IntroductionLimited evidence exists to guide travelers about blood pressure (BP) changes at high altitude (HA). Our primary objective compared 24-h ambulatory BP at low altitude (LA) vs HA in a cohort of tourists. Exploratory analyses compared results by sex and history of underlying hypertension.MethodsThis prospective observational cohort study measured ambulatory BP with Welch-Allyn ABPM 6100 monitors at LA (<1000 m) and HA (median 2751 m). Measurements included heart rate/BP every 30 min while awake and hourly overnight, BP≥180/100 mm Hg, sleep quality, and Lake Louise score (acute mountain sickness).ResultsAmong 33 participants (median age 61 y, 17 with hypertension, 12 on BP medication), 25 completed LA and HA measurements. Average 24-h mean arterial pressure (MAP) increased at HA by 6 mm Hg (95% CI, 2-10 mm Hg; P=0.04). When analyzed by the presence of preexisting hypertension, 24-h MAP was similar between LA and HA in those with underlying hypertension (mean difference, 4 mm Hg; 95% CI, -4 to 11 mm Hg; P=0.3) but rose at HA in those without (mean difference, 9 mm Hg; 95% CI, 5-14 mm Hg; P=0.001). At HA, 24-h MAP was similar in both groups (mean difference, 9 mm Hg; 95% CI, 0-19 mm Hg; P=0.05). Results did not differ by sex. Severe-range BP was common in all groups and asymptomatic.ConclusionsAmong this tourist cohort, we observed an increase in average 24-h MAP at HA. Altitude-related changes in BP varied greatly between individuals. This variation was related in part to underlying hypertension but not sex. Our data suggest that BP changes are not of clinical concern in HA travelers.

Introduction Pregnant individuals benefit both psychologically and physically by participating in outdoor activities.Methods The authors conducted a narrative review of the available literature to address unique pregnancy considerations for the wilderness adventurer. There is limited evidence behind many opinion-based recommendations on participation in wilderness activities in pregnancy.Results As a result, remote or adventurous activities may be considered unsafe or restricted without significant medical literature to support these opinions. The authors reviewed the literature for the best available evidence, including observational studies, case series, limited controlled trials, and extrapolations from physiological data, as well as evaluating expert consensus statements.Conclusion This narrative review discusses pregnancy-specific medical concerns related to participation in outdoor adventure activities.

IntroductionAlthough rock climbing is approaching gender parity in participation, female representation in rock climbing research remains to be investigated. We evaluated the gender distribution of study participants and authorship in the rock climbing literature.MethodsWe conducted a systematic review with PubMed and Embase to identify original research articles involving rock climbers. We categorized articles by and extracted data on the sex (female and male) of study participants and authors. Author gender was classified with Genderize.io, an automated probability-based assessment software.ResultsWe identified 298 original research articles from 1973 to 2023. Among the 266 articles that reported study participant gender, females comprised 36% of climber participants. Eighty-two articles (31%) had all-male climber participants, whereas 7 articles (3%) had an all-female cohort. Female climbers were the most underrepresented in articles investigating chronic climbing injuries (13% female), imaging studies (15%), and injury rehabilitation (20%). Female representation was highest in studies about youth climbing (43%) and epidemiology (36%). Of 1360 total authorships, 290 (21%) were female. Females were first authors for 54 articles (18%) and last authors for 53 articles (18%). Articles with female first authors had a higher proportion of female study participants than those with male first authors (39 vs 36%; P<0.001), whereas the proportion was similar between female and male last authors (36 vs 36%; P=0.592).ConclusionsFemale representation in climbing research and authorship is limited. Most research has studied male climbers, limiting the ability to apply these results to female climbers.

