New-onset seizure at high altitude among healthy males

The risk of developing new-onset seizure following ascent to high-altitude areas is currently unknown. We undertook a prospective study to quantify this risk.

The study was conducted at a tertiary care hospital in India between July 2015 and December 2017. It included apparently healthy males of age ≥18 years who ascended to an altitude of ≥ 2500 m and stayed there for > 30 continuous days. Individuals with a history of seizure in the past two years, those who had not undergone acclimatization protocol, and those who had a history of any chronic systemic illness were excluded.

The 39,213 individuals included in the study together had 39,848.6 person-years of high-altitude exposure. New-onset seizure after ascent occurred in 41 of them, indicating a seizure incidence rate of 102.9 per 100,000 person-years (95% CI = 75.8-139.7). The incidence per 100,000 person-years (95% CI) at altitudes of 2,500-3,500 m, 3,500-5,800 m, and > 5,800 m was 82.3 (53.6-126.1), 134.6 (84.9-213.6), and 210.8 (52.8-841.4), respectively. Seizure was secondary to cerebral venous thrombosis in 12 (29.3%) individuals. No etiology could be determined in the remaining 29 (70.7%) individuals.

Our findings suggest that when subjects living at sea level are exposed to high altitudes, they will be at a higher risk for new-onset seizure in the immediate few months of exposure, and that this risk increases with increasing altitude.