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.
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Seated Baseline Concentration of Plasma Catecholamines
Timeframe: Seated baseline blood draw, prior to stressors
Concentration of Plasma Catecholamines During Cold Pressor Test
Timeframe: During the cold stress test, around or up to 5 minutes
Baseline Standing Concentration of Plasma Catecholamines
Timeframe: Standing baseline blood draws, prior to fear simulation
First Fear Simulation, Concentration of Plasma Catecholamines
Timeframe: During the first virtual reality fear stressor, around 5 minutes
Second Fear Simulation, Concentration of Plasma Catecholamines
Timeframe: During the second fear simulation, around 15 minutes into the test
First Minute of Pain Patch, Concentration of Plasma Catecholamines
Timeframe: Blood draw will take place within 1-minute of the application of the pain patch.
15 Minutes into Pain Patch Application, Concentration of Plasma Catecholamines
Timeframe: Blood draw will occur about 15 minutes after the application of the pain patch.
12-Hour Fast, Concentration of Plasma Catecholamines
Timeframe: Blood draw will occur following a 12-hour fast inducing hypoglycemia
Seated Baseline Blood Draw, Concentration of Plasma Catecholamines
Timeframe: Blood draw will occur prior to ingestion of caffeine pill
30 Minutes Following Ingestion of Caffeine Pill(s), Concentration of Plasma Catecholamines
