Hot flashes refer to a sudden sensation of being overheated followed by activation of cooling mechanisms such as sweating and vasodilation as well as cold-seeking behaviors such as throwing off blankets. The use of an ingested telemetry pill has established that asymptomatic postmenopausal women – like premenopausal women – have a thermo-neutral zone of approximately 0.4 °C in which neither warming mechanisms such as shivering nor cooling mechanisms such as sweating are activated, whereas symptomatic women enjoy no such buffer range. Consequently, symptomatic postmenopausal women virtually always feel either too hot or too cold to some degree. Thus, menopause-related vasomotor symptoms are characterized by acute reactions to ambient temperature stressors. In symptomatic menopausal women, warmer ambient temperatures can serve as a trigger for hot flashes and night sweats. Women over 50 already constituted more than 1/6th of the United States population in the 2010 Census and this share is expected to grow with the aging population. Current estimates suggest that about 75% of these women will experience hot flashes. A recent observational study of 1449 women entering menopause determined that the average duration of symptoms lasts nearly 7.5 years, with substantial numbers of cases presenting symptoms for over 11 years. The average duration of symptoms for black women specifically was 10.1 years. Given their prevalence and duration, it is unsurprising that a large and robust market has emerged for treatments offering relief of menopausal symptoms. Treatment of menopausal symptoms is segmented into hormonal and non-hormonal based approaches, both associated with drawbacks. One research firm, Transparency Market Research, estimates that the market for treatment of hot flashes in the United States will reach $5.28B by 2023. Estrogen treatments were vigorously promoted until the increased risks of hormonally-dependent cancers with such treatments were appreciated. There is growing recognition that despite the expense and clinical uncertainties of treating menopausal symptoms, the indirect costs of foregoing treatment may be even greater. Using insurance records to compare healthcare utilization and work productivity between untreated women with vasomotor symptoms (VMS) and matched controls, it was demonstrated that the VMS group had 82% more outpatient visits and 57% more lost workdays than controls. Existing non-pharmacological treatments for thermal dysregulation and sleep disturbance are unidirectional in the temperature change they can effect (they can only heat or only cool but not both) and may lead to temperature swings outside of a comfortable range. Some approaches may rely on direct heating (e.g., electric blankets, battery-powered warming socks and gloves), facilitate heat retention, (e.g., standard blankets, thermal underwear, flannel pajamas), or promote evaporative cooling (e.g., moisture-wicking sleepwear). To interrupt or arrest this temperature modulation effect in the event of discomfort, the sleeper typically must awaken to take off or exchange the garment or to throw off or pile on blankets. The discomfort produced by wide temperature swings and the physical effort required to retrieve blankets or change sleepwear during the night may lead to more frequent transient arousals and full awakenings. Our innovation allows sleepers to regulate skin temperature by wearing a simple and comfortable garment. It produces significant skin temperature changes by relying on the sleeper's own perceived need for warming or cooling. Our approach trains sleepers to use a behavior already present in sleep (the ability to change position to increase comfort) and extends this behavior to promote temperature regulation. The sensitivity of women with menopausal symptoms to ambient temperature changes suggests it may prove beneficial for them to maintain as narrow a temperature range as possible around their thermo-neutral boundary during sleep. Wearing specially constructed sleepwear – which we have dubbed “Janus Pajamas” – that promotes either thermal conduction or insulation depending upon body position will allow women to fine-tune skin temperature through movement. This will allow them to maintain skin temperature in a narrower range during sleep than is typically possible. Autonomic movements in pursuit of skin temperature regulation already exist, e.g., turning the pillow over to the cool side or adopting a fetal position to minimize exposed surface area and heat loss. These temperature-regulating behaviors happen outside of conscious control. We believe a person wearing Janus Pajamas will be able to effectively “steer” her body (turning to the left or right side) while asleep to maintain optimal conditions within the thermo-neutral zone. This should result in improved sleep architecture with fewer transient arousals and full awakenings.
