Cognitive Effects of Repeated Acute Exposure to Very High Altitude Among Altitude-Experienced Workers at 5050 m

We investigated altitude effects on different cognitive domains among perennial shift-workers at the Atacama Large Millimeter/submillimeter Array Observatory (5050 m), Chile. Twenty healthy male workers were recruited and assigned to either a moderate-altitude first (MAF group, Test 1: 2900 m and Test 2: 5050 m) or to a high-altitude first (HAF group, Test 1: 5050 m and Test 2: 2900 m). Test 1 was conducted at the beginning and Test 2 at the end of the shift-work week. Processing speed (RTI, reaction time), attention (AST, attention-switching task, and RVP, rapid visual processing), and executive function (OTS, One Touch Stockings of Cambridge) were assessed. Of the three cognitive domains assessed, only processing speed showed altitude-at-test group interaction (RTI median five choice reaction time: F_{1, 17} = 6.980, [Formula: see text] = 0.291, p = 0.017). With acclimatization, there was a decrease in AST reaction latency mean (t₁₇ = -2.155, d_z = 1.086, p = 0.046), an increase in RVP accuracy (t₁₇ = 2.733, d_z = 1.398, p = 0.014), and a decrease in OTS mean latency first choice (t₁₇ = -2.375, d_z = 1.211, p = 0.03). Decreased variability in cognitive function was observed in AST reaction latency standard deviation (t₁₇ = -2.524, d_z = 1.282, p = 0.022) and in RVP response latency standard deviation (t₁₇ = -2.35, d_z = 1.177, p = 0.03) with acclimatization. At 5050 m of elevation, SpO₂ was positively correlated with executive function in the MAF group (OTS problems solved on first choice: r₍₅₎ = 0.839, p = 0.018) and negatively correlated with executive function latency standard deviations in the HAF group (OTS latency to first choice standard deviation: r₍₁₀₎ = -0.618, p = 0.032). Our findings highlight the importance of acclimatization and improvement of blood oxygen level, even among high altitude-experienced workers, to optimize performance of cognitively demanding work and reduce high altitude-associated health risks.