and Age Category
TGSP and regional sweat production will be summarized descriptively by clinical group (healthy volunteers and participants with ROSAH syndrome), sex, and age category (adolescents and adults). Comparisons are exploratory and are not powered for confirmatory hypothesis testing.
Time frame: During the three heat-exposure sessions completed within 7 days.
Sauna Chamber Temperature Stability
Sauna chamber temperature will be recorded continuously or at protocol-defined frequent intervals. Stability will be summarized using descriptive statistics and the extent of time within the protocol-defined operating range.
Time frame: Throughout each approximately 30-minute heat-exposure session during the three sessions completed within 7 days.
Sauna Chamber Relative Humidity Stability
Sauna chamber relative humidity will be recorded continuously or at protocol-defined frequent intervals and summarized descriptively to characterize environmental consistency across sessions.
Time frame: Throughout each approximately 30-minute heat-exposure session during the three sessions completed within 7 days.
Change in Body Temperature During Controlled Heat Exposure
Body temperature will be measured before sauna entry, at least every 5 minutes during exposure if not continuously monitored, at the end of exposure, and during recovery when clinically indicated. Change from the pre-exposure value and maximum observed temperature will be summarized.
Time frame: Before, during, immediately after, and during recovery from each of the three heat-exposure sessions completed within 7 days.
Heat-Exposure Sessions Terminated Early Due to Body Temperature of 38.0°C or Higher or Participant Intolerance
The number and percentage of planned heat-exposure sessions that are terminated early because body temperature reaches or exceeds 38.0°C, the participant requests discontinuation, or the investigator identifies clinically significant intolerance will be summarized.
Time frame: During the three heat-exposure sessions completed within 7 days.
Incidence, Type, and Severity of Adverse Events and Heat-Related Intolerance Events
Adverse events and procedure-related intolerance events will be collected and summarized by event type, severity, seriousness, and relationship to study procedures. Events of interest include heat intolerance, dizziness, presyncope or syncope, headache, nausea or vomiting, fatigue, palpitations, skin irritation, and clinically significant body-temperature elevation.
Time frame: From initiation of the first study procedure through the follow-up assessment, up to approximately 17 days per participant.
Anhidrosis/Hypohidrosis Impact Questionnaire Total Score
The questionnaire contains six scored items covering heat intolerance, frequency of overheating, activity limitation, use of cooling measures, perceived ability to sweat, and overheating-related symptoms. Each item is scored from 0 to 4; the total score ranges from 0 to 24, with higher scores indicating greater heat intolerance or impact of impaired sweating.
Time frame: Before the first heat-exposure session and 8 to 10 days after the final heat-exposure session.
Change in Anhidrosis/Hypohidrosis Impact Questionnaire Total Score
Change in questionnaire total score will be calculated as the follow-up total score minus the baseline total score. Item-level changes may also be summarized descriptively.
Time frame: From before the first heat-exposure session to 8 to 10 days after the final heat-exposure session.
Test-Retest Reliability of the Anhidrosis/Hypohidrosis Impact Questionnaire
Short-term stability and test-retest reliability of questionnaire total scores will be evaluated using paired descriptive summaries, correlations, intraclass correlation coefficients, and graphical assessments, as appropriate.
Time frame: Between the baseline assessment before the first heat-exposure session and the follow-up assessment 8 to 10 days after the final heat-exposure session.
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