Estimation of Circadian Body Temperature Rhythm Based on Heart Rate in Healthy, Ambulatory Subjects

Abstract

Core body temperature is a reliable marker for circadian rhythm. As characteristics of the circadian body temperature rhythm change during diverse health problems, such as sleep disorder and depression, body temperature monitoring is often used in clinical diagnosis and treatment. However, the use of current thermometers in circadian rhythm monitoring is impractical in daily life. As heart rate is a physiological signal relevant to thermoregulation, we investigated the feasibility of heart rate monitoring in estimating circadian body temperature rhythm. Various heart rate parameters and core body temperature were simultaneously acquired in 21 healthy, ambulatory subjects during their routine life. The performance of regression analysis and the extended Kalman filter on daily body temperature and circadian indicator (mesor, amplitude, and acrophase) estimation were evaluated. For daily body temperature estimation, mean R-R interval (RRI), mean heart rate (MHR), or normalized MHR provided a mean root mean square error of approximately 0.40 °C in both techniques. The mesor estimation regression analysis showed better performance than the extended Kalman filter. However, the extended Kalman filter, combined with RRI or MHR, provided better accuracy in terms of amplitude and acrophase estimation. We suggest that this noninvasive and convenient method for estimating the circadian body temperature rhythm could reduce discomfort during body temperature monitoring in daily life. This, in turn, could facilitate more clinical studies based on circadian body temperature rhythm.

Recent advances in modulators of circadian rhythms: an update and perspective

“…Circadian rhythm is the result of natural selection during the longterm evolution of organisms, enabling organisms to better adapt to changes in the external environment 1,2 . Various behaviours and physiological functions of the body show obvious circadian rhythms, such as the sleep-wake cycle 3,4 , food intake and other autonomous activities 5 , as well as physiological activities including blood pressure 6 , blood lipids, coagulation-fibrinolysis balance, heart rate 7,8 , body temperature 9 , locomotor activity 10,11 , hormone levels 12 , cell metabolism 13 , and cell proliferation 14,15 . The generation, maintenance, and regulation of circadian rhythms depend on the synergy of the circadian clock system, circadian input system, and circadian output system at the overall level (Figure 1) and at the cellular level, relying on the precise regulation of the endogenous circadian clock gene network (Figure 2).…”

Circadian Rhythm of Heart Rate Assessed by Wearable Devices Tends to Correlate with the Circadian Rhythm of Salivary Cortisol Concentration in Healthy Young Adults

“…Various modern smart watches and wearable activity trackers feature an optical sensor that can estimate the wearer's heart rate. Heart rate monitoring has recently been reported to be a noninvasive and convenient method for estimating the circadian rhythm of CBT [10].…”

Estimating Resting Core Temperature Using Heart Rate

“…Heart rate (HR)-based CT estimation models have been used to estimate resting CT and circadian rhythms under free-living conditions (Sim et al, 2016). ECTemp ™ is a HR-based core temperature (CT) estimation algorithm used mainly as a realtime thermal strain indicator in military populations (Buller et al, 2013;Buller, Tharion, Duhamel, & Yokota, 2015).…”