Nocturnal finger skin temperature in menstrual cycle tracking: ambulatory pilot study using a wearable Oura ring

Abstract

BackgroundBody temperature is a common method in menstrual cycle phase tracking because of its biphasic form. In ambulatory studies, different skin temperatures have proven to follow a similar pattern. The aim of this pilot study was to assess the applicability of nocturnal finger skin temperature based on a wearable Oura ring to monitor menstrual cycle and predict menstruations and ovulations in real life.MethodsVolunteer women (n = 22) wore the Oura ring, measured ovulation through urine tests, and kept diaries on menstruations at an average of 114.7 days (SD 20.6), of which oral temperature was measured immediately after wake-up at an average of 1.9 cycles (SD 1.2). Skin and oral temperatures were compared by assessing daily values using repeated measures correlation and phase mean values and differences between phases using dependent t-test. Developed algorithms using skin temperature were tested to predict the start of menstruation and ovulation. The performance of algorithms was assessed with sensitivity and positive predictive values (true positive defined with different windows around the reported day).ResultsNocturnal skin temperatures and oral temperatures differed between follicular and luteal phases with higher temperatures in the luteal phase, with a difference of 0.30 °C (SD 0.12) for skin and 0.23 °C (SD 0.09) for oral temperature (p < 0.001). Correlation between skin and oral temperatures was found using daily temperatures (r = 0.563, p < 0.001) and differences between phases (r = 0.589, p = 0.004). Menstruations were detected with a sensitivity of 71.9–86.5% in window lengths of ±2 to ±4 days. Ovulations were detected with the best-performing algorithm with a sensitivity of 83.3% in fertile window from − 3 to + 2 days around the verified ovulation. Positive predictive values had similar percentages to those of sensitivities. The mean offset for estimations were 0.4 days (SD 1.8) for menstruations and 0.6 days (SD 1.5) for ovulations with the best-performing algorithm.ConclusionsNocturnal skin temperature based on wearable ring showed potential for menstrual cycle monitoring in real life conditions.

Ultradian rhythms in heart rate variability and distal body temperature anticipate onset of the luteinizing hormone surge

“…Each of the 28 ( n = 20 premenopausal, n = 5 perimenopausal, n = 3 premenopausal and became pregnant) participants collected 2 to 3 cycles of data for analysis. For all cycles, the Oura Ring, a DBT, HRV (RMSSD), HR, and sleep sensor, was worn continuously on the finger, as previously described 65 , 98 . For all cycles, LH was monitored via urinary test strips (Wondfo Biotech Co., Guangzhou, China) from day 10 (with first day of menstruation considered day 1) until a positive reading was detected, and subsequently until 2 days after LH fell below the limit of detection (see below for details on the Urinary Hormone Assay, Luteinizing Hormone ).…”

“…Cycles were included in the premenopausal data set as likely ovulatory by four criteria a) one or more localized days of supra-threshold LH concentration, b) the presence of a rise in E2 (if collected) within typical range prior to or coincident with supra threshold LH, c) a subsequent rise in αPg and βPg (if collected), and d) positive values of DBT deviation, as previously described 98 , within 2 days of surge onset until the end of the cycle (See Supplemental Fig. 1 ).…”

Ultradian Rhythms in Heart Rate Variability and Distal Body Temperature Anticipate the Luteinizing Hormone Surge Onset

“…Each of the 28 (n=20 premenopausal, n=5 perimenopausal, n=3 premenopausal and became pregnant) participants collected 2 to 3 cycles of data for analysis. For all cycles, the Oura© Ring a distal body temperature (DBT), HRV (RMSSD), Heart Rate (HR) and sleep sensor, was worn continuously on the finger, as previously described (de Zambotti et al, 2017;Maijala et al, 2019). For all cycles, LH was monitored via urinary test strips (Wondfo Biotech Co., Guangzhou, China) from day 10 (with first day of menstruation considered day 0) until a positive reading was detected, and subsequently until 2 days after LH fell below the limit of detection (see below for details on the Urinary Hormone Assay, Luteinizing Hormone).…”

“…Inclusion and Exclusion Criteria for Collected Cycles. Cycles were included in the premenopausal data set as likely ovulatory by four criteria a) one or more localized days of suprathreshold LH concentration, b) the presence of a rise in E2 (if collected) within typical range prior to or coincident with supra threshold LH, c) a subsequent rise in αPg and βPg (if collected), and d) positive values of DBT deviation, as previously described (Maijala et al, 2019), within 2 days of surge onset until the end of the cycle (See Supplemental Figure 1). Cycles without E2, αPg and βPg data were included by meeting criteria a and d only.…”

Human Adaptations to Multiday Saturation on NASA NEEMO

“…Aquanauts were evaluated for sleep quantity, quality, respiration and skin temperature throughout rest (sleep) using OURA which is a 15 g multisensory technology ( de Zambotti et al, 2017 ; Maijala et al, 2019 ). This technology uses infrared light and a photosensor to gather beat-by-beat blood volume pulse architecture on the dominant ring finger palmar artery.…”