The effect of age and lifestyle factors on plasma levels of apolipoprotein E

Background The plasma concentration of apolipoprotein E might be an important risk factor for various chronic diseases, including coronary heart disease. Objective To investigate the role of lifestyle-related factors in determining concentrations of apolipoprotein E. Methods The independent effects of age and several lifestyle-related factors [body mass index (BMI), smoking, consumption of alcohol, physical activity, educational level and poly-unsaturated:saturated fatty acid intake ratio in diet] on the apolipoprotein E concentration were assessed for a sample of 757 middle-aged working men. Multiple log-linear regression models were fitted with additional correction for the apolipoprotein E polymorphism. Results The overall mean plasma concentration of apolipoprotein E was 3.44 mg/dl with mean levels varying from 2.42 mg/dl in men with the E4/4 phenotype to 8.32 mg/dl in men in the E2/2 group. In multivariate analysis apolipoprotein E levels were found to be significantly positively correlated to BMI (P< 0.0001) and consumption of alcohol (P = 0.04). The effect of age on the apolipoprotein E concentration was significantly quadratic (P = 0.02) with highest levels found in the men aged 40-44 years (levels 13.3 % greater than those in the men aged 35-39 years). Subjects with BMI in the range 27-30 kg/m2 had on average a 16.4 % higher apolipoprotein E concentration than did men in the group with BMI lower than 23 kg/m2. This adjusted proportional increase amounted to 22.6 % for the severely obese subjects (BMI> 30 kg/m2). The independent effect of current smoking was only of borderline statistical significance. Conclusions These results indicate that age and lifestyle-related factors, such as BMI and to a lesser extent consumption of alcohol and smoking, should be taken into account as possible confounders in the study of the plasma concentration of apolipoprotein E as a risk factor for coronar