Did you know that we have nearly 3.5 trillion clocks in our bodies that affect things like our organs, weight, sleep and fertility? Most of these clocks in our bodies function on a 24-hour cycle, and are referred to as circadian rhythms. Owing to the rotation of the earth around its own axis, plants and animals have evolved around a 24-hour light-dark cycle. Circadian rhythms are biochemical, physiological, and behavioral cycles that run on a 24-hour period thanks to the planet we evolved on. They are essential for our well-being and when the clocks are off, they have been linked to weight gain, sleep deprivation, and even diseases. Core temperature is the most reliable biomarker for circadian rhythm, meaning that if you can measure core temperature, then you can see patterns in your circadian rhythms and assess how your clocks are working (1).
Sixteen years ago, researcher Mary Coyne and her team confirmed that women’s menstrual and fertility cycles reliably tracked by continuous core body temperature (2). By measuring continuous core temperature, they found a distinct circadian rhythm that can detect the phases of a woman’s menstrual cycle and predict impending ovulation. They noticed that about 2 days before ovulation, there is a subtle dip in temperature. What this means is that if women could measure their core temperature continuously, they could predict impending ovulation and detect whether or not they ovulated with a 99% accuracy (2).
Learn more about how circadian rhythm can predict ovulation.
So how do we measure temperature throughout the day to get the same results as the study? Since temperature can be affected by external cues, only core temperature can be the most reliable way to measure circadian rhythms. While there are sensors out on the market that measure temperature from your ear, mouth or wrist, core body temperature is far and away the most accurate. In fact, literature shows that using peripheral thermometers do not provide accurate readings and should not be used to influence clinical decisions (3). Dr. Wade Webster explains that skin peripheral temperature lacks correlation with core in most circumstances. As one begins to sweat,an example, skin temperature drops while core temperature begins to climb when you sweat.
What is the most reliable way then to get core temperature readings to predict ovulation? The answer is simply to measure vaginal core temperature since there are no external factors such as eating, drinking, or breathing that interfere with the results. Ok, we know what you are thinking - how in earth are you going to take vaginal temperature readings throughout the day and night? Well, with technology quickly advancing, products are entering the market that can measure your core temperature effortlessly. For example, here at Prima-Temp, we are building a mobile phone platform that uses circadian rhythm from core temperature for predicting ovulation. We are super excited for our first product, Priya, to be on the market early 2017. Learn more about Priya here and sign up to be notified when Priya is ready to be shipped to your doorstep.
- Brown et al. (2000). A statistical model of the human core-temperature circadian rhythm. Am J Physiol Endocrinol Metab 279: E669–E683.
- Coyne et al. (2000). Circadian Rhythm Changes in Core Temperature over the Menstrual Cycle: Method for Noninvasive Monitoring Physiol Regulatory Integrative Com Physiol. AM J 279:1316-132.
- Webster, W. https://www.linkedin.com/pulse/science-behind-priya-circadian-rhythm-part-4-wade-webster