Relationship between atherogenic index of plasma with trajectory and risk of Cardio-cerebral vascular diseases in middle-aged and elderly people: a national cohort study

Objective This study aims to explore the relationship between the plasma atherosclerotic index (AIP) and its changing trend and the risk of cardiovascular and cerebrovascular diseases (CCVD) in middle-aged and elderly people. Methods The study encompassed 7,137 participants aged 45 years and over who took part in the China Health and Retirement Longitudinal Study (CHARLS) from 2011 to 2020.Through different grouping methods in two phases, the Cox proportional hazards model was used and multiple confounding factors were adjusted. To evaluate the relationship between the AIP index and its changing trend and the risk of CCVD onset, smooth curve fitting and threshold effect analysis were applied to explore the nonlinear relationship between the AIP index and the cumulative AIP index and the risk of CCVD onset. Result Of the 7,131 participants, 2,037 participants experienced CCVD events in phases1. Compared with the T1, after adjusting for all confounding factors, for every one-unit increase in the AIP index in T3, the CCVD risk was 27.0% (HR 1.270, 95% CI 1.134–1.423, P < 0.001). Curve fitting and threshold effect analysis indicated that there were significant nonlinear relationships between the AIP index and cumulative AIP and the risk of CCVD. The interaction of subgroup analysis showed that there might be differences in the association between AIP and its trajectories and the risk of cardiovascular and cerebrovascular diseases in both male and female populations (P < 0.05).Of the 3,958 participants, 878 participants experienced CCVD events in phases2. Longitudinal analysis of AIP changes revealed that, relative to the stable low-risk group (Class 1), the risk of CCVD increased by 25.2% in Class 2, 20.7% in Class 3, and 23.3% in Class 4. The stratified analysis revealed that among men, those in class 4 had a significantly increased risk of cardiovascular and cerebrovascular diseases by 69.6%, while among women, only class 2 showed a marginally significant increase in risk 19.4%.No significant relationship was found between AIP and the risk of cardiovascular and cerebrovascular diseases in the female population. Among postmenopausal women, those whose AIP index rose rapidly within three years had a 65.9% higher risk of cardiovascular and cerebrovascular diseases (P < 0.05). Conclusion The dynamic trajectory of the plasma atherosclerosis index (AIP) can accurately identify individuals at high risk of cardiovascular and cerebrovascular diseases. Especially, men with persistently high AIP and women with rapid increase in AIP before menopause are of particular concern. The menstrual status is an important factor influencing lipid levels in women. The AIP index and its dynamic change trend can be used as important indicators for evaluating the risk of CCVD.