Effects of age, sex, and body mass index on sudomotor and cardiovagal functions in a healthy Korean population

Abstract

Background: Hypertension results from an impaired baroreceptor reflex and enhanced sympathetic activity. The prevalence of hypertension differs among ethnicities and is more frequent in South Asians than in Caucasians, suggesting that baseline autonomic nervous system functions and their regulation may also differ among ethnic groups. In most studies, the reference values for clinical autonomic function tests are obtained from heterogeneous ethnic populations, or ethnic factors are not considered in the study design. Obtaining reference data in a homogenous ethnic group and comparing them within various ethnic groups could be helpful to detect ethnic differences in autonomic functions. The aim of this study was to identify normative reference values for standard autonomic reflex measurements in a homogeneous Korean population. Methods: A total of 181 healthy Korean volunteers (age, 20-74 years) underwent standard autonomic function tests: heart rate difference during deep breathing, Valsalva maneuver, and the quantitative sudomotor axon-reflex test. Mean and 5th and 95th percentile values were obtained for each age group. We also analyzed factors (age, sex, and body mass index) that can influence autonomic functions. Results: The heart rate difference during deep breathing and expiratory-inspiratory ratio were higher in males than in females and were inversely related to age. The Valsalva ratio was inversely related to age. Males had higher sweat volumes at all body areas evaluated than those of females, and only forearm sweat volume was significantly different between the age groups. Conclusions: Cardiovagal function was affected by age and sex in Koreans. Sudomotor function was affected by sex, and only forearm sweat volume was affected by age and sex. These results represent preliminary normative clinical autonomic data in a Korean population comprised of a single ethnicity.