Genetic susceptibility to dyslipidemia and incidence of cardiovascular disease depending on a diet quality index in the Malmö Diet and Cancer cohort

BACKGROUND: By taking diet quality into account, we may clarify the relationship between genetically elevated triglycerides (TG) and low-density lipoprotein-cholesterol (LDL-C), and better understand the inconsistent results regarding genetically elevated high-density lipoprotein-cholesterol (HDL-C), and cardiovascular disease (CVD) risk. METHODS: We included 24,799 participants (62 % women, age 44–74 years) from the Malmö Diet and Cancer cohort. During a mean follow-up time of 15 years, 3068 incident CVD cases (1814 coronary and 1254 ischemic stroke) were identified. Genetic risk scores (GRSs) were constructed by combining 80 validated genetic variants associated with higher TG and LDL-C or lower HDL-C. The participants’ dietary intake, assessed by a modified diet history method, was ranked according to a diet quality index that included six dietary components: saturated fat, polyunsaturated fat, fish, fiber, fruit and vegetables, and sucrose. RESULTS: The GRS(LDL-C) (P = 5 × 10(−6)) and GRS(HDL-C) (P = 0.02) but not GRS(TG) (P = 0.08) were significantly associated with CVD risk. No significant interaction between the GRSs and diet quality was observed on CVD risk (P > 0.39). A high compared to a low diet quality attenuated the association between GRS(LDL-C) and the risk of incident ischemic stroke (P interaction = 0.01). CONCLUSION: We found some evidence of an interaction between diet quality and GRS(LDL-C) on ischemic stroke. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12263-016-0536-0) contains supplementary material, which is available to authorized users.