NIRS Based Measures Of Reactive Hyperemia Do Not Reflect Differences In Arterial Age Of Adults

Improved detection of diseases remains a public health priority. Microvascular function (e.g., reactive hyperemia [RH]) is a known predictor of cardiovascular disease. Other approaches include characterizing the age of the macrovascular system via arterial stiffness (e.g., pulse wave velocity [PWV]) and blood pressure (BP). No previous study has evaluated differences in near-infrared spectroscopy (NIRS) based measures of RH between individuals with healthy and unhealthy arterial age. PURPOSE: We aimed to test for group differences between adults exhibiting older and younger arterial ages compared to their chronological age. METHODS: One hundred and four adults were evaluated for arterial age, estimated based on PWV and BP. The sample was dichotomized into groups exhibiting older or younger arterial age compared to their chronological age. Each participant completed a vascular occlusion test consisting of 3 minutes of baseline, 5 minutes of ischemia, and 3 minutes of reperfusion. Skeletal muscle tissue oxygenation (StO2) was collected from the forearm flexor muscle group. The first 10 seconds of reperfusion (upslope) and the maximal StO2 (StO2max) were calculated. We have shown that upslope and StO2max represent different underlying physiology; thus, these measures provided a comprehensive overview of RH. Analysis of covariance (ANCOVA) models were used to test for differences in NIRS outcomes. A p ≤ 0.05 was considered significant. RESULTS: The younger arterial age group (n = 69) exhibited a mean of 17 ± 11 yrs younger than their chronological age, whereas the other group (n = 35) was 8 ± 5 yrs older than their chronological age. The young arterial age group was chronologically younger than the other group (33 ± 15 vs. 53 ± 18 yr; p < 0.001). The ANCOVA (covariate: chronological age) for upslope indicated no difference (p = 0.978) in the adjusted means (1.96 ± 0.76 vs.1.87 ± 0.83%·s-1). For StO2max, the ANCOVA indicated no difference (p = 0.129) between the adjusted means (79.5 ± 4.4 vs. 83.2 ± 3.8%). CONCLUSION: Despite a difference in the macrovasculature, the groups did not differ in microvascular function. Perhaps arterial aging detects changes in health sooner than NIRS-based RH measures. However, future studies are needed to understand further the ability of macro- and microvasculature to predict disease onset.