The Relationship Between Body Mass Index and Aortic Stiffness in Females Across the Lifespan

Abstract

Obesity, classified by a body mass index (BMI) >30 kg/m2, continues to be a health concern for women in the United States across all ages. Obesity is a traditional risk factor for the development of cardiovascular disease (CVD). One novel non-traditional predictor of future CVD risk is aortic stiffness. Obese individuals have increased aortic stiffness compared to those of normal body size. PURPOSE: Determine the relationship between BMI and aortic stiffness in 476 women between the ages of 9-83 years old. METHODS: Girls (n= 123, age 9-12 years (yrs), BMI 21 ± 5 g/m2), young women (n= 138, age 18-39 yrs, BMI 24.89 ± 4.46 kg/m2), middle age women (n= 137, age 40-59 yrs, BMI 26.73 ± 4.22 kg/m2) and older women (n= 78, age 60-83 yrs, BMI 26.34 ± 4.26 kg/m2) participated in the study. BMI was calculated as weight (kg) / height (m)2. Aortic stiffness was measured as carotid-femoral pulse wave velocity (PWV) using applanation tonometry (SphygmoCor; Sydney, Australia). RESULTS: According to results from linear regression, BMI was a significant predictor of PWV for the female children (β= 0.387, p<0.01, 95% CI 0.03 – 0.076), young women (β= 0.635, p<0.01, 95% CI 0.156 – 0.237) and middle age women (β= 0.508, p<0.01, 95% CI 0.113 – 0.210). BMI was not a significant predictor of PWV in the older women (β= 0.107, p= 0.20, 95% CI -0.073 – 0.178). When exploring age-group by BMI interaction terms, significant group differences were detected in the relation between BMI and PWV. Using the young women as a reference group – there was no significant difference between the slopes of the regression lines for BMI and PWV between the young and middle age women (β= -0.03, p=0.36, 95% CI -0.11 – 0.04). There were significant differences between the slopes of the regression lines between the young women and girls (β= -0.14, p<0.01, 95% CI -0.21 – -0.08) and between the young women and older women (β= -0.14, p<0.01, 95% CI -0.23 – -0.06). CONCLUSION: Our data suggest that the relationship between BMI and aortic stiffness changes with advancing age. BMI is a significant predictor of aortic stiffness in females between the ages of 9-59 yrs, but not in elderly females (>60 yrs). In older females changes in body composition (i.e. increases in body fat and decrease in muscle mass) may change the relationship between BMI and aortic stiffness. FUNDING SOURCES: NIH, DRI, AHA, ACSM