Plasma high-density lipoprotein cholesterol responses to endurance exercise training: A meta-analysis of randomized controlled trials

Abstract

Background: Endurance exercise improves lipid and lipoproteins levels, while low high-density lipoprotein cholesterol (HDL-C) levels are risk factors for cardiovascular disease. There is a lack of evidence for the exercise characteristics in increasing lipids level, irrespective of the fact that endurance exercise increases lipids and lipoproteins level. The aim of this study was to clarify the effect and characteristics of endurance exercise in increasing HDL-C in randomized controlled trials. Methods: A search was performed for published studies between 1999 and 2014. Studies that assessed endurance exercise for ≥8 weeks and also reported the HDL-C levels pre- and post-training were included. The random effects model was used to measure the association between exercise and net change of HDL-C. Univariate regression analyses investigated the correlation of exercise characteristics. Subgroup and sensitivity analyses were performed to explore the sources of heterogeneity and the effect of potential confounders. The influence of pre-exercise lipid profile was assessed by meta-regression. Data were analyzed using Stata SE (12.0). Results: Fourteen studies with a total of 777 subjects were included. The mean HDL-C was reported to be increased and was statistically significant (weighted mean difference: 4.41 mg/dL; 95% confidence interval [CI]: 2.16–6.66 mg/dL, P < 0.001; I2 = 87.4%, P < 0.001). Univariate analysis indicated that exercise length was significantly associated with a net change of HDL-C (r = 0.56, P = 0.01). Nevertheless, there was no significant association between exercise frequency, duration, and total minutes. By subgroup analysis, exercise increased HDL-C level in Asia, Europe, and Africa and among all body mass index groups (P < 0.05). None of the studies omitted, in turn, seemed to substantially influence the effect of exercise on HDL-C by sensitivity analysis. Meta-regression showed that pre-exercise total cholesterol (TC) negatively correlated with net change of HDL-C (95% CI: 0.127, −0.018, r = −0073, P = 0.012). However, pre-exercise triglycerides, low-density lipoprotein cholesterol, and HDL-C did not correlate with a net change of HDL-C. Conclusions: Regular endurance exercise increases HDL-C level in any weight population. Exercise length of more than 8 weeks was the most important element of an exercise prescription. Among all lipid profiles, only the initial lower TC level responded better to exercise training and was more effective in increasing HDL-C level.