Evaluation of sympathetic sudomotor responses to auditory stimuli in children with autism spectrum disorders.

AIM AND OBJECTIVE: Autism spectrum disorder (ASD) being a complex neurological and developmental disorder is also associated with autonomic nervous system dysfunction. Sudomotor nerve function is one highly sensitive index of sympathetic cholinergic activity and can be evaluated by measuring sympathetic skin response (SSR) to various stimuli. Studies reporting SSR to auditory stimulus among ASDs are limited and to the extent of our knowledge not assessed in the Indian scenario. The objective of the study was to assess and compare sympathetic sudomotor activity by evaluating SSR to auditory stimuli in children with and without ASDs. MATERIALS AND METHODS: A total of eighty individuals were enrolled in the study, including forty children with ASD and forty typically developing (TD) children. SSR to auditory stimulus was assessed using a digitized data acquisition unit in a soundproof room, maintained at 23°C. SSR indices such as latent period (s), amplitude (mv), and habituation were analyzed and compared using appropriate statistical tests between the groups. P < 0.05 was considered statistically significant. RESULTS: Habituation for SSR was statistically significantly lower (P < 0.001) in children with ASD (0.43 [0.21, 0.61]) compared to TD children (0.78 [0.65, 0.95]). Latent period was also statistically significantly higher in children with ASD (1.67 [1.37, 2.02]) compared to TD children (1.41 [1.2, 1.72]). However, there was no significant difference in amplitude values between the groups. CONCLUSIONS: Children with ASDs exhibited slower habituation of SSR to auditory stimuli compared to healthy controls. This slower habituation process might be due to the persistent predominant state of sympathetic nerves, which, in turn, contributes to the atypical emotional and behavioral traits prevailing in ASDs.

Comparison of Physiological and Biochemical Autonomic Indices in Children with and without Autism Spectrum Disorders.

Background and objectives: Autism Spectrum Disorder (ASD) is a complex neuro-developmental disorder and it has been suggested that symptoms of ASD are associated with neural networks that regulate the Autonomic Nervous System (ANS). However, the nature of autonomic atypicalities in ASDs remain largely unknown. Measures like Heart Rate Variability (HRV) and urinary Vanillylmandelic Acid (VMA) estimation are sensitive and non-invasive physiological and biochemical indicators of autonomic nervous activity. This study aimed to compare the physiological and biochemical autonomic indices in children with and without ASD. Materials and Methods: In this case-control study, 40 children with autism and 40 Typically Developing (TD) children were recruited. Measures of physiological autonomic index were assessed by the analysis of short term HRV, and the urinary levels of VMA estimation was used as a biochemical autonomic index. Results: Cardiac sympathetic activity assessed by Low Frequency (nu) of HRV was significantly higher in the ASD group in comparison with the TD group (p = 0.006). On the contrary, both the High Frequency (abs) and (nu) of HRV were found to be significantly lower in autistic children (p = 0.034 and p = 0.000) than controls. Autistic children also exhibited a significantly higher level (p = 0.049) of VMA concentration compared to TD children. Conclusion: The study concludes that children with ASD exhibit lower cardio-vagal activity as measured by HRV and increased sympathetic activity as assessed by urinary VMA compared to that of TD children. The core autistic symptoms exhibited by children with ASD could be due to the differences in baseline arousal or stress which might be associated with autonomic dysfunction. Further studies are needed to examine the association of this autonomic dysregulation with ASD symptoms and comorbidities.

Electrodermal response to auditory stimuli in relation to menopausal transition period.

BACKGROUND: Menopause-associated estrogen deficiency results in climacteric symptoms like vasomotor, psychological and sleep disturbances that cause a decline in the quality of life. Electrodermal activity (EDA), a psychophysiological measure, reflects sympathetic activity, which provides information associated with individual's emotions, phobias, arousal, cognition and stress. The study compared electrodermal response to auditory stimuli between postmenopausal and perimenopausal women with and without symptoms and also correlated the association of scores of the menopausal transition symptoms with indices of EDA. METHODS: Seventy-five women volunteers in the age group of 45-60 years, 25 in each group who were postmenopausal, perimenopausal with symptoms and perimenopausal without symptoms, were recruited. Indices of EDA such as latency, amplitude, rise time and half recovery time for auditory stimuli were quantified using standard techniques. Symptoms of menopausal transition were assessed using Women Health Questionnaire. RESULTS: Analysis using one-way analysis of covariance after controlling for variables showed that mean skin conductance level of EDA was significantly higher among perimenopausal women with symptoms compared with perimenopausal women without symptoms and postmenopausal women. Perimenopausal women with symptoms had significantly lower latency of response when compared with other groups. Analysis using Pearson correlation test showed that latency of EDA had significant positive correlation and amplitude had significant negative correlation with menopausal transition symptom scores. CONCLUSIONS: Perimenopausal women with symptoms exhibited increased sympathetic sudomotor activity when compared with perimenopausal women without symptoms and postmenopausal women as measured by EDA. Further, select measures of EDA exhibited significant association with the symptoms of menopausal transition.

Assessment of Risk Factor for Cardiovascular Disease Using Heart Rate Variability in Postmenopausal Women: A Comparative Study between Urban and Rural Indian Women.

Cardiovascular diseases are important causes of morbidity and mortality in postmenopausal women. A major determinant of cardiovascular health is the status of autonomic nervous system and assessment of Heart Rate Variability (HRV). Heart Rate Variability is a noninvasive and sensitive technique to evaluate cardiovascular autonomic control. Reduced HRV is an independent risk factor for the development of heart disease. This study evaluated the risk factors for cardiovascular diseases using HRV, between urban and rural Indian postmenopausal women ranging in age from 40 to 75 years. Findings of the analysis of HRV have showed that the total power which reflects overall modulation of cardiac autonomic activity (759 ± 100 versus 444 ± 65), the absolute power of high frequency which is surrogate of cardiovagal activity (247 ± 41 versus 163 ± 45), and low frequency that reflects cardiac sympathetic activity (205 ± 26 versus 127 ± 18) were significantly higher in urban women than that of their rural counterparts. Further, among the anthropometric measures, waist circumference was significantly correlated with indices of HRV. The study concludes that rural Indian women are associated with an additional risk beyond that of ageing and postmenopausal status when compared to the urban women. The higher central obesity could be the contributing factor for developing higher risk for cardiovascular disease among the rural women.