Dissertation Defense: Sofiya Shreyer

Vasomotor symptoms (VMS), or hot flashes (HF) and night sweats (NS), affect up to 80% of individuals during the menopausal transition and are associated with impaired sleep, mood disturbance, and cardiovascular risk. Despite their prevalence, HF and NS are routinely treated as a single symptom category, with NS commonly defined as HF that occur at night. This dissertation challenges that assumption across three studies, establishing that HF and NS are distinct phenomena requiring separate definitions, detection criteria, and investigation.

Chapter 1 examines whether HF and NS can be differentiated using physiological, self-reported, and qualitative data. NS were significantly longer than HF, occurred earlier in the night, and were described by participants as prolonged full-body sweating events distinct from the acute heat of HF. Subjective but not objective VMS were associated with sleep, stress, and depression. Chapter 2 investigates whether HF and NS are preceded by distinct short-term fluctuations in ambient temperature and humidity. HF and NS differed in their environmental antecedents in the 30 minutes before each event, further supporting the interpretation that the two symptoms arise through distinct physiological mechanisms. Chapter 3 applies Gaussian mixture modeling to objective electrodermal activity event metrics to develop a data-driven classification framework for nocturnal VMS. Four morphologically distinct event types were identified, including a slow-sustained event consistent with the objective signature of NS, a profile that would not be captured by standard HF detection criteria, providing the first empirical foundation for objective NS detection in ambulatory EDA data. Together, these findings establish HF and NS as distinct nocturnal phenomena and lay the groundwork for more precise research into their respective mechanisms, correlates, and health consequences.