Associations between serum lipid levels and cognitive impairment in hypertensive patients: a case-control study

OBJECTIVE: Previous studies have shown that lower serum lipid levels are associated with the development of cognitive impairment (CI), dementia, and Alzheimer's disease. However, the relationship between serum lipid levels and CI in hypertensive patients has not been determined. This case-control study aimed to investigate the relationship between serum lipid levels and CI in hypertensive patients. METHODS: A total of 1840 hypertensive patients (age: 69.70 ± 6.07; sex: male: 908/49.35%) were enrolled in this study, including 460 hypertensive patients with CI and 1380 hypertensive patients with normal cognitive function matched 1:3 by age and sex. The cognitive function and sleep quality of hypertensive patients were assessed using the Mini-mental State Examination (MMSE) and Pittsburgh Sleep Quality Index (PSQI). The relationship between serum lipid levels and CI in hypertensive patients was analyzed using multifactorial logistic regression. Spearman's correlation coefficient was used to analyze the correlation of serum lipid levels with MMSE scores and PSQI total scores in hypertensive patients. RESULTS: After adjusting for all factors, serum low-density lipoprotein cholesterol (LDL-C) levels were negatively correlated with CI in hypertensive patients (OR = 0.823, 95%CI: 0.729-0.928, P = 0.001), and this association remained significant in patients with at least a junior high school education (OR = 0.727, 95%CI: 0.592-0.894, P = 0.002). However, serum total cholesterol (TC) and triglyceride (TG) levels were not correlated with CI in patients with hypertension (P > 0.05). In addition, serum LDL-C levels were positively correlated with MMSE total score (r = 0.139, P < 0.001), orientation (r = 0.118, P < 0.001), memory (r = 0.057, P = 0.014), attention and numeracy (r = 0.091, P < 0.001), recall ability (r = 0.065, P = 0.005), and language ability (r = 0.107, P < 0.030); serum TG, TC, and LDL-C levels were negatively correlated with PSQI total score (r = - 0.051, P = 0.029; r = - 0.090, P < 0.001; r = - 0.082, P < 0.001). CONCLUSION: Lower serum LDL-C levels are associated with CI in hypertensive patients. Although causality cannot be inferred, findings suggest that LDL-C may be a relevant biomarker in cognitive screening. Therefore, serum lipid levels should be reasonably controlled according to their individual conditions.