Domain Specific Changes in Cognition at High Altitude and Its Correlation with Hyperhomocysteinemia

Abstract

Though acute exposure to hypobaric hypoxia is reported to impair cognitive performance, the effects of prolonged exposure on different cognitive domains have been less studied. The present study aimed at investigating the time dependent changes in cognitive performance on prolonged stay at high altitude and its correlation with electroencephalogram (EEG) and plasma homocysteine. The study was conducted on 761 male volunteers of 25–35 years age who had never been to high altitude and baseline data pertaining to domain specific cognitive performance, EEG and homocysteine was acquired at altitude ≤240 m mean sea level (MSL). The volunteers were inducted to an altitude of 4200–4600 m MSL and longitudinal follow-ups were conducted at durations of 03, 12 and 18 months. Neuropsychological assessment was performed for mild cognitive impairment (MCI), attention, information processing rate, visuo-spatial cognition and executive functioning. Total homocysteine (tHcy), vitamin B12 and folic acid were estimated. Mini Mental State Examination (MMSE) showed temporal increase in the percentage prevalence of MCI from 8.17% on 03 months of stay at high altitude to 18.54% on 18 months of stay. Impairment in visuo-spatial executive, attention, delayed recall and procedural memory related cognitive domains were detected following prolonged stay in high altitude. Increase in alpha wave amplitude in the T3, T4 and C3 regions was observed during the follow-ups which was inversely correlated (r = −0.68) to MMSE scores. The tHcy increased proportionately with duration of stay at high altitude and was correlated with MCI. No change in vitamin B12 and folic acid was observed. Our findings suggest that cognitive impairment is progressively associated with duration of stay at high altitude and is correlated with elevated tHcy in the plasma. Moreover, progressive MCI at high altitude occurs despite acclimatization and is independent of vitamin B12 and folic acid.

Homocysteine and cognition: A systematic review of 111 studies

“…Interestingly, Sharma et al, 2014, found that the plasma Hcy levels increased proportionately with the duration of stay at high altitude and hypobaric hypoxia. Moreover, the Hcy levels were inversely correlated with the MMSE scores during across the entire follow-up period(137). Moreover, the study of deWhalley et al, 2014, supported an association between HHcy and late onset dementia during a five-year follow-up.…”

“…Nevertheless,Ganguli et al, 2014, found no associations between the Hcy levels and cognitive functions during transverse analyses but there was a significant association between the Hcy levels and the executive function domain during four years of follow-up(135). In addition, five studies demonstrated a significant association between the plasma Hcy levels and cognitive function during some point of the longitudinal design(136)(137)(138)(139)(140). Hence, Van den Kommer and colleagues showed that higher Hcy levels at baseline were negatively associated with prolonged lower cognitive function and a faster rate of decline in information processing speed and fluid intelligence(140).…”

The Impact of Different Environmental Conditions on Cognitive Function: A Focused Review

“…Alternatively, the cognitive deficits suffered during chronic high altitude exposure may be due to hyperhomocysteinemia . Elevated circulating levels of homocysteine have been associated with declines in cognitive function in several geriatric population based studies (Wright et al, 2004 ), and there is a strong correlation between homocysteine in plasma and cognitive impairment during chronic (18 months) hypoxia exposure (Sharma et al, 2014 ). Interestingly, this study further supports the notion that altitude acclimatization does not induce a favorable adaptation with regards to cognitive function.…”

Phenolic Acids-Rich Fractions from Agaricus bitorguis (Quél.) Sacc. Chaidam ZJU-CDMA-12 Mycelia Modulate Hypoxic Stress on Hypoxia-Damaged PC12 Cells

“…Especially, hypoxia in high altitude continuously affects physical and mental performances and it is known to cause cognitive and mental dysfunctions such as memory deficits, motor impairment, and hypophagia [ 39 , 40 ]. Diverse arrays of physiological and psychological responses are instigated by the unique physical and environmental factors of cold arid high-altitude regions of the world [ 41 ]. The plateau is characterized by chillness and oxygen shortage.…”