Evidence map›Paper›PMID 41606583›Full record

ArticleBMC women's health2026

Within-individual changes in BMI and menstrual irregularity: a cohort study using real-world data.

Shiori Itoi, Makiko Sampei, Takayuki Tatsumi, Risa Ishida, Gentaro Izumi, Yutaka Osuga, Kaori Koga, Satoshi Narumi, Naho Morisaki

Abstract read
PubMed Full text at PMC Publisher
In one paragraph

Article in BMC women's health, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.

0numbers the graph read from it
0cells of the map it votes in
0citing papers in PubMed
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1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

0 citing papers in PubMed.

No citing paper in PubMed yet.

4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

9 authors.

Shiori ItoiDepartment of Social Medicine, National Center for Child Health and Development Research Institute, 2-10-1 Okura, Setagaya, Tokyo, 157-8535, Japan. shioriitoi@gmail.com.
Makiko SampeiDepartment of Nursing and Social Epidemiology, Nippon Sport Science University, Tokyo, Japan.
Takayuki TatsumiDivision of Reproductive Medicine, National Center for Child Health and Development Research Institute, Tokyo, Japan.
Risa IshidaDepartment of Obstetrics and Gynecology, The University of Tokyo, Tokyo, Japan.
Gentaro IzumiDepartment of Obstetrics and Gynecology, The University of Tokyo, Tokyo, Japan.
Yutaka OsugaDepartment of Obstetrics and Gynecology, The University of Tokyo, Tokyo, Japan.
Kaori KogaDepartment of Obstetrics and Gynecology, The University of Tokyo, Tokyo, Japan.
Satoshi NarumiDepartment of Molecular Endocrinology, National Center for Child Health and Development Research Institute, Tokyo, Japan.
Naho MorisakiDepartment of Social Medicine, National Center for Child Health and Development Research Institute, 2-10-1 Okura, Setagaya, Tokyo, 157-8535, Japan.

Funding

Japan Agency for Medical Research and Development JP19gk0210023 and JP22gk0210033
6 · The paper itself

Abstract

backgroundThe impact of body mass index (BMI) on reproductive health is well-established, but the effect of within-individual changes in BMI on the menstrual cycle, a valuable and accessible indicator of reproductive health, remains less studied. This study aimed to investigate the association between changes in individuals’ BMI and menstrual irregularity.

methodsThis cohort study analyzed data from a widely used menstrual tracking app in Japan. Menstrual cycle logs were collected from January 2019 to March 2021, and background information from questionnaires (Wave 1: Jan-Mar 2020; Wave 2: May-Jun 2020). Long-term BMI changes were defined as changes from age 18 to Wave 2, and short-term changes were defined as changes from Wave 1 to Wave 2. BMI was categorized as underweight (15–18.4), normal (18.5–22.9), and overweight/obese (23–35). Menstrual irregularity was defined as an individual’s average cycle length ranging outside the 24–38 day range.

resultsA total of 126,008 cycles from 5,444 individuals were analyzed. Individuals with overweight/obesity who became normal weight long-term had significantly lower odds of menstrual irregularity (long-term: aOR 0.39, 95% CI 0.20–0.75; short-term: aOR 0.61, 95% CI 0.18–2.02) compared to those who remained overweight/obese. Conversely, increases from normal weight to overweight/obese increased the odds (long-term: aOR 2.02, 95% CI 1.50–2.71; short-term: aOR 2.53, 95% CI 1.31–4.90) compared to those who remained normal weight. No significant association was found for individuals with underweight.

conclusionWithin-individual changes in BMI influence menstrual irregularity. Long-term, but not short-term, reductions from overweight/obese BMI to the normal BMI category were associated with lower odds of irregular cycles, whereas increases from a normal BMI to overweight/obesity raised the risk. These findings highlight the importance of sustainable weight management in enhancing reproductive health.

Indexed as

Body Mass IndexMenstruation DisturbancesAdultCohort StudiesFemaleHumansJapanMenstrual CycleObesityOverweightSurveys and QuestionnairesThinnessYoung AdultBody mass indexMenstrual cycleObesityUnderweightWeight gainWeight loss

Identifiers

PMID41606583
PMCPMC12924516

What Socratic holds

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LicenceCC BY-NC-ND
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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the Socratic graph.