Introduction The menstrual cycle characteristics are essential to sexual and reproductive healthcare. Exposure to high altitudes reduces blood oxygen pressure and may result in hypoxia and mountain sickness. Data concerning its impact on menstruation is lacking.

Methods We conducted an opportunistic cross-sectional survey to study the menstrual cycles and the prevalence of dysmenorrhea in residents living above 3500 m in the Andean mountains. We measured dysmenorrhea on a 10-grade scale and evaluated bleeding based on the validated menstrual bleeding questionnaire. The covariates included socio-demographical, anthropometrical, and medical data.

Results one hundred thirty-six subjects from Argentina (6%), Bolivia (39%), and Peru (55%) were included (81% response rate). Most women had regular menstrual cycles and menarche at 13 years of age. Seven out of ten participants did not use contraception. The median menstrual pain score was 3.9 (interquartile range 2.8) with an estimated population mean of 3.7 ± 0.4, but 23.6% of participants had moderate to severe dysmenorrhea (grade 2-3). Dysmenorrhea and heavy menstrual bleeding were more prevalent with increasing altitude. There was no significant association between parity or breastfeeding and dysmenorrhea, while the use of hormonal contraception significantly decreased the severity of pain. Nearly 20% considered their menstruation normal despite having symptoms consistent with heavy menstrual bleeding. All women denied having any known gynecological illnesses. Heavy menstrual bleeding and severe dysmenorrhea were inversely associated with the education level. Only 22.8% had previously sought medical attention because of dysmenorrhea, 42% needed to take analgesics, and most preferred natural remedies such as herbal preparations (62%).

Discussion Our findings reflect a lack of menstrual education and underdiagnosis of gynecological—especially uterine— disorders in these rural and remote populations. Various coping mechanisms (endogenous antioxidant activity, dietary antioxidants, genetic modifications, etc.) can explain the adaptation and low intensity of pain, but the impact of high altitude and hypoxia on sexual and reproductive health is complex and poorly understood.

Conclusions Andean high-altitude residents (living above 3500 m) have delayed menarche, regular menstrual cycles, and low average menstrual pain. However, the prevalence of moderate to severe dysmenorrhea and heavy menstrual bleeding is high and should be studied in more depth. High altitude appears to influence menstrual pain and bleeding; this should be evaluated further in a larger controlled trial comparing sea-level with high Andean residents. More studies are needed to understand the needs of this special population in terms of menstrual education and sexual and reproductive healthcare.

The authors have declared no competing interest.

This study did not receive any funding

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