Cardiovascular Autonomic Function and HRV in Healthy Adults of Rajasthan: A Cross-sectional Study on the Influence of Age and Gender

Background Heart rate variability (HRV) and cardiovascular autonomic reflex tests (CARTs) serve as non-invasive clinical indicators of central autonomic network function and cardiovagal regulation. Purpose This study aimed to establish regional normative reference values for HRV and CART parameters in healthy adults from northwestern India to evaluate the modulating effects of age, biological sex and subclinical cardiometabolic risk factors. Methods This cross-sectional study evaluated 142 healthy subjects (74 males, 68 females) aged 18–70 years. Baseline vital signs and time-domain HRV parameters (standard deviation of normal-to-normal intervals (SDNN) and root mean square of successive differences (RMSSD)) were recorded. Autonomic reactivity was assessed using deep breathing (expiration-to-inspiration (E:I) ratio), the Valsalva manoeuvre, isometric handgrip and orthostatic challenge. A high-risk sub-cohort ( n = 21) with subclinical obesity or elevated blood pressure was analysed. Adherence to Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines was maintained. Results The total study sample comprised 142 participants, including 74 males (52.1%) and 68 females (47.9%). The high-risk subset comprised 11 males (52.4%) and 10 females (47.6%). Resting heart rate was higher in females (74.6 ± 8.2 bpm) than in males (70.1 ± 7.6 bpm; t (140) = 3.39, p = .02), while blood pressure was higher in males ( p = .03). Time-domain HRV and reflex indices declined significantly with age ( p < .001), with optimal thresholds for autonomic senescence occurring at 47 years (SDNN, area under the curve (AUC) = 0.82) and 49 years (Valsalva, AUC = 0.79). Healthy females exhibited enhanced cardiovagal responses (E:I, Valsalva and 30:15 ratios; p < .05). This female autonomic advantage was entirely blunted in the high-risk subset ( n = 21), where autonomic parameters fell below the 5th percentile limits (SDNN = 25 ms, RMSSD = 18 ms, Valsalva ratio = 1.09). Conclusion Healthy adults exhibit an age-related decline in parasympathetic function and a female-specific cardiovagal advantage. Subclinical cardiometabolic risk factors override these physiological buffers, blunting gender-related protection and accelerating autonomic senescence.