Establishment of Normative Data for Autonomic Function Tests in Indian Population

Background: Normative data for autonomic function tests (AFT) is not available for Indian population.

Objective: The aim of the study was to establish normative data in AFT and its correlation with age, gender, and body mass index.

Material and methods: The study was done on 254 healthy subjects of age ≥18 years. All AFTs were done in autonomic laboratory at the Department of Neurology, Christian Medical College and Hospital, Ludhiana. Cardiovascular tests (heart rate response to deep breathing, HR changes in Valsalva maneuver and head-up tilt test (HUT)) and quantitative sudomotor axon reflex testing (QSART) were performed in all the subjects. Fifty subjects underwent thermoregulatory sweat test (TST).

Results: The mean age (SD) of study participants was 43 (16.0) years (range 20-84), and 129 (50.8%) were men. The normative value range (2.5-97.5 percentile) for HR difference, E: I ratio, and Valsalva ratio (VR) was 3.5-47.0, 1.05-1.93, and 1.11-2.64, respectively, for all the subjects. HR difference and E: I ratio showed an significant inverse relation with age (r = -0.623 and r = -0.584, respectively). VR also showed an inverse relation with age (r = -0.575, P =< 0.001), and female had a lower value than male (1.63 vs 1.78, P =< 0.001). In QSART, mean (SD) sweat volume was higher in males 0.630 (0.230) compared to females 0.513 (0.132) for all sites, P < 0.001, and similar trend was noticed for sweat area in TST.

Discussion and conclusion: Normative AFT data has been established for Indian population for the first time. The values are comparable to previously published studies.