Threshold Effects in the Relationship Between Serum Non-High-Density Lipoprotein Cholesterol and Metabolic Syndrome

BACKGROUND: Previous studies have suggested that the non-high-density lipoprotein cholesterol (non-HDL-C) is strongly associated with metabolic syndrome (MetS); however, the explicit relationship between them has not yet been clarified. The aim of this study was to reveal the explicit association between the non-HDL-C with MetS. METHODS: The present study was based on a cross-sectional study, which was carried out in Spain. A total of 60,799 workers were recruited between 2012 and 2016. Anthropometric parameters and blood indices (lipid profile and fasting blood glucose) were collected. Participants were divided into the MetS group or the non-MetS group based on the criteria of the National Cholesterol Education Program Adult Treatment Panel III. The relationship between serum non-HDL-C and the risk of MetS was evaluated using multivariate regression analysis, piece-wise linear regression analysis, smooth curve fitting and threshold saturation effect analysis after adjustment of potential confounders. RESULTS: The risk of developing MetS increased with increasing non-HDL-C level. However, this association was only presented in the range of the non-HDL-C concentrations from 118 mg/dl to 247 mg/dl after adjusting for potential confounders. When compared to lower non-HDL-C level (<118 mg/dl), higher levels of non-HDL-C (118–247 mg/dl and >247 mg/dl) were related to higher incidence of MetS, with adjusted odds ratio (95% confidence interval) of 3.08 (2.77, 3.42) and 17.18 (14.29, 20.65), respectively (P for trend <0.05). CONCLUSION: Higher serum non-HDL-C level was associated with increased MetS incidence; however, significant threshold saturation effects were observed when the non-HDL-C level <118 mg/dl or >247 mg/dl.