BACKGROUND:Acute mountain sickness (AMS) is a debilitating condition that may occur on ascent to high altitude, with limited options for chemoprophylaxis. The pathophysiology of AMS is poorly understood, though it may be similar to migraine. This study aimed to determine the efficacy of prochlorperazine, a first-line agent for acute migraine, for AMS prophylaxis. METHODS:We performed a randomized, double-blind, placebo-controlled trial involving healthy, unacclimatized adult participants, primarily from the Denver area (1609 m), who received either oral prochlorperazine or placebo three times daily for 24 hours during rapid ascent to Mount Blue Sky, Colorado (4348 m). We evaluated individuals who received at least the first dose of placebo or intervention following a modified intent-to-treat approach. Participants travelled by vehicle to 3910 m, then hiked to the summit of Mount Blue Sky, where they slept overnight. The primary outcome was AMS incidence as defined by the 2018 Lake Louise Questionnaire, which was assessed on the evening of ascent and the following morning. RESULTS:We analysed 56 participants (25 women), with a mean age of 39 [IQR 28-49], with 28 participants in each study arm. Key baseline characteristics were equally distributed and well-matched between study arms. The incidence of AMS was 28 (50%), with 18 (64%) in the placebo arm and 10 (36%) in the prochlorperazine arm (P = 0.06). The absolute risk reduction was 28.6%, the number needed to treat was 4 and the odds ratio was 0.28 (95% C.I. 0.11-0.94). There were no serious adverse events, and there were no significant differences in the side effects between arms, including for drowsiness (P = 0.47). CONCLUSION:Our results suggest that prochlorperazine is effective in preventing AMS. Larger studies are warranted to validate our findings.

Acute mountain sickness (AMS) is a debilitating condition that individuals may develop on ascent to high altitude. It is characterized by headache, nausea, vomiting, dizziness, and fatigue with the potential to progress to fatal disease. Although the pathophysiology of AMS remains unclear, proposed mechanisms are hypothesized to be similar to migraine. Prochlorperazine, a first-line treatment for acute migraine, has been shown to abort migraine early and thus may be effective in preventing AMS. Its action as a respiratory stimulant additionally makes it a promising novel agent for AMS prevention. In this randomized double-blinded trial, participants will be randomized to receive oral prochlorperazine maleate or placebo for 24 h of three times daily dosing on a rapid ascent to 4348 m. Participants will be adults, aged 18, and older who are unacclimatized. Participants will remain at this elevation overnight. The Lake Louise Questionnaire will be utilized to define the primary outcome and presence of AMS and will be assessed the evening of and morning after ascent to peak altitude. Currently, acetazolamide is the preferred option for the chemoprophylaxis of AMS, which has been studied and utilized since the 1970s and involves potential prohibitive side effects. Other more efficacious options with more tolerable side effects are needed. Preventing AMS has the potential to limit both the morbidity and mortality associated with developing AMS and more serious diseases (notably high-altitude cerebral edema). Additionally, there is a substantial economic and environmental impact of AMS that could be prevented. Clinicaltrial.gov, NCT06450899. Registered on June 2024.

Gardner, Laurel, Linda E. Keyes, Caleb Phillips, Elan Small, Tejaswi Adhikari, Nathan Barott, Ken Zafren, Rony Maharjan, and James Marvel. Women at altitude: Menstrual-cycle phase, menopause, and exogenous progesterone are not associated with acute mountain sickness. High Alt Med Biol. 00:000-000, 2024. Background: Elevated progesterone levels in women may protect against acute mountain sickness (AMS). The impact of hormonal contraception (HC) on AMS is unknown. We examined the effect of natural and exogenous progesterone on the occurrence of AMS. Methods: We conducted a prospective observational convenience study of female trekkers in Lobuche (4,940 m) and Manang (3,519 m). We collected data on last menstrual period, use of exogenous hormones, and development of AMS. Results: There were 1,161 trekkers who met inclusion criteria, of whom 307 (26%) had AMS. There was no significant difference in occurrence of AMS between women in the follicular (28%) and the luteal (25%) phases of menstruation (p = 0.48). The proportion of premenopausal (25%) versus postmenopausal women (30%) with AMS did not differ (p = 0.33). The use of HC did not influence the occurrence of AMS (HC 23% vs. no HC 26%, p = 0.47), nor did hormonal replacement therapy (HRT) (HRT 11% vs. no HRT 31%, p = 0.13). Conclusion: We found no relationship between menstrual-cycle phase, menopausal status, or use of exogenous progesterone and the occurrence of AMS in trekkers and conclude that hormonal status is not a risk factor for AMS. Furthermore, women should not be excluded from future AMS studies based on hormonal status.

