High density lipoprotein cholesterol increases with living altitude

Background The relationship between high density lipoprotein cholesterol (HDL) 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, district and the altitude at which they Lived were included. The factors measured included HDL, Living altitude, body mass index (BMI), smoking habits, alcohol 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 higher HDL levels than heavy or mild drinkers and non-drinkers (P < 0.01). Physical 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 between HDL and altitude persists when taking altitude as a categorical or a continuous variable. Conclusions High density lipoprotein cholesterol levels are linearly and significantly increased when living at a higher altitude. This fact should be taken into account when comparing cardiovascular risk in populations living at different altitudes.