How five months in Tibet changed the heart and lungs of Beijing workers

By Hugo Francisco de SouzaReviewed by Susha Cheriyedath, M.Sc.Jul 13 2025

Even the healthiest lowlanders aren’t immune: five months at 3,700 meters led to measurable drops in aerobic capacity and heart-lung function, sounding a warning for those planning extended stays in high-altitude environments.

Study: Effects of long-term very high-altitude exposure on cardiopulmonary function of healthy adults in plain areas. Image Credit: Flystock / Shutterstock

In a recent study published in the journal Scientific Reports, researchers conducted an observational study to evaluate the impacts of high-altitude (HA) exposure (particularly long-term) on human cardiopulmonary function.

The study focused on data from 45 healthy participants from Beijing, China (plains area ~40 m elevation) working/living for five months in Lhasa (HA ~3,700 m elevation) before returning to their low elevation homes.

Cardiopulmonary exercise testing (CPET) and a plethora of other physiological and pulmonary function tests revealed that long-term HA exposure imposed significant functional decline in cardiopulmonary performance on the otherwise visibly healthy study participants, with nine CPET indicators across respiratory, metabolic, and circulatory function exhibiting measurable declines.

This study highlights the hidden costs of long-term HA living, especially for individuals not habituated to the environment.

The authors emphasize that these results reflect functional changes, not necessarily permanent or structural damage, and further research is needed to determine the duration and reversibility of these effects.

Background

High-altitude (HA) environments are known to present a cocktail of physiological challenges to humans, including low oxygen pressure, extreme dryness, solar radiation exposure, and freezing temperatures. However, their long-term impacts on physiological biomarkers remain poorly understood.

Scientists believe that while native populations may adapt genetically and physiologically to the harsh demands of HA life, lowlanders, even healthy ones, may not be so lucky.

Previous research suggests that hypobaric hypoxia, a condition resulting from the physiological toll of low barometric pressure alongside low atmospheric oxygen, may trigger cardiopulmonary remodeling, HA-associated hypertension, and an observable drop in exercise tolerance that may persist even after the subject returns to the plains.

Unfortunately, these reports are rare, methodologically distinct, and often provide conflicting outcomes, requiring a reassessment of the potentially hidden costs of HA life for the unprepared (non-acclimatized) lowlander.

Understanding the physiological toll of prolonged altitude exposure is critical, especially as more lowland people travel or relocate to mountainous regions for work or relaxation.

This research will help inform potential movers, as well as public health professionals, of the risks of HA living and the means by which they can minimize their exposure and potential adverse outcomes.

About the study

The present study aims to provide this increasingly imperative information by carrying out an in-depth pre-and post-observational study on 45 lowland healthy participants (about 13% female; mean age ≈ 41 years) who relocated to a HA environment for five months.

Participants were screened to only include individuals from Beijing, China (low lying, ~40 m above sea level) without a history of cardiopulmonary disease and no previous long-term HA exposure. All participants were subjected to experimental assays twice, before and after their five-month stay at Lhasa (HA region, ~3,700 m above sea level).

Assays included: 1. Anthropometric and clinical assessments such as weight, waist/hip circumference, oxygen saturation (SpO₂), blood pressure, and body mass index (BMI), 2. Static pulmonary function tests to assess lung volume and airflow using the COSMED Quark PFT Ergo system, and 3. Cardiopulmonary exercise testing (CPET).

CPET is the current gold standard non-invasive assay for elucidating patients’ whole-body oxygen metabolism and exercise performance via combinations of blood pressure monitoring, breath-by-breath gas analysis, and a 12-lead electrocardiogram (ECG).

For the present study, researchers measured peak oxygen uptake (VO₂ peak), peak cardiac output (CO_peak), oxygen uptake efficiency slope (OUES), and anaerobic threshold (AT).

Study findings

The present study revealed a significant, detrimental, and statistically significant drop in aerobic capacity and cardiopulmonary efficiency observed after five months of HA exposure, despite no observable changes in lung capacity or overall body weight. In particular, VO₂ peak was observed to decline from 29.46 ± 6.95 to 23.33 ± 4.71 mL/kg/min (p < 0.001), indicating impaired maximal aerobic function.

AT and CO_peak demonstrated similar declines, with reductions of about 24% and about 20% respectively, suggesting exacerbated fatigue onset and impaired circulatory function. The OUES efficiency slope also significantly decreased (indicative of hampered ventilatory efficiency) alongside a notable increase (25.62 to 27.57 [p = 0.004]) in the slope of minute ventilation and carbon dioxide production (VE/VCO₂ slope; measure of ventilatory inefficiency).

Together, these findings identify reduced lung perfusion and ventilatory efficiency as a consequence of prolonged unacclimatized HA exposure.

The study captured the body’s compensatory response to chronic hypoxia, as demonstrated by a slight drop in SpO₂ (-0.8%) and a corresponding increase in systolic and diastolic blood pressure. Finally, as static lung function remained unchanged before and after HA exposure, HA’s impacts are likely circulatory and metabolic rather than structural.

The authors suggest these changes may relate to increased pulmonary artery pressure, vascular remodeling, and alterations in myocardial and metabolic function, though further mechanistic studies are needed.

Importantly, the study notes that most declines were “functional,” meaning participants’ physiological performance on exercise testing worsened, but there was no evidence of overt structural lung injury.

Conclusions

The present study provides compelling evidence cautioning lowlanders with little to no HA preparation of the subtle but measurable deterioration in cardiopulmonary function after long-term exposure to very high altitudes.

While structural lung metrics remained intact, aerobic efficiency, circulatory dynamics, and metabolic responses declined, suggesting that prolonged hypobaric hypoxia can overwhelm compensatory mechanisms over time.

Clinical interventions should recommend tailored endurance training and periodic medical monitoring for travellers planning extended high-altitude stays, and cardiopulmonary rehabilitation or gradual altitude re-adaptation upon lowlanders’ return to sea level.

Limitations

The authors note several significant limitations: the study included a relatively small, homogeneous sample (predominantly male, Chinese, and white-collar workers), so findings may not apply to other populations or those with different genetic backgrounds or health profiles. Individual risk factors such as smoking and drinking were not assessed.

Additionally, all tests were non-invasive, so changes in blood parameters (e.g., hemoglobin, red cell mass) were not measured. Further research is needed to confirm these findings and clarify underlying mechanisms.