Irregular and Long Periods Linked to NAFLD
Long or irregular menstrual cycles in relatively young women are linked an increased risk of both prevalent and incident nonalcoholic fatty liver disease (NAFLD), according to a cross-sectional study that included data on more than 70,000 women.
“Our results indicate that menstrual irregularity, which is easier to diagnose and usually presented earlier than PCOS [polycystic ovary syndrome] highlights the possibility of identifying premenopausal women at risk of developing NAFLD,” reported a team of authors primarily from Sungkyunkwan University, Seoul, South Korea.
The study evaluated women aged younger than 40 years who were participating in the Kangbuk Samsung Health Study, which involves a comprehensive biennial health examination at health centers in South Korea. Of the 135,090 women enrolled over a 6-year period who had at least one follow-up examination, 72,092 were available for analysis after excluding for a sizable list of confounding factors such as liver disease and infections; exposure to steatogenic medications, such as corticosteroids; hysterectomy; and pregnancy.
NAFLD Prevalence Climbs With Longer Menses
Of these women, 36.378 (27.7%) had menstrual cycles of 26-30 days and were identified as the index group. The prevalence of NAFLD in this group was 5.8%. For those with a menstrual cycle of 31-39 days, the prevalence rate climbed to 7.2%. For those with a menstrual cycle of at least 40 days or too irregular to estimate, the prevalence was 9.7%. The prevalence was 7.1% for those with a menstrual cycle less than 21 days.
The results of this study were published in the Journal of Clinical Endocrinology & Metabolism.
In those without NAFLD at baseline who were then followed for a mean of 4.4 years, there were 4,524 incident cases of NAFLD. Incidence density was calculated per 103 patient-years. In the index group, the rate was 18.4. It climbed to 20.2 for those with a menstrual cycle of 31-39 days and then to 22.9 for those with a menstrual cycle of at least 40 days. For those with a cycle of fewer than 21 days, the rate was 26.8.
After adjusting for age, body mass index, insulin resistance, and other confounders, the hazard ratio for incident NAFLD for those with long or irregular menstrual cycles compared with the incident group corresponded with a 22% increased risk (HR, 1.22; 95% confidence interval, 1.14-1.31). When calculated in a time-dependent analysis, the risk of NAFLD was increased by almost 50% (HR, 1.49; 95% CI, 1.38-1.60).
Risk Persists With Pcos Exclusion
PCOS has previously been associated with increased risk of NAFLD, but the association between long or irregular menstrual cycles and NAFLD persisted after women with PCOS were excluded.
The mechanism that links menstrual irregularity with NAFLD is unclear, but the investigators said that estrogen exposure is implicated. In addition to a previously reported associated between low estradiol levels and antiestrogens such as tamoxifen with increased risk of NAFLD, they cited studies associating estrogen replacement therapy with a reduced risk of NAFLD. The role of estrogen in suppressing inflammation, oxidative stress, and insulin resistance are all activities that might link more regular menses with a reduced risk of NAFLD, the authors contended.
Women older than 40 years were excluded from this analysis to reduce the possibility of perimenopausal changes as a confounding factor.
Of study limitations acknowledged by the investigators, the presence of NAFLD was diagnosed on ultrasonography rather than histology. Information on sex hormone or prolactin levels was not captured in relation to NAFLD incidence, and the lack of exposure to estrogen replacement therapy and oral contraceptives was based on self-reports from the participants.
Still, the large study size and the consistency of results after adjustment for multiple risk factors argue that long and irregular menstrual cycles do identify women at risk for NAFLD. One implication is that irregular menses can be a marker for NAFLD risk.
“Our findings do not prove a causal relationship, but they show that long or irregular menstrual cycles were significantly associated with an increased risk of developing NAFLD,” said Seungho Ryu, MD, PhD, a professor at the Sungkyunkwan University. Senior author of this study, Ryu emphasized in an interview that the association “was not explained by obesity or any other risk factor for NAFLD.”
Lifestyle Changes May Lower Risk
The message is that “young women with long or irregular menstrual cycles may benefit from lifestyle changes to reduce the risk of NAFLD,” Ryu stated.
The Study of Women’s Health Across the Nation, which was started in 1994, has not evaluated NAFLD, but it did show a relationship between longer menstrual cycles and more cardiometabolic risk factors, according to Nanette Santoro MD, professor and chair, department of obstetrics & gynecology, University of Colorado at Denver, Aurora.
This suggests that others are “thinking along the same lines,” but in discussing this study with this news organization, she characterized some of the design elements as well as some of the findings in this study as “peculiar.”
In addition to a “very, very narrow definition of regular cycles,” she questioned the consistent hazard ratio for NAFLD for those with long cycles relative to other types of irregular menses. Presuming that the group with longer cycles would have included at least some patients with undiagnosed PCOS, she was would have expected that the risk would have been highest in this group. While conceding that differences in body composition of Korean women is a potential explanation for this apparent discrepancy, “I would like to see confirmed in other samples of women with more detailed metabolic assessments to understand who is at risk,” she said.
Not least problematic for the strength of the conclusions, the hazard ratio for NAFLD among women with long or irregular menstrual cycles was “pretty low.” She described this as a level at which the risk “is very susceptible to confounding and unlikely to influence clinical practice.”
Anuja Dokras, MD, PHD, a professor of obstetrics and gynecology and director of the PCOS Center at the University of Pennsylvania, Philadelphia, also questioned whether undiagnosed PCOS might have skewed the data.
“There is increasing data on the association between PCOS and NAFLD. Irregular menses is a key criterion for PCOS, and PCOS is the commonest reason for anovulation,” she said. Dokras therefore considered it possible that patients with unrecognized PCOS were included in the study, weakening the claim that risk of NAFLD and long menstrual cycles remains significant after controlling for PCOS.
Ryu and coinvestigators, Santoro, and Dokras reported no potential conflicts of interest.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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