Incidence of Mild Cognitive Impairment with Ascending Altitude.

This study aimed to longitudinally quantify the prevalence of mild cognitive impairment (MCI) in individual trekkers at three different ascending altitudes (Site 1: ∼3500 m, Site 2: ∼4400 m, and Site 3: ∼5100 m). We correlated these findings with the presence of acute mountain sickness (AMS). We performed serial assays using the environmental quick mild cognitive impairment (eQMCI) score on 103 English-speaking 18- to 65-year-old volunteers trekking to Everest Base Camp in Nepal during spring 2016. We defined MCI as a score less than 67 (lower scores indicating more cognitive impairment). Additional data collected included the Lake Louise Score, demographics, and other possible confounders. eQMCI scores significantly decreased with ascent from Site 1 to 2 (a score of 78.95 [SD = 7.96] to 74.67 [SD = 8.8] [Site 1-2  = 0.04]), but then increased on ascent to Site 3 to 83.68 (SD = 8.67) (Site 1-3  = <0.0001, Site 2-3  = <0.0001). However, subjects who fulfilled eQMCI criteria for MCI increased despite the overall improvement in score: 6.8% ( = 7) at Site 1, 18.7% ( = 14) at Site 2, and 3.3% ( = 2) at Site 3. Incidence of AMS at Sites 1, 2, and 3 was 22.3% ( = 23), 21.3% ( = 16), and 48.3% ( = 29), respectively. Of those with MCI, 1.94% met criteria for AMS at Site 1 ( = 0.0017), 2.67% at Site 2 ( = 0.6949), and 3.33% at Site 3 ( = <0.0001). There is a significant incidence of MCI at high altitude, even in those without subjective findings of AMS. Interestingly, subjects with a decline in cognitive function show an increasing trend for developing AMS at higher altitude. Future research on the clinical impact of MCI on a subject's health, judgment, and performance remains to be elucidated.