The Women in Wilderness Medicine Research Committee of the Wilderness Medical Society conducted a narrative review to address considerations for pregnant individuals in wilderness environments. There is limited evidence behind many opinion-based recommendations on the safety of various environmental exposures in pregnancy. The authors reviewed the literature for the best available evidence, including observational studies, case series, limited controlled trials, and extrapolation from physiological data, as well as evaluating expert consensus statements. The benefits of exposure to natural environments include better pregnancy outcomes and improved maternal mental and physical health. Risks are similar to nonpregnant individuals with the added risks associated with maternal-fetal physiology in wilderness environments and difficulties of evacuation. This narrative review discusses pregnancy-specific concerns in extreme environments, including high altitude, hypothermia, hyperthermia, lightning strikes, envenomations, and common outdoor exposures.

Millions of people visit high-altitude regions annually and more than 80 million live permanently above 2,500 m. Acute high-altitude exposure can trigger high-altitude illnesses (HAIs), including acute mountain sickness (AMS), high-altitude cerebral oedema (HACE) and high-altitude pulmonary oedema (HAPE). Chronic mountain sickness (CMS) can affect high-altitude resident populations worldwide. The prevalence of acute HAIs varies according to acclimatization status, rate of ascent and individual susceptibility. AMS, characterized by headache, nausea, dizziness and fatigue, is usually benign and self-limiting, and has been linked to hypoxia-induced cerebral blood volume increases, inflammation and related trigeminovascular system activation. Disruption of the blood-brain barrier leads to HACE, characterized by altered mental status and ataxia, and increased pulmonary capillary pressure, and related stress failure induces HAPE, characterized by dyspnoea, cough and exercise intolerance. Both conditions are progressive and life-threatening, requiring immediate medical intervention. Treatment includes supplemental oxygen and descent with appropriate pharmacological therapy. Preventive measures include slow ascent, pre-acclimatization and, in some instances, medications. CMS is characterized by excessive erythrocytosis and related clinical symptoms. In severe CMS, temporary or permanent relocation to low altitude is recommended. Future research should focus on more objective diagnostic tools to enable prompt treatment, improved identification of individual susceptibilities and effective acclimatization and prevention options. Acute or chronic exposure to elevations above 2,500 m can lead to altitude illnesses, including acute mountain sickness, high-altitude cerebral or pulmonary oedema, and chronic mountain sickness. In this Primer, Gatterer et al. summarize the epidemiology and pathophysiology of these disorders, discuss diagnosis, prevention and treatment, and highlight areas for future research.

Horakova, Lenka, Susi Kriemler, Vladimír Študent, Jacqueline Pichler Hefti, David Hillebrandt, Dominique Jean, Kastė Mateikaitė-Pipirienė, Peter Paal, Alison Rosier, Marija Andjelkovic, Beth Beidlemann, Mia Derstine, and Linda E. Keyes. Hormonal contraception and menstrual cycle control at high altitude: a scoping review-UIAA Medical Commission recommendations. High Alt Med Biol. 25:255-265, 2024. Background: Women who use hormonal contraception (HC) may have questions about their use during travel to high altitude. This scoping review summarizes current evidence on the efficacy and safety of HC and cycle control during high-altitude travel. Methods: We performed a scoping review for the International Climbing and Mountaineering Federation (UIAA) Medical Commission series on Women's Health in the Mountains. Pertinent literature from PubMed and Cochrane was identified by keyword search combinations (including contraception) with additional publications found by hand search. Results: We identified 17 studies from 7,165 potentially eligible articles. No articles assessed the efficacy of contraception during a short-term high-altitude sojourn. Current data show no advantage or disadvantage in HC users for acclimatization or acute mountain sickness (AMS). Use of HC during high-altitude travel is common and safe for menses suppression. A potential concern of estrogen-containing HC is the increased thrombotic risk, which theoretically could be compounded in hypobaric hypoxia. Conclusions: Evidence is limited for the interaction of HC and high altitude on performance, thrombosis, and contraceptive efficacy. HC does not affect the risk of AMS. The most efficacious and safest method at high altitude is generally the one women are most familiar with and already using.

