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

Anna Maijala; Hannu Kinnunen; Heli Koskimäki; Timo Jämsä; Maarit Kangas

doi:10.1186/s12905-019-0844-9

Fertility Awareness · Technology

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

Maijala A, Kinnunen H, Koskimäki H, Jämsä T, Kangas M

Published November 29, 2019 BMC Women's Health, 19(1), 150

DOI 10.1186/s12905-019-0844-9 PMID 31783840 PMC PMC6883568

RRM Academy Synopsis

Nightly finger temperature on an Oura ring ran higher after ovulation

Finger skin temperature from an Oura ring ran higher after ovulation than before it, in a 2019 pilot of 22 women. The women also took urine ovulation tests. The best algorithm found about 8 out of 10 verified ovulations within a 6-day window.

Key Findings

Mean skin temperature was 0.30 °C (SD 0.12) higher in the luteal phase than the follicular phase. For oral temperature the gap was 0.23 °C (SD 0.09). Both p < 0.001.
Daily skin and oral temperatures correlated at r = 0.563 (p < 0.001, 95% CI 0.519–0.604).
Algorithm MENSES found the start of menstruation with a sensitivity of 81.4% within ±3 days and 86.5% within ±4 days.
Algorithm HALF_LOCS detected ovulation with a sensitivity of 83.3% in a window from 3 days before to 2 days after the verified ovulation day.
Skin temperature met the pre-defined 0.15 °C phase-difference requirement in 21 of 22 participants. Oral temperature met it in 18 of 22.

Interpretation

This pilot study followed 22 women wearing an Oura ring for an average of 114.7 days (SD 20.6) each. A urine hormone test verified ovulation in every cycle. Two participants had a BMI over 30, and none smoked. The findings support larger studies of wearable temperature tracking for cycle awareness.

RRM Context

Restorative reproductive medicine treats the cycle as clinical data. Evaluation comes before treatment. NaProTechnology and the Creighton Model use a temperature rise after ovulation as one marker they chart. This study checks that marker against urine tests and oral readings.

Our editorial summary of this paper, not the article's abstract.

Abstract

Background

Body 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.

Methods

Volunteer 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).

Results

Nocturnal 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.

Conclusions

Nocturnal skin temperature based on wearable ring showed potential for menstrual cycle monitoring in real life conditions.

Topics

Fertility Awareness › Technology › Wearable Devices · Menstrual Cycle › Cycle Biomarkers › Basal Body Temperature · Research Methods › Measurement and Statistics › Instrument Development and Validation

Anna Maijala, Hannu Kinnunen, Heli Koskimäki, Timo Jämsä, Maarit Kangas

A Maijala, H Kinnunen, H Koskimäki, T Jämsä, M Kangas

PMID 31783840 31783840 DOI 10.1186/s12905-019-0844-9 10.1186/s12905-019-0844-9 Maijala et al. 2019, Maijala 2019

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

Nightly finger temperature on an Oura ring ran higher after ovulation

Key Findings

Interpretation

RRM Context

Abstract

Topics

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