LDL cholesterol level as a risk factor for retinopathy and nephropathy in children and adults with type 1 diabetes mellitus: A nationwide cohort study

BACKGROUND: Microvascular complications are common in people with diabetes, where poor glycaemic control is the major contributor. The aim of this study was to explore the association between elevated LDL cholesterol levels and the risk of retinopathy or nephropathy in young individuals with type 1 diabetes. METHODS: This was a nationwide observational population‐based cohort study, including all children and adults with a duration of type 1 diabetes of ≤ 10 years, identified in the Swedish National Diabetes Register between 1998 and 2017. We calculated the crude incidence rates with 95% confidence intervals (CIs) and used multivariable Cox regression to estimate crude and adjusted hazard ratios (HRs) of retinopathy or nephropathy in four LDL cholesterol categories: <2.6 (Reference), 2.6–3.4, 3.4–4.1 and > 4.1 mmol L(−1). RESULTS: In total, 11 024/12 350 (retinopathy/nephropathy, both cohorts, respectively) children and adults (median age 21 years, female 42%) were followed up to 28 years from diagnosis until end of study. Median duration of diabetes when entering the study was 6 and 7 years in the retinopathy and nephropathy cohort, respectively. Median LDL cholesterol was 2.4 mmol L(−1), and median HbA1c level was 61 mmol mol(−1) (7.7 %). After multivariable adjustment, the HRs (95% CI) for retinopathy in individuals with LDL cholesterol levels of 2.6–3.4, 3.4–4.1 or > 4.1 mmol L(−1) were as follows: 1.13 (1.03–1.23), 1.16 (1.02–1.32) and 1.18 (0.99–1.41), compared with the reference. The corresponding numbers for nephropathy were as follows: 1.15 (0.96–1.32), 1.30 (1.03–1.65) and 1.41 (1.06–1.89). CONCLUSIONS: Young individuals with type 1 diabetes exposed to high LDL cholesterol levels have an increased risk of retinopathy and nephropathy independent of glycaemia and other identified risk factors for vascular complications.