ABSTRACT
Background & objectives: Ascent to high altitude has been reported to cause hippocampal atrophy and cognitive impairment in mountaineers. We assessed the cognitive performance and probable occurrence of mild cognitive impairment (MCI) in acclimatized lowlanders (ALL) staying at altitudes above 4,300 m for duration above 12 months and validated a multi-domain cognitive screening test (MDCST) for future demographic studies on MCI. Methods: Following evaluation of sensitivity and correlation of the newly developed MDCST battery with Mini Mental State Examination (MMSE) and Clinical Dementia Rating (CDR) scores on a group of 28 individuals, the MDCST battery was validated on a population of 843 ALL staying at high altitude MSL >4,300 m and 862 subjects staying at MSL <230 m. EEG recordings were performed on 840 ALL staying at altitudes above 4,300 m and 743 control subjects staying at MSL <230 m. Results: Percentage prevalence of MCI was 4.18 per cent in the ALL population as assessed by MMSE while that of the LL population was <0.42 per cent. The percentage prevalence of MCI based on calculations from the MDCST scores was 12.4 per cent in the ALL population as compared to 1.19 per cent in the LL population. Decrease in alpha wave amplitude at the T3 and T4 sources in MCI subjects was observed in LL group while there was an increase in amplitude for alpha wave in these regions in the ALL groups. Domain specific MDCST showed decline in immediate recall, procedural memory and mind body co-ordination which was negligible in the LL population. Interpretation & conclusions: MDCST exhibited excellent psychometric properties in terms of sensitivity, and test-retest reliability qualifying it to be used as a more effective cognitive measure for assessment of MCI in demographic studies in comparison to traditional measures. Our findings also showed increased prevalence of MCI in ALL population staying for longer durations at high altitude which is neurophysiologically distinct from MCI leading to Alzheimer's disease.