Abstract
INTRODUCTION: Cholesterol is an irreplaceable nutrient in pulmonary metabolism; however, studies on high-density lipoprotein cholesterol (HDL-C) levels have shown conflicting results regarding lung function. Therefore, we investigated the association between lung function and HDL-C levels in three cross-sectional studies conducted in the USA and South Korea. METHODS: US National Health and Nutrition Examination Survey (NHANES) III, US NHANES 2007-2012, and Korea National Health and Nutrition Examination Survey (KNHANES) IV-VII performed spirometry and met the American Thoracic Society recommendations. Multiple linear regression models were used to determine the relationship between serum lipid levels and lung function. The models were adjusted for age, sex, household income, body mass index, smoking pack year, use of lipid-lowering medication and race. Serum HDL-C levels were classified into three groups to assess the dose-response relationship according to the guideline from the National Cholesterol Education Program-Adult Treatment Panel III. RESULTS: The adult participants of the KNHANES (n=31 288), NHANES III (n=12 182) and NHANES 2007-2012 (n=9122) were analysed. Multivariate linear regression analysis of the serum cholesterol profiles revealed that only serum HDL-C was associated with forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV(1)) in all three studies. A 1 SD increase in the HDL-C level increased the percent predicted FVC by 0.5%-1.5% p, and the per cent predicted FEV(1) by 0.5%-1.7% p. In terms of HDL-C levels, correlations between the HDL-C groups and the per cent predicted FVC and FEV(1) showed dose-response relationships. Compared with the normal group, high HDL-C levels increased FVC by 0.75%-1.79% p and FEV(1) by 0.55%-1.90% p, while low levels led to 0.74%-2.19% p and 0.86%-2.68% p reductions in FVC and FEV(1), respectively. Subgroup analyses revealed weaker associations in females from KNHANES and NHANES III. CONCLUSION: In the three nationwide cross-sectional studies, high HDL-C levels were associated with improved FVC and FEV(1). However, future studies are needed to confirm this correlation and elucidate the underlying mechanisms.