Background: Acute mountain sickness (AMS) and high-altitude cerebral edema (HACE) are illnesses associated with rapid ascent to altitudes over 2,500 m in unacclimatized lowlanders. The aim of this scoping review is to summarize the current knowledge on sex differences in the epidemiology, pathophysiology, symptomatology, and treatment of AMS and HACE, especially in women. Methods and Results: The UIAA Medical Commission convened an international author team to review women's health issues at high altitude and to publish updated recommendations. Pertinent literature from PubMed and Cochrane was identified by keyword search combinations (including AMS, HACE, and high altitude), with additional publications found by hand search. The primary search focus was for articles assessing lowland women sojourning at high altitude. Results: The literature search yielded 7,165 articles, 37 of which were ultimately included. The majority of publications included did not find women at increased risk for AMS or HACE. There was extremely limited sex-specific data on risk factors or treatment. Conclusions: There is a limited amount of data on female-specific findings regarding AMS and HACE, with most publications addressing only prevalence or incidence with regard to sex. As such, general prevention and treatment strategies for AMS and HACE should be used regardless of sex.

Mateikaitė-Pipirienė, Kastė, Dominique Jean, Peter Paal, Lenka Horakova, Susi Kriemler, Alison J. Rosier, Marija Andjelkovic, Beth A. Beidleman, Mia Derstine, Jacqueline Pichler Hefti, David Hillebrandt, and Linda E. Keyes for the UIAA MedCom writing group on Women's Health in the Mountains. Menopause and high altitude: A scoping review-UIAA Medical Commission Recommendations. High Alt Med Biol. 25:1-8, 2024. Background: Older people are an important fraction of mountain travelers and climbers, many of them postmenopausal women. The aim of this work was to review health issues that older and postmenopausal women may experience at high altitude, including susceptibility to high-altitude illness. Methods: We performed a scoping review for the UIAA Medical Commission series on Women's Health in the mountains. We searched PubMed and Cochrane libraries and performed an additional manual search. The primary search focused on articles assessing lowland women sojourning at high altitude. Results: We screened 7,165 potential articles. The search revealed three relevant articles, and the manual search another seven articles and one abstract. Seven assessed menopausal low-altitude residents during a high-altitude sojourn or performing hypoxic tests. Four assessed high-altitude residents. We summarize the results of these 11 studies. Conclusions: Data are limited on the effects of high altitude on postmenopausal women. The effects of short-term, high-altitude exposure on menopause symptoms are unknown. Menopause has minimal effect on the physiological responses to hypoxia in physically fit women and does not increase the risk of acute mountain sickness. Postmenopausal women have an increased risk of urinary tract infections, which may be exacerbated during mountain travel. More research is needed on the physiology and performance of older women at high altitude.

ABSTRACT:Pregnant women are traveling to high altitude and evidence-based recommendations are needed. Yet, there are limited data regarding the safety of short-term prenatal high-altitude exposure. There are benefits to prenatal exercise and may be benefits to altitude exposure. Studies evaluating maternofetal responses to exercise at altitude found the only complication was transient fetal bradycardia, a finding of questionable significance. There are no published cases of acute mountain sickness in pregnant women, and data suggesting an increase in preterm labor are of poor quality. Current recommendations across professional societies are overly cautious and inconsistent. Non-evidence-based restrictions to altitude exposure can have negative consequences for a pregnant women's physical, social, mental, and economic health. Available data suggest that risks of prenatal travel to altitude are low. Altitude exposure is likely safe for women with uncomplicated pregnancies. We do not recommend absolute restrictions to high altitude exposure, but rather caution and close self-monitoring.

