Background: Studies reported that lipid-lowering treatment may increase the risk of diabetes, support the hypothesis that low-density lipoprotein cholesterol (LDLC) may be associated with type 2 diabetes (T2D).

Objective: The aim of this study was to assess the association between the LDLC levels and the incidence of T2D in an Iranian high-risk population not treated with lipid-lowering medications.

Methods: Mean 10-year follow-up data (1819) in non-diabetic first-degree relatives (FDR) of consecutive patients with T2D 30-70 years old, who were not treated with lipid-lowering drugs at baseline were examined. The diagnosis of T2D based on serial oral glucose tolerance test was the primary outcome. Cox proportional hazard model was used to estimate the hazard ratio (HR) for the incidence of T2D within tertiles of LDLC.

Results: A higher LDLC concentration was significantly associated with higher risk of T2D. Compared with the first tertile, the adjusted risk of T2D increased for the second (HR 1.20, 95% CI: 1.07, 1.35, P < 0.01) and third (HR 1.22, 95% CI: 1.08, 1.37, P < 0.01), tertiles of LDLC.

Conclusions: While these results await confirmation, a higher LDLC level was significantly associated with higher risk of T2D, independent of age, gender, fasting plasma glucose, waist circumference or blood pressure, in high-risk individuals in Iran.