Blunted Autonomic Response To Orthostasis In Individuals With Intellectual Disabilities Compared To Controls

Abstract

Individuals with intellectual disabilities (ID) have limited cardiorespiratory capacity, not explained by lack of motivation or lack of understanding the testing procedures. Previous research suggests these limits in cardiorespiratory capacity may be due to autonomic dysfunction in individuals with ID, but this has not been tested. PURPOSE: To compare the autonomic response to standing up (a basic clinical autonomic function test) of individuals with ID to a control group without ID. METHODS: Thirteen individuals with ID and 12 individuals without ID were instrumented with an ECG-lead and finger-plethysmography for continuous heart rate and blood pressure recordings. After resting supine they moved to a standing position and returned to the supine position, each for 10 min. The last five minutes of every position was used to calculate time-domain and frequency-domain heart rate variability and blood pressure variability measures, common non-invasive indices of autonomic function. RESULTS: Individuals with ID showed different responses compared to individuals without ID for R-R-interval (RRI), root mean square of successive differences (RMSSD), the proportion of times the change in consecutive intervals exceeds 50 milliseconds (pNN50), power in the high frequency of heart rate variability (RRI HF), spontaneous baroreflex sensitivity (sBRS) and power in the low frequency of blood pressure variability (SAP LF) (p<0.05; Table). CONCLUSIONS: These preliminary results suggest a blunted response to standing up in individuals with ID, but our findings need to be confirmed with a larger sample.