Introduction:
Physical activity is presumed to improve cardiovascular disease (CVD), of which carotid artery intima-media thickness (CIMT) is a common indicator. Individuals with spinal cord injury (SCI) have limited mobility and therefore an expected increased risk for CVD. The purpose of this study was to determine which CVD risk factors predict CIMT among women with SCI, with the ultimate goal of targeting therapy to improve CVD in this population.
Methods:
One hundred twenty-two women with SCI who attended an outpatient SCI clinic and met inclusion and exclusion criteria participated in this study. SCI was categorized into 1 of 4 categories: complete tetraplegia, incomplete tetraplegia, complete paraplegia, and incomplete paraplegia. Maximum heart rate and VO2 max were obtained using bicycle ergometry with ventilatory gas exchange and continuous electrocardiogram. Hierarchical regression was used to predict CIMT, with the first block including demographic variables (age, race, smoking status) and the second block including physiologic variables (total cholesterol, heart rate, VO2 max, BMI, fasting serum glucose, hemoglobin A1c, and blood pressure).
Results:
Similar findings were observed for left and right CIMT, therefore only results from right CIMT are reported. The overall model was significant, F(16,46)=8.53, p=.000. Adjusted R square was .54 for the first block of variables and increased significantly (p=.006) to .66 when the second block of variables was added. Significant predictors at alpha=.05 included age (beta=.51, t=4.79, p=.000) and max/peak heart rate (beta=−.336, t=−2.39, p=.02). At alpha=.10, A1c was significant (beta=.187, t=1.99, p=.053).
Conclusions:
Although low aerobic conditioning is a purported CVD risk factor, quantitative measurements of such lack a demonstrable relationship with subclinical atherosclerosis (CIMT), perhaps because of its reduced importance relative to other CVD risk factors in a mobile population. We found expected relationships with CIMT in our SCI population (i.e., age), however we also found a quantitative measure of aerobic conditioning (max/peak heart rate) to be associated with CIMT. Our data indicate that SCI individuals may bear a greater CVD burden from cardiac de-conditioning than the general population and that investigation of a cohort with mobility limitation may provide a unique opportunity to study the impact of physical conditioning on CVD risk.
Post-exercise heart rate recovery in individuals with spinal cord injury
