The effect of living at high altitude on carotid intima-media thickness in the elderly: a comparative study

Background Previous studies have shown that high altitude may have a protective effect on cardiovascular diseases. However, the effects of high altitude on carotid atherosclerosis have been less evidenced. Purpose To compare the effect of altitude on atherosclerosis by using carotid artery ultrasonography (CAU) findings. Material and Methods A total of 180 patients aged >60 years, who had proper recorded data of ultrasonography and blood tests, and who resided in the same city for at least five years were included. Patients with anemia, hyperlipidemia, diabetes mellitus, hypertension, and those who did not meet the inclusion criteria were excluded. Patients were divided into two groups: high altitude group (HAG) and sea level group (SLG). CAU findings of each patient-including common carotid artery intima-media thickness (CIMT) >= 1 mm and < 1 mm, internal carotid artery (ICA) stenosis rate, and plaque types-were recorded and compared between the two groups. Blood test parameters and lipid profiles were additionally recorded. Results Prevalence of patients with CIMT >= 1 mm was significantly higher in the SLG (SLG: 50%, HAG: 15.6%; P < 0.001). Carotid stenosis was found to be significantly different in both groups (HAG: 9.96% +/- 23.27%, SLG: 29.83% +/- 23.30%; P < 0.001). RBC, HGB, HDL values, and HDL/LDL ratio were found to be significantly higher in the HAG (P < 0.001) whereas LDL, TG, and TC values were significantly higher in the SLG (P < 0.001). Conclusions People who reside at high altitudes have significantly lower rate of carotid stenosis, lower CIMT values, and less atherogenic lipid profile values, all of which indicate protective effect of high altitude on atherosclerosis.