Aerobic Exercise Training and Blood Lipids-Lipoproteins Among Healthy Adults: A Methodological Umbrella Review

Abstract

PURPOSE: Meta-analyses (MA) that have examined whether aerobic exercise training (AET) affects blood lipids-lipoproteins have yielded conflicting findings. Since methodological characteristics and completeness of reporting may influence interpretation and generalizability of MA results, we sought to assess the quality of these parameters in published MA that examined the blood lipids-lipoproteins response to AET. METHODS: We used search terms related to AET and blood lipids-lipoproteins in six databases to find MA published in English, Portuguese, or Spanish. The MA included trials that: (1) enrolled adults with no established disease; (2) compared AET to a non-exercising, non-dieting arm (CONTROL); and (3) measured lipids-lipoproteins pre- and post-intervention. Study selection and data coding were conducted in duplicate. Methodological quality was assessed using a modified exercise-specific version of Assessing the Methodological Quality of Systematic Reviews 2 (AMSTAR2). RESULTS: Seven MA qualified for our umbrella review, with a total of 8,721 subjects (mean 1,245.8±602.2, range 393 to 2,024). Of these, five reported the number of AET groups for lipids-lipoproteins analysis (mean 10.3±8.3, range 2 to 35). Effect sizes (ES) for AET versus CONTROL ranged from +0.9mg/dL to -8.5mg/dL for total cholesterol, 0 to +4.6mg/dL for high-density lipoprotein, 0 to -10.1mg/dL for low-density lipoprotein, and 0 to -13.7mg/dL for triglycerides. Only one of 20 items on the modified AMSTAR2 was fully satisfied by all MA which was the reporting of the Population, Intervention, Comparator, and Timing (PICOT). Meanwhile, most MA lacked a priori study design (n=6, 85.6%), failed to explore the relationship between features of the exercise interventions and ES (n=4, 57.1%), and interpreted results without discussing risk of bias (n=5, 71.4%). CONCLUSION: Overall, included MA showed low adherence to current methodological standards, which may partially explain the disparate findings of the effects of AET on blood lipids-lipoproteins. Future MA following current methodological standards that explore possible effect modifiers are needed to more precisely estimate the influence of AET on lipids-lipoproteins.