Diabetes Duration, Cholesterol Levels, and Risk of Cardiovascular Diseases in Individuals With Type 2 Diabetes

Objective. To investigate the association of diabetes duration with cardiovascular disease (CVD) risk and to examine the relationship between lipid levels and CVD risk over the duration. Methods. Using the Korean National Health Insurance Service Cohort database, we identified 2 359 243 subjects with type 2 diabetes aged ≥ 20 years in 2015 to 2016. Baseline lipid levels and diabetes duration were evaluated and followed up until December 2020 (mean follow-up, 3.9 years). Subjects were categorized according to diabetes duration (new-onset, < 5 years, 5-9 years, or ≥ 10 years). We analyzed the new-onset diabetes group with low-density lipoprotein cholesterol (LDL-C) < 70 mg/dL as the reference group. The hazard ratios (HRs) and 95% CIs of myocardial infarction (MI) and ischemic stroke (IS) were estimated using a Cox proportional hazards model adjusted for potential confounders. Results. During follow-up, 45 883 cases of MI and 53 538 cases of IS were identified. The risk of MI or IS began to increase at LDL-C ≥ 160 mg/dL in the new-onset diabetes group, and at LDL-C ≥ 130 mg/dL in the group with diabetes duration < 5 years. Among subjects with diabetes duration of 5 to 9 years, LDL-C levels of 100-129 mg/dL, 130-159 mg/dL, and ≥ 160 mg/dL were significantly associated with the risk of MI (HR [95% CI] 1.13 [1.04-1.22], 1.28 [1.17-1.39], and 1.58 [1.42-1.76], respectively). MI risk in the diabetes duration ≥ 10 years group was increased by 16%, even in the LDL-C 70-99 mg/dL population (HR [95% CI] 1.16 [1.08-1.25]). Conclusion. This population-based longitudinal study revealed that the LDL-C cutoff level for increasing the risk of CVD varied with diabetes duration and that the target LDL-C level should depend on the duration.