# Effect of chronic high-altitude exposure on postoperative pulmonary complications: a retrospective cohort study

## TL;DR

Chronic high-altitude exposure may increase the risk of postoperative pulmonary complications, according to a large retrospective study.

## Contribution

This study is one of the first to investigate the impact of chronic high-altitude exposure on postoperative pulmonary complications using a large cohort and propensity score matching.

## Key findings

- Patients with chronic high-altitude exposure had a higher incidence of postoperative pulmonary complications (5.7% vs. 4.7%).
- Propensity score matching confirmed a statistically significant association between chronic high-altitude exposure and increased odds of complications (OR 1.25).
- CHAE patients had longer hospitalization and postoperative recovery durations compared to non-exposed patients.

## Abstract

Many factors can influence the occurrence of postoperative pulmonary complications (PPCs) in the perioperative period, but it is unclear whether chronic high-altitude exposure (CHAE) affects the occurrence of PPCs.

This retrospective study included 235,128 surgical patients aged 18 years and older from January 2013 to December 2022. The occurrence of PPCs, such as pneumonia, atelectasis, and respiratory failure, was determined based on the admission and discharge diagnoses. To reduce the confounding effects caused by imbalances in demographic and clinical characteristics at baseline, we employed a 1:1 propensity score matching (PSM) to match the CHAE and non chronically high-altitude exposed (NCHAE) patients. Statistical analyses were conducted from January 1, 2025, to March 1, 2025.

A total of 235,128 cases were included, with 11,075 (4.7%) patients experiencing PPCs. There were 8,565 patients with CHAE, of whom 484 (5.7%) developed PPCs. In contrast, there were 226,562 patients NCHAE, with 10,591 (4.7%) experiencing PPCs. After 1:1 PSM, 8,564 CHAE were matched with 8,564 NCHAE. In the CHAE group, 484 (5.7%) experienced PPCs, while 394 (4.6%) in the NCHAE group shoewd a statistically significant difference (p = 0.002). Adjusted multivariable conditional logistic regression analysis indicated that CHAE increased the incidence of PPCs (odds ratio [OR], 1.25; 95% CI, 1.02–1.53). Furthermore, the length of hospitalization and postoperative hospitalization duration of patients in the CHAE group were longer than those in the NCHAE group.

This retrospective study suggests an association between CHAE and PPCs within 30 days after surgery. However, the undefined exposure duration highlight the need for prospective studies to definitively establish causality.