Synergistic effect of smoking and blood pressure on augmentation index in men, but not in women.

This study was conducted in healthy Japanese subjects to examine the effects of age and gender on the relationship between the risk factors for cardiovascular disease (CVD) and augmentation index (AI), and the effects of clusters of those risk factors on AI. Radial arterial pressure wave analysis was used to obtain AI in 3675 men and 2919 women. AI was found to be higher in women than in men, and age-related increase in AI showed an attenuated curve in subjects aged >or=50 years. A step-wise multivariate linear regression analysis showed that mean blood pressure and smoking are independent significant variables related to AI in men regardless of age, and in women aged <50 years, but not in women aged >or=50 years. A general linear model univariate linear regression analysis showed that mean blood pressure and smoking had a significant interaction for their relation with AI in men, but not in women. In conclusion, among the risk factors for CVD, smoking and blood pressure were found to be independent factors related to increase in AI. Although age-related attenuation of increase in AI was confirmed in Japanese subjects, these risk factors may act to increase AI even in elderly subjects, at least in part. However, the effects of these factors on AI may differ based on gender, and these factors may act synergistically to increase AI in men. On the contrary, these factors may act independently in young women to increase AI without interaction, whereas only the blood pressure seems to increase AI in elderly women.