Exploring Sympathetic Nervous System Function in Individuals With Down Syndrome

Description

Down syndrome (DS), the most common genetic cause of intellectual disability, is associated with widespread organ dysfunction, including abnormalities in the autonomic nervous system (ANS). The ANS regulates critical functions such as heart rate (HR) and blood pressure (BP), both essential for maintaining homeostasis and supporting physical activity. Individuals with DS often exhibit blunted HR responses to exercise-typically \~30 beats per minute below expected levels-suggesting reduced sympathetic nervous system (SNS) activity. The SNS governs rapid changes in HR and BP during stress by releasing catecholamines: epinephrine (from the adrenal medulla) and norepinephrine (from sympathetic nerve endings). Despite its importance, SNS function has not been comprehensively assessed among individuals with DS. This study addresses a critical knowledge gap by evaluating SNS responses to physiological stressors in individuals with DS. The investigators will measure beat-to-beat HR and BP, along with plasma catecholamine levels, in response to sympathetic activation, comparing individuals with DS to age- and sex-matched controls. Understanding the mechanisms of SNS dysfunction in DS is vital, as it likely underlies reduced exercise capacity and contributes to broader clinical challenges. These insights may guide targeted interventions to improve cardiovascular function, physical capacity, and overall quality of life in this understudied population.

Interventions

• Cold Stress (Other)
  Cold triggers the sympathetic nervous system, known as the 'fight-or-flight' response, which prepares the body to respond to a perceived threat by increasing heart rate, blood pressure, and releasing catecholamines. These measurements will be taken to examine how individuals with DS will respond during a cold stress test. The investigators are looking at how plasma catecholamines (i.e., Epinephrine, Norepinephrine, and Dopamine), blood pressure, and heart rate are expressed during a cold stress test in individuals with Down syndrome, who have proposed autonomic dysfunction. This study will compare responses among individuals with Down syndrome to a control group without Down syndrome.
• Maximal Dynamic Exercise (Other)
  The investigators are looking at how plasma catecholamines (i.e., Epinephrine, Norepinephrine, and Dopamine), blood pressure, and heart rate are expressed during a treadmill maximal exercise test in individuals with Down syndrome, who have proposed autonomic dysfunction. This study will compare responses among individuals with Down syndrome to a control group without Down syndrome.
• Isometric Handgrip Exercise with Post-Exercise Muscle Ischemia (Other)
  The investigators are looking at how plasma catecholamines (i.e., Epinephrine, Norepinephrine, and Dopamine), blood pressure, and heart rate are expressed during a isometric handgrip exercise followed by an ischemic period which will be induced by a blood pressure cuff in individuals with Down syndrome, who have proposed autonomic dysfunction. This study will compare responses among individuals with Down syndrome to a control group without Down syndrome.
• Head-up Tilt Table Test (Other)
  The investigators are looking at how plasma catecholamines (i.e., Epinephrine, Norepinephrine, and Dopamine), blood pressure, and heart rate are expressed during passive head-up tilt testing which is a standardized, noninvasive clinical and research procedure used to characterize cardiovascular autonomic responses to orthostatic stress, among individuals with Down syndrome, who have proposed autonomic dysfunction.

Eligibility criteria

Conditions

Locations

• Linda Crnic Institute for Down Syndrome, University of Colorado Anschutz Medical Campus — Aurora, Colorado, United States