Association between LDL-C/HDL-C ratio and long-term carotid plaque risk in middle-aged and elderly rural populations: a prospective population study

Background Atherosclerotic cardiovascular and cerebrovascular diseases are still the main cause of global incidence rate and mortality. The LDL-C/HDL-C ratio (LHR) has been identified as a potential biomarker for cardiovascular risk. However, the relationship between it and the long-term risk of carotid plaques is not yet clear, especially in low-income populations in China. Methods This prospective cohort study included adults aged ≥45 years without carotid plaque at baseline from low-income rural areas of Tianjin, China. Baseline characteristics were collected in 2014, and follow-up data were obtained in 2019. The primary outcome was the development of new carotid plaques, assessed using carotid ultrasound. The relationship between the LDL-C/HDL-C ratio (LHR) and new carotid plaques was analyzed using multifactorial logistic regression, with the presence or absence of new-onset plaques as the dependent variable. Additionally, we utilized restricted cubic spline (RCS) regression to visually present the potential nonlinear relationship between LHR and the risk of carotid plaque. Results Over the six-year follow-up period, 606 participants (38.3%) developed new carotid plaques. Higher LHR was significantly associated with an increased risk of new carotid plaques, with each unit increase in LHR corresponding to a 35.9% higher risk (OR = 1.359, 95% CI: 1.180–1.566, p < 0.001). The RCS curve indicated a non-linear positive association between LHR and the likelihood of carotid plaques ( p for non-linearity = 0.019), with an optimal cut-off at 1.257. Logistic regression analysis confirmed that LHR > 1.257 was linked to increased odds of carotid plaques in both unadjusted (OR: 1.80, p < 0.001) and adjusted models (OR: 1.835, p < 0.001), with LHR ≤ 1.257 serving as the reference. In subgroup analysis, all subgroups consistently demonstrated a significant association between increased LHR (all OR > 1). Conclusion The research results indicate that there is a non-linear positive correlation between LHR and the long-term risk of carotid plaques in middle-aged and elderly populations, suggesting that LHR may be an effective indicator for screening carotid plaques in grassroots middle-aged and elderly populations.