Effects of Aging and Physical Activity on Cardiovascular Responses to Acute, Induced Inflammation

Background: Aging is characterized by increased arterial and ventricular stiffness and systemic inflammation. This leads to a concomitant rise in both arterial elastance (Ea: total arterial load) and ventricular elastance (Elv: left ventricular contractility or stiffness). Their ratio (Ea/Elv) determines ejection fraction. Co-morbidities common in aged individuals transiently cause further up-regulation of inflammation. This may predispose older adults to cardiac events. Physically active older adults, however, retain a more compliant cardiovascular system, partially mediated by reduced systemic inflammation. Purpose and Hypothesis: This study investigated the effects of acute inflammation on cardiovascular (Ea and Elv), and endothelial function and blood pressure, in older versus younger adults. The association of physical activity and inflammation-induced cardiovascular changes were investigated. We hypothesized increased Ea/Elv that would be greater in older versus younger adults. We hypothesized that younger adults would have a larger decrement in endothelial function and lesser increase in blood pressure versus older adults, but that physical activity would protect both groups from these changes. Methods: End-systolic and central blood pressure were obtained using applanation tonometry before and at 24 and 48 hr after an influenza vaccination. Ultrasonography was used to measure cardiac volumes and other indices of performance. Ea=end-systolic pressure (ESP)/ stroke volume and Elv=ESP/end-systolic volume. Endothelial function was assessed using flow-mediated dilation. Physical activity was measured with accelerometry. Results: There was no change in Ea or Ea/Elv (p>0.05), but a reduction in Elv (p<0.05) in both older and younger adults. Systolic performance was reduced in older but not younger adults, while diastolic performance was attenuated in both groups at 24 hr post-inflammation (p<0.05 for all). Younger adults attenuated flow-mediated dilation at 24 and 48 hr post-inflammation and older adults did not, (p<0.05). Older adults decreased peripheral and central systolic pressure after inflammation, and younger adults did not, (p<0.05). Physical activity intensity was inversely related to the change in Elv at 24 hr post-vaccination, p<0.05. Conclusion: Aging does not affect the elastance response but does affect the blood pressure and endothelial responses to acute, induced inflammation. Physical activity was inversely related to the change in Elv following acute inflammation.