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Updated: Apr 27, 2026
Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance
Published on: March 21, 2013
Normal HR with tilt, yet autonomic dysfunction in persons with Down syndrome
Kanokwan Bunsawat1, Styliani Goulopoulou, Scott R Collier
11Integrative Physiology Laboratory, Department of Kinesiology and Nutrition, University of Illinois, Chicago, IL; 2Department of Physiology, Georgia Regents University, Augusta, GA; 3Department of Health, Leisure, and Exercise Science, Appalachian State University, Boone, NC; 4Department of Nutrition, Food, and Exercise Sciences, Florida State University, Tallahassee, FL; and 5Department of Physical Therapy, Wichita State University, Wichita, KS.
Insights
Individuals with Down syndrome (DS) show reduced sympathetic nervous system activity during upright tilt, even when heart rate responses are matched. This suggests altered autonomic function in DS persists despite similar cardiovascular adjustments.
Area of Science:
- Cardiovascular Physiology
- Autonomic Nervous System Function
- Down Syndrome Research
Background:
- Individuals with Down syndrome (DS) exhibit distinct autonomic nervous system (ANS) function at rest and during adrenergic stimulation.
- Previous research indicates altered autonomic responses in DS, but a detailed comparison of heart rate variability (HRV) during orthostatic stress is lacking.
- Understanding these autonomic differences is crucial for managing cardiovascular health in persons with DS.
Purpose of the Study:
- To compare cardiac autonomic function between individuals with and without DS during upright tilt using HRV analysis.
- To investigate if HRV responses during tilt differ in persons with DS, particularly when matched for heart rate (HR) changes.
- To elucidate the sympathetic and parasympathetic nervous system balance during orthostatic challenge in DS.
Main Methods:
- A case-control study involving 15 individuals with DS and 15 age- and sex-matched controls.
- Participants underwent a 5-minute passive upright tilt at 80°. A subset of individuals with DS (n=11) were not matched for HR response.
- Heart rate variability (HRV) was analyzed in both time (RMSSD) and frequency domains (LnLF, LnHF, LF/HF ratio, TP) before and during tilt.
Main Results:
- While HR changes were similar in DS-matched and control groups, they were lower in the unmatched DS group.
- Both DS groups showed a reduction in low-frequency power (LnLF), indicating altered sympathetic activity, unlike the control group.
- The increase in the LF/HF ratio, a marker of sympathetic dominance, was attenuated in the unmatched DS group compared to controls.
Conclusions:
- Despite similar heart rate responses to upright tilt in matched groups, individuals with Down syndrome demonstrate reduced sympathetic nervous system dominance.
- These findings highlight persistent alterations in autonomic cardiovascular regulation in persons with DS during orthostatic stress.
- Further research is warranted to explore the clinical implications of these autonomic differences in the DS population.
Unlabelled:
Persons with Down syndrome (DS) exhibit altered autonomic function at rest and in response to adrenergic stimuli. It is unknown whether a subset of persons with DS that have similar HR responses to a task would have similar responses in HR variability (HRV).
Purpose:
This study aimed to compare cardiac autonomic function during upright tilt using HRV analysis in persons with and without DS when persons with and without DS were matched for the change in HR.
Methods:
Persons with (25 ± 2 yr; 30.4 ± 1.9 kg·m, n = 15) and without DS (27 ± 2 yr; 24.7 ± 1.1 kg·m, n = 15) were matched on their HR response to a 5-min tilt at 80°, whereas a subset of persons with DS (28 ± 3 yr; 33.5 ± 2.0 kg·m, n = 11) were not matched for the change in HR. HRV was assessed in both the frequency (natural log transformation (Ln) of low frequency (LF), high frequency (HF), LF/HF ratio, and total power (TP)) and time domains (root mean square of successive differences [RMSSD]).
Results:
Changes in HR were similar in DS-matched and control but lower in DS-not matched. Tilt effects were observed for LnHF, LNTP, and RMSSD in all groups (P < 0.05). Both groups of persons with DS exhibited reduction in LnLF, with no change in the control group (P < 0.05). The increase in LF/HF was greater in the group without DS when compared with that in DS-not matched (8.71 ± 2.38 vs 2.34 ± 1.39, P < 0.05) but not when compared with that in DS-matched (3.59 ± 1.10, P = 0.075).
Conclusions:
Despite similar HR response to passive upright tilt in the DS-matched, we still observed reduced sympathetic dominance in response to upright tilt in persons with DS.
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