Spotlight on Hypertension: Harnessing Functional Near-Infrared Spectroscopy to Track Microvascular Health in Women
Madhusudhan Umesh, Kalpana Medala, Golla Vahini, Vidya SingaraveluObjectives:
Hypertension (HTN) is a prevalent cardiovascular disorder known to adversely affect microvascular function, leading to impaired vasodilation, altered blood flow regulation, and progression of vascular as well as cognitive disorders. These subtle microvascular alterations often remain undetected, particularly in women, who may present with different vascular responses compared to men. Functional near-infrared spectroscopy (fNIRS) is a non-invasive neuroimaging technique that measures changes in oxygenated (HbO 2 ) and deoxygenated hemoglobin (HbR), thereby providing insight into both cerebral and peripheral hemodynamic responses. The present study aimed to evaluate the utility of fNIRS in detecting microvascular dysfunction among hypertensive women.
Materials and Methods:
A cross-sectional comparative study was conducted following institutional ethical approval. Twenty women diagnosed with primary HTN and twenty normotensive age-matched normotensives were recruited. fNIRS recordings of HbO 2 and HbR concentrations were obtained at rest, during a 10-min mild-to-moderate exercise protocol, and in the recovery period. Data were analyzed using independent Student’s t -tests for pairwise baseline comparisons. To account for repeated measures across time points (rest, activity, post-activity), longitudinal linear mixed-effects models were conducted with Group, Time, and Group × Time interaction terms as fixed effects and subject identity as a random intercept (alpha = 0.05).
Results:
Hypertensive participants (mean age 44.2 ± 8.52 years) demonstrated significantly higher mean arterial pressure (116.75 ± 4.92; p < 0.005) compared with normotensives. Baseline (0.26 ± 0.12 vs. 0.57 ± 0.41) and activity-phase (0.91 ± 0.26 vs. 1.89 ± 1.31) HbO 2 values were significantly lower in hypertensive women ( p < 0.005). Post-exercise HbO 2 levels were also lower but did not reach statistical significance. Similarly, baseline (0.23 ± 0.25 vs. 0.73 ± 0.51), activity (0.64 ± 0.06 vs. 1.15 ± 1.33), and post-activity (0.30 ± 0.15 vs. 0.62 ± 0.44) HbR levels were significantly reduced ( p < 0.005).
Conclusion:
In this short cross-sectional study, fNIRS showed preliminary sensitivity in detecting changed cerebral hemodynamic profiles in hypertensive women under physical stress. While these preliminary data indicate that fNIRS may be useful as an exploratory research tool for detecting neurovascular changes, bigger prospective longitudinal trials are required to determine its true clinical utility and predictive significance.