Cardiovascular Outcomes in Patients with Both Diabetes and Phenotypic Familial Hypercholesterolemia: A Nationwide Register-Based Cohort Study

Objective Patients with diabetes or familial hypercholesterolemia (FH) have an increased incidence of cardiovascular diseases compared to the population, but whether this risk is exacerbated in patients with combined traits is unknown. Research Design and Methods In this Swedish nationwide, register-based cohort study, patients with diabetes were included between 2002 and 2020. Adjusted Cox-proportional hazards models were used to assess the risk of cardiovascular events in patients with or without phenotypic FH (≥6 points for phenotypic FH according to Dutch Lipid Clinic Network criteria) compared to general population controls without diabetes as reference. Results A total of 45,585 patients with type 1 diabetes (227,923 controls) and 655,250 patients with type 2 diabetes (655,250 controls) were followed for a median of 14.1 and 7.9 years, respectively. Of those, 153 and 7197, respectively, had phenotypic FH. Compared to controls, patients with diabetes and phenotypic FH had higher risk of cardiovascular mortality (type 1: hazard ratio 21.3, 95% confidence interval 14.6–31.0; type 2: 2.40, 2.19–2.63) and of a cardiovascular event (type 1: 15.1, 11.1–20.5; type 2: 2.73, 2.58–2.89). Further, patients with diabetes and phenotypic FH had higher LDL cholesterol levels during observation (p<0.05) and increased risk of all major cardiovascular outcomes (p<0.0001) than patients with diabetes but without FH. The proportion receiving lipid-lowering treatment, was higher in patients with phenotypic FH (p<0.0001). Conclusions Patients with both diabetes and phenotypic FH are more at risk of adverse cardiovascular outcomes and have higher LDL cholesterol levels despite receiving intensified lipid-lowering therapy.