Menstrual cycle length variation by demographic characteristics from the Apple Women's Health Study

Huichu Li; Elizabeth A Gibson; Anne Marie Z Jukic; Donna D Baird; Allen J Wilcox; Christine L Curry; Tyler Fischer-Colbrie; Jukka-Pekka Onnela; Michelle A Williams; Russ Hauser; Brent A Coull; Shruthi Mahalingaiah

doi:10.1038/s41746-023-00848-1

Menstrual Cycle Cycle Across the Lifespan

Menstrual cycle length variation by demographic characteristics from the Apple Women's Health Study

Li H, Gibson EA, Jukic AMZ, Baird DD, Wilcox AJ, Curry CL, Fischer-Colbrie T, Onnela JP, Williams MA, Hauser R, Coull BA, Mahalingaiah S

Published May 29, 2023 NPJ digital medicine, 6(1), 100

DOI 10.1038/s41746-023-00848-1 PMID 37248288 PMC PMC10226714

RRM Academy Synopsis

Menstrual cycles shorten with age until 50 in a large US app cohort

In the Apple Women's Health Study, a US digital cohort of 12,608 participants, cycle length shortened with age until 50, then lengthened. Cycle variability was highest above age 50. On average, cycles were longer for Asian and Hispanic participants than for white participants, and longer with higher BMI.

Key Findings

The analysis covered 165,668 cycles from 12,608 participants. Cycle length had a median of 28 days, with 5th to 95th percentiles of 22 to 38 days.
Cycles were 1.6 days longer (95%CI: 1.2, 2.0) for Asian participants and 0.7 days longer (95%CI: 0.4, 1.0) for Hispanic participants than for white participants.
Participants with BMI of 40 kg/m2 or higher had cycles 1.5 days longer than participants with a healthy BMI.
Cycle variability was lowest at ages 35 to 39 and about 200% higher above age 50. Long cycles were more likely above age 50 (OR = 6.47, 95%CI: 5.25, 7.98).
Asian participants had higher odds of a long cycle than white participants (OR = 1.43, 95%CI: 1.17, 1.75), as did Hispanic participants (OR = 1.26, 95%CI: 1.07, 1.48).

Interpretation

The Apple Women's Health Study is a prospective digital cohort, so the results describe associations among app users who tracked their bleeding. Participants with PCOS, uterine fibroids or a hysterectomy were excluded. The authors note that cycle data and all covariates were self-reported. Earlier reports from Japan, China and India described cycles approximately 1 to 2 days longer than in white populations, which the authors take as a possible sign that suggested cycle ranges may not apply across ethnic backgrounds.

RRM Context

Cycle length and regularity serve as a vital sign, as the authors state. Fertility awareness charting gives each woman her own baseline of length and variability, which population averages like these only approximate. The age pattern, with the least variability at ages 35 to 39, offers context for reading a chart at different life stages.

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

Abstract

Menstrual characteristics are important signs of women's health. Here we examine the variation of menstrual cycle length by age, ethnicity, and body weight using 165,668 cycles from 12,608 participants in the US using mobile menstrual tracking apps. After adjusting for all covariates, mean menstrual cycle length is shorter with older age across all age groups until age 50 and then became longer for those age 50 and older. Menstrual cycles are on average 1.6 (95%CI: 1.2, 2.0) days longer for Asian and 0.7 (95%CI: 0.4, 1.0) days longer for Hispanic participants compared to white non-Hispanic participants. Participants with BMI ≥ 40 kg/m2 have 1.5 (95%CI: 1.2, 1.8) days longer cycles compared to those with BMI between 18.5 and 25 kg/m2. Cycle variability is the lowest among participants aged 35-39 but are considerably higher by 46% (95%CI: 43%, 48%) and 45% (95%CI: 41%, 49%) among those aged under 20 and between 45-49. Cycle variability increase by 200% (95%CI: 191%, 210%) among those aged above 50 compared to those in the 35-39 age group. Compared to white participants, those who are Asian and Hispanic have larger cycle variability. Participants with obesity also have higher cycle variability. Here we confirm previous observations of changes in menstrual cycle pattern with age across reproductive life span and report new evidence on the differences of menstrual variation by ethnicity and obesity status. Future studies should explore the underlying determinants of the variation in menstrual characteristics.

Topics

Menstrual Cycle › Cycle Across the Lifespan › Cycle and General Health · Longevity and Reproductive Aging › Reproductive Aging › Cycle Changes With Age · Perimenopause and Menopause › Transition Physiology › Cycle Changes

Huichu Li, Elizabeth A Gibson, Anne Marie Z Jukic, Donna D Baird, Allen J Wilcox, Christine L Curry, Tyler Fischer-Colbrie, Jukka-Pekka Onnela, Michelle A Williams, Russ Hauser, Brent A Coull, Shruthi Mahalingaiah

H Li, Liz Gibson, Beth Gibson, Betsy Gibson, E Gibson, A Jukic, D Baird, A Wilcox, Chris Curry, C Curry, T Fischer-Colbrie, J Onnela, M Williams, R Hauser, B Coull, S Mahalingaiah

PMID 37248288 37248288 DOI 10.1038/s41746-023-00848-1 10.1038/s41746-023-00848-1 Li et al. 2023, Li 2023

Menstrual cycle length variation by demographic characteristics from the Apple Women's Health Study

Menstrual cycles shorten with age until 50 in a large US app cohort

Key Findings

Interpretation

RRM Context

Abstract

Topics

By this author

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