Background/aims To assess changes in optic nerve sheath diameter (ONSD) at high altitude and in acute mountain sickness (AMS).
Methods Cochrane Library, EMBASE, Google Scholar and PubMed were searched for articles published from their inception to 31st of July 2020. Outcome measures were mean changes of ONSD at high altitude and difference in ONSD change between subjects with and without AMS. Meta-regressions were conducted to investigate the relation of ONSD change to altitude and time spent at that altitude.
Results Eight studies with 248 participants comparing ONSD from sea level to high altitude, and five studies with 454 participants comparing subjects with or without AMS, were included. ONSD increased by 0.14 mm per 1000 m after adjustment for time (95% CI: 0.10 to 0.18; p<0.01). Restricted cubic spline regression revealed an almost linear relation between ONSD change and time within 2 days. ONSD was greater in subjects with AMS (mean difference=0.47; 95% CI: 0.14 to 0.80; p=0.01; I2=89.4%).
Conclusion Our analysis shows that ONSD changes correlate with altitude and tend to increase in subjects with AMS. Small study number and high heterogeneity are the limitations of our study. Further large prospective studies are required to verify our findings.
- optic nerve
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T-YT and GG contributed equally.
Contributors T-YT, GG and Y-KT—study conception and design. T-YT, GG, Y-CS and Y-KT—acquisition of data. T-YT, Y-CS, Y-KL and Y-KT—analysis and interpretation of data. T-YT, GG and Y-KT—preparation of the manuscript. T-YT, GG, Y-CS, Y-KL and Y-KT—critical revisions. All authors have read and approved the final version of the manuscript for publication.
Funding This work was partly supported by research grants from the Ministry of Science & Technology in Taiwan (grant number: MOST 109-2314-B-002-150-MY3).
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval The Institutional Review Board of Dalin Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, Taiwan, approved the protocol (No. B10704012).
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement All data relevant to the study are included in the article or uploaded as supplemental information.
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