Horakova, Lenka, Peter Paal, Jacqueline Pichler Hefti, Marija Andjelkovic, Beth A. Beidleman, Mia Derstine, David Hillebrandt, Dominique Jean, Kastė Mateikaitė-Pipirienė, Alison J. Rosier, Susi Kriemler, and Linda E. Keyes. Women's health at high altitude: An introduction to a 7-part series by the International Climbing and Mountaineering Federation Medical Commission. High Alt Med Biol. 24:243-246, 2023. Background: Women have been traveling to high altitude since the inception of modern mountaineering. Although there are distinct female-specific features such as menstruation and menopause relevant to adaptation to and performance at high altitude, very little data exist on women's high-altitude health. To summarize what is known to date, the Medical Commission of the International Climbing and Mountaineering Federation (UIAA) has created a series of articles on women's health, high altitude illness, and performance at high altitude. Methods: Assembling an international author team, two types of manuscripts were developed: (1) reviews on female-specific topics such as pregnancy; (2) reviews on sex differences in high-altitude related illnesses, nutrition, cold injuries, and mortality. Results: The literature search yielded 7,165 articles, with 482 studies meeting the inclusion criteria for full-text review. The authors of individual chapters reviewed these articles and performed additional hand searches. Conclusions: Some important questions on women sojourning and exercising at high altitude have been studied, but many are still awaiting a qualified and evidence-based response. Our seven reviews, to be published in future issues of this journal, summarize what is known about lowland women sojourning at high altitude, provide recommendations, and highlight knowledge gaps in high altitude women's medicine.

Andjelkovic, Marija, Peter Paal, Susi Kriemler, Kaste Mateikaite-Pipiriene, Alison Rosier, Beth Beidleman, Mia Derstine, Jacqueline Pichler Hefti, David Hillebrandt, Lenka Horakova, Dominique Jean, and Linda E. Keyes. Nutrition in women at high altitude: a scoping review-UIAA Medical Commission recommendations. High Alt Med Biol. xx:xxx-xxx, 2023.Background: Nutritional concerns such as food composition, energy intake, and nutrient absorption are essential for performance at high altitude and may differ between men and women. We performed a scoping review to summarize what is currently known on nutrition for women during short-term, high-altitude, physically active sojourns.Methods: The UIAA Medical Commission convened an international team to review women's health issues at high altitude and to publish updated recommendations. Pertinent literature from PubMed and Cochrane was identified by keyword search combinations (including nutrition, metabolism, energy composition, micronutrients) with additional publications found by hand search.Results: We found 7,165 articles, of which 13 original articles assessed nutritional aspects in physically active women on short-term high-altitude sojourns, with other articles found by hand search. We summarize the main findings.Conclusions: Data on women's nutrition at altitude are very limited. Reduction in energy intake plus increased energy expenditure at high altitude can lead to unbalanced nutrition, negatively influencing high-altitude adaptation and physical performance. Therefore, adequate dietary and fluid intake is essential to maintaining energy balance and hydration at high altitude in women as in men. Iron supplementation should be considered for women with iron depletion before travel.

