The study team used a recently developed epidemiology tool called Mendelian randomization (MR). MR analyzes genetic variations using a method that identifies genes responsible for particular diseases, independent of confounding factors such as differences in behavior or environmental influences that often limit the conclusions of epidemiology research. This was one of the largest studies to date using MR, as well as the largest to use an allele-score method, described below.
The researchers analyzed DNA data from 17 studies including over 60,000 individuals, of whom more than 12,000 had experienced coronary heart disease, including heart attacks. Because previous studies had found signals from nearly 200 genes to be associated with blood lipid levels, the study team aggregated data into composite groups, called allele scores, for each of three blood lipids: LDL, HDL and triglycerides, then calculated their relationship to coronary heart disease.
As expected, the current study confirmed that higher levels of LDL, the "bad cholesterol," were more likely to cause heart disease. But there were new results: high levels of triglyceride also caused higher risk of heart disease. At the same time, there was little evidence that higher levels of HDL, the "good cholesterol," had a protective effect.
The novelty of their approach, say the authors, lies in their use of a gene score MR analysis using individual participant data. These results build on previous findings and help clarify in further detail the separate roles of triglycerides and HDL in risk for coronary heart disease.
Previous genetic studies, including by Keating and others, found associations among gene variations (single nucleotide polymorphisms, or SNPs) and heart disease, but did not indicate causality, as found in the c
|Contact: John Ascenzi|
Children's Hospital of Philadelphia