Findings of Cognitive Impairment at High Altitude: Relationships to Acetazolamide Use and Acute Mountain Sickness

Phillips, Lara, Buddha Basnyat, Yuchiao Chang, Erik R. Swenson, and N. Stuart Harris. Findings of cognitive impairment at high altitude: relationships to acetazolamide use and acute mountain sickness. High Alt Med Biol. 18:121-127, 2017. Objective: Acute mountain sickness (AMS) is defined by patient-reported symptoms using the Lake Louise Score (LLS), which provides limited insight into any possible underlying central nervous system (CNS) dysfunction. Some evidence suggests AMS might coexist with altered neural functioning. Cognitive impairment (CI) may go undetected unless a sensitive test is applied. Our hypothesis was that a standardized test for mild CI would provide an objective measure of CNS dysfunction, which may correlate with the symptoms of AMS and so provide a potential new tool to better characterize altitude-related CNS dysfunction. We compared a cognitive screening tool with the LLS to see if it correlated with CNS dysfunction. Methods: Adult native English-speaking subjects visiting Himalayan Rescue Association aid stations in Nepal at 3520m (11,548ft) and 4550m (14,927ft) were recruited. Subjects were administered the LLS and a slightly modified version of the environmental Quick mild cognitive impairment screen (eQmci). Medication use for altitude illness was recorded. Scores were compared using the Spearman's correlation coefficient. Data also included medication use. Results: Seventy-nine subjects were enrolled. A cut-off of three or greater was used for the LLS to diagnose AMS and 67 or less for the eQmci to diagnose CI. There were 22 (28%) subjects who met criteria for AMS and 17 (22%) subjects who met criteria for CI. There was a weak correlation (r(2)=0.06, p=0.04) between eQmci score and LLS. In matched subjects with identical LLS, recent acetazolamide use was associated with significantly more CI. Conclusion: Field assessment of CI using a rapid standardized tool demonstrated that a substantial number of subjects were found to have mild CI following rapid ascent to 3520-4550m (11,548-14,927ft). The weak correlation between the LLS and eQmci suggests that AMS does not result in CI. Use of acetazolamide appears to be associated with CI at all levels of AMS severity.