High density lipoprotein cholesterol increases with living altitude

Background The relationship between high density lipoprotein cholesterol (H DL) serum level and the altitude at which people live is controversial. Methods A cross-sectional study was carried out in the adult population (30 -64 years) of the Island of El Hierro (Canary Islands, Spain). In all, 594 individuals representative of the El Hierro population for gender, age, dis trict and the altitude at which they Lived were included. The factors measu red included HDL, Living altitude, body mass index (BMI), smoking habits, a lcohol consumption, diabetes, menopause in women, and physical activity and dietary habits. Results The HDL showed a correlation with living altitude (r = 0.14) P<0.01 ) and with BMI (r = -0.19, P < 0.01). Smokers had lower HDL levels than ex- smokers and non-smokers (P < 0.05). Men who were moderate drinkers had high er HDL levels than heavy or mild drinkers and non-drinkers (P < 0.01). Phys ical activity was only related to HDL in men with levels >1.52 mmol/l, who walked on the average more than the rest (P < 0.05). Variables not showing the expected relationship with HDL were diabetes and the menopause in women (probably due to a low statistical power of their subsamples). Regression analysis, with HDL as dependent variable showed that the association betwee n HDL and altitude persists when taking altitude as a categorical or a cont inuous variable. Conclusions High density lipoprotein cholesterol levels are linearly and si gnificantly increased when living at a higher altitude. This fact should be taken into account when comparing cardiovascular risk in populations livin g at different altitudes.