Background
Cardiovascular risk factors tend to aggregate. The biological and
predictive value of this aggregation is questioned and genetics could shed
light on this debate. Our aim was to reappraise the impact of risk factor
confluence on ischemic heart disease (IHD) risk by testing whether genetic
risk scores (GRSs) associated with these factors interact on an additive or
multiplicative scale, and to determine whether these interactions provide
additional value for predicting IHD risk.
Methods and Results
We selected genetic variants associated with blood pressure, body
mass index, waist circumference, triglycerides, type-2 diabetes, HDL and LDL
cholesterol, and IHD to create GRSs for each factor. We tested and
meta-analyzed the impact of additive (Synergy Index –SI–)
and multiplicative (βinteraction) interactions between
each GRS pair in one case-control (n=6,042) and four cohort studies
(n=17,794), and evaluated the predictive value of these
interactions. We observed two multiplicative interactions:
GRSLDL·GRSTriglycerides
(βinteraction=−0.096; Standard
Error=0.028) and non-pleiotropic
GRSIHD·GRSLDL
(βinteraction=0.091; Standard
Error=0.028). Inclusion of these interaction terms did not improve
predictive capacity.
Conclusions
The confluence of LDL cholesterol and triglycerides genetic risk load
has an additive effect on IHD risk. The interaction between LDL cholesterol
and IHD genetic load is more than multiplicative, supporting the hazardous
impact on atherosclerosis progression of the combination of inflammation and
increased lipid levels. The capacity of risk factor confluence to improve
IHD risk prediction is questionable. Further studies in larger samples are
warranted to confirm and expand our results.