Kriemler, Susi, Kastė Mateikaitė-Pipirienė, Alison Rosier, Linda E. Keyes, Peter Paal, Marija Andjelkovic, Beth A. Beidleman, Mia Derstine, Jacqueline Pichler Hefti, David Hillebrandt, Lenka Horakova, and Dominique Jean; for the UIAA MedCom Writing Group on Women's Health in the Mountains. Frostbite and mortality in mountaineering women: a scoping review-UIAA Medical Commission recommendations. High Alt Med Biol. 24:247-258, 2023. Background: The harsh environment of high altitudes (HA) poses many serious health risks for mountaineers, including cold injuries and death. The aim of this work was to review whether female mountaineers are at special risk for frostbite or death at HA compared with their male counterparts. Methods: The UIAA Medical Commission convened an international author team to review women's health issues at HA and to publish updated recommendations. Pertinent literature from PubMed and Cochrane was identified with additional publications found by hand search. The primary search focus was for articles assessing cold injuries and death in women mountaineers at HA. Results: We reviewed the literature and identified 20 relevant studies: 2 studies on frostbite at HA, plus 7 studies and 1 report for death at HA. An additional 10 studies about frostbite at low altitude were included. We found that female mountaineers at HA were at lower risk of death than their male counterparts, but sex differences in frostbite were inconclusive. Conclusions: The frequency of cold injuries and mortality in female mountaineers is not yet well studied, and the studies that have been published tend to lack precise exposure data. More studies and registries with sex-differentiated data are needed.

Women increasingly participate in outdoor activities in wilderness and remote environments. We performed a literature review to address diagnostic and therapeutic considerations during first-trimester pregnancy for remote multiday travel. Pretrip planning for pregnant patients traveling outside access to advanced medical care should include performing a transvaginal ultrasound to confirm pregnancy location and checking D rhesus status. We discuss the risk of potential travel-related infections and recommended vaccinations prior to departure based on destination. Immediate evacuation to definitive medical care is required for patients with a pregnancy of unknown location and vaginal bleeding. We propose algorithms for determining the need for evacuation and present therapeutic options for nausea and vomiting, urinary tract infections, and candidiasis in the field.

To provide guidance to clinicians about best practices, the Wilderness Medical Society (WMS) convened an expert panel to develop evidence-based guidelines for prevention, diagnosis, and treatment of acute mountain sickness, high altitude cerebral edema, and high altitude pulmonary edema. Recommendations are graded based on the quality of supporting evidence and the balance between the benefits and risks/burdens according to criteria put forth by the American College of Chest Physicians. The guidelines also provide suggested approaches for managing each form of acute altitude illness that incorporate these recommendations as well as recommendations on how to approach high altitude travel following COVID-19 infection. This is an updated version of the original WMS Consensus Guidelines for the Prevention and Treatment of Acute Altitude Illness published in Wilderness & Environmental Medicine in 2010 and the subsequently updated WMS Practice Guidelines for the Prevention and Treatment of Acute Altitude Illness published in 2014 and 2019.

Pichler Hefti, Jacqueline, Dominique Jean, Alison Rosier, Mia Derstine, David Hillebrandt, Lenka Horakova, Linda E. Keyes, Kastė Mateikaitė-Pipirienė, Peter Paal, Marija Andjelkovic, Beth Beidlemann, and Susi Kriemler. High-altitude pulmonary edema in women: a scoping review-UIAA Medical Commission Recommendations. High Alt Med Biol. 24:268-273, 2023. Background: High-altitude pulmonary edema (HAPE) can occur >2,500-3,000 m asl and is a life-threatening medical condition. This scoping review aims to summarize the current data on sex differences in HAPE. Methods: The International Climbing and Mountaineering Federation (UIAA) Medical Commission convened an international author team to review women's health issues at high altitude. Pertinent literature from PubMed and Cochrane was identified by keyword search combinations (including HAPE), with additional publications found by hand search. The primary search focus was for original articles that included minimum one woman and at least a rudimentary subgroup analysis. Results: The literature search yielded 7,165 articles, 416 of which were relevant for HAPE, and 7 of which were ultimately included here. Six were case series, consistently reporting a lower HAPE prevalence in women. The one retrospective case-control study reported male HAPE prevalence at 10/100,000 and female at 0.74/100,000. No studies were identified that directly compared sex differences in the prevalence of HAPE. No published data was found for topics other than epidemiology. Conclusions: Few studies and associated methodological limitations allow few conclusions to be drawn. Incidence of HAPE may be lower in women than in men. We speculate that besides physiological aspects, behavioral differences may contribute to this potential sex difference.