Non-linear association between the plasma atherogenic index and type 2 diabetes mellitus: findings from a multicentre prospective cohort study based on the 4C study

Background Currently, the plasma atherogenic index (AIP) is mainly used to predict atherosclerosis and cardiovascular diseases, but there is still insufficient evidence to indicate its association with type 2 diabetes. Therefore, we aim to investigate the potential association between AIP and type 2 diabetes through a prospective cohort study. Methods The 4C study, a multicenter prospective cohort investigation, targets the Chinese population and initially enrolled 10,008 participants. Baseline data encompassing lifestyle, metabolic status, and various other factors were collected in 2011. A 10-year follow-up survey was subsequently conducted, ultimately including 9,092 participants. AIP, defined as the logarithmic transformation of the triglycerides to high-density lipoprotein ratio, was divided into quartiles. Type 2 diabetes was diagnosed following the 2013 American Diabetes Association guidelines. To explore the potential association between AIP and the risk of type 2 diabetes, Cox regression, restricted cubic spline, and subgroup analysis were employed. Results Over a 10-year follow-up period, 693 new cases of type 2 diabetes were identified. In a fully adjusted model accounting for age, sex, DBP, SBP, LDL-C, TC, Cr, FBG, HbA1c, smoking, alcohol consumption, and education level, AIP demonstrated a positive association with type 2 diabetes (HR: 4.40; 95% CI: 3.21, 6.04). Compared to the Q1 group, the risk of type 2 diabetes increased progressively across the Q2, Q3, and Q4 groups, with a significant trend (p-value < 0.05). Restricted cubic spline (RCS) analysis revealed an inverse L-shaped association between AIP and the risk of type 2 diabetes, with a turning point at 0.45. Furthermore, similar patterns were observed in the subgroup analyses, with no significant interaction between AIP and subgroup variables. Conclusions Among the Chinese population, elevated AIP levels are positively correlated with an increased risk of type 2 diabetes, indicating that AIP could potentially serve as a biomarker for assessing the risk of developing type 2 diabetes.