An assessment of cardiovascular and biochemical parameters in aircrew with prolonged exposure to high altitude: Nigeria as a case study

Abstract

Many factors, including tourism, migration, and business, are causing an exponential increase in the number of individuals exposed to high altitudes worldwide. About 100 million lowlanders travel to mountainous areas above 2500 m yearly, while roughly 400 million people are residents in areas above 1500 m. While highlanders suffer from the harmful impacts of high altitude, lowlanders who visit high altitudes also encounter similar disadvantages. There is evidence linking high altitude to hypoxia, hypobaria, and hypothermia. Despite conflicting information regarding the effects of high-altitude exposure on renal and hepatic damage, dyslipidemia, and insulin resistance, studies illustrating the impact of high altitude on physiological systems are available. Thus, this study aims to investigate how exposure to high altitude and associated pathways affect insulin sensitivity, gluco-lipid regulation, and renal and hepatic function in aircrew members of local airlines (PHA-L) and international airlines (PHA-I) who have been traveling for at least five years. The cross-sectional study consists of a total of 300 aviation workers assigned to 3 groups (n=100) subjects per group with a sample selection carried out using the random sampling method. An open-ended structured questionnaire was administered to the participants prior to sample collection to obtain socio demographic data. Anthropometric data including weight, height, blood pressure, waist and hip circumference, as well as biochemical parameters such as lipid profile, kidney function, and inflammatory and oxidative stress markers were determined. Participants were fasted overnight for 12 hours and then blood samples were obtained from them before analysis. The first stage of this research investigated if lowlanders who have traveled to high altitudes were more likely to develop obesity and atherogenic indices because of their high altitudes exposure. Exposure to high altitude markedly increased the incidence of obesity independent of the dietary patterns of the subjects when comparison with the control. More specifically, when compared to the control, exposure to high altitude increased the levels of serum total cholesterol, triglycerides, and low-density lipoprotein but decreased the amount of high-density lipoprotein. TNF-α and IL-1β levels were also elevated, along with higher Castelli risk indices I and II. In comparison to PHA-L, the detected disturbances in PHA-I were much higher. This study's second section looked into how exposure to high altitude affected renal function and lipid profiles. The high-altitude group showed increased triglycerides, low-density lipoprotein (LDL), very low-density lipoprotein, and atherogenic indices levels but decreased high-density lipoprotein (HDL) levels when compared to the control group. In participants exposed to high altitude, these observations were accompanied by decreased Ca2+-ATPase and Na+/K+-ATPase activities and increased serum urea, blood urea nitrogen (BUN), creatinine, C-reactive protein, TNF-α, IL-1β, and malondialdehyde. This study's third section assessed how exposure to high altitude affected liver function and insulin sensitivity. Additionally, the possible roles of inflammation, specifically, C-reactive protein (CRP), tumor necrosis factor-α (TNF- α), interleukin-1β (IL-1 β) signaling pathway and oxidative stress were evaluated in lowlanders who were high-altitude travelers. It was demonstrated that the individuals who had been exposed to high altitude had considerably lower levels of total protein and higher levels of AST, ALT, and ALP, indicating altered liver function, as compared to the control group. Furthermore, exposure to high altitudes raised insulin resistance and glucose plasma levels. In addition, when compared to the control, high altitude exposure resulted in a substantial increase in triglycerides, low-density lipoprotein (LDL), TC/high-density lipoprotein (HDL), and LDL/HDL, but a decrease in HDL levels. These events were accompanied by significant reductions in GSH level, GPx, GST, SOD, catalase, Ca2+-ATPase and Na+/K+-ATPase activities, and an increase in malondialdehyde, TNF-α, IL-1β, and C-reactive protein levels. Overall, high altitude exposure led to impaired renal and hepatic functions, insulin resistance, and dyslipidemia. These harmful effects, which were mediated by the activation of oxidative stress, and the elevation of pro-inflammatory cytokines, were much greater in PHA-I than in PHA-L.