Effects of plasma lipids and smoking on cognitive function

Aim: To research the relations between plasma lipids and smoking as they affect cognitive functions. Some studies have suggested a relationship between plasma cholesterol concentration, smoking, and the frequency of cognitive disturbances. Our hypothesis was that plasma lipids and smoking are related to cognitive impairment. Materials and methods: The plasma lipid profiles and cognitive functions of the subjects were measured and the relations among plasma lipid levels, smoking, and cognitive functions were observed. The study was performed on subjects with no history of chronic disease. Mental status was evaluated by the mini-mental state examination (MMSE) in patients over 40 years of age at the Family Medicine Clinic. In the statistical analyses, Mann-Whitney U, logistic regression, Pearson correlation, and factorial ANOVA tests were used. Results: Increased total cholesterol (TC), low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), and low-density to high-density lipid ratios (LDL/HDL) were associated with reduced mental test scores, while high-density lipoprotein (HDL) levels were correlated with improved cognitive function. The negative relation between LDL and cognitive function was more relevant in smokers. Age was negatively related in both genders, whereas educational status was positively related, particularly in women. There was a negative correlation between LDL and language scores on the MMSE and this relation was more relevant in smokers. The mean LDL and LDL/HDL scores of the "24 points and lower" group for total MMSE scores were statistically higher than those of the "over 24" group. Conclusion: We concluded that for individuals with higher TC, VLDL, LDL, and LDL/HDL ratio levels and/or lower HDL levels, mental functions should be followed carefully, especially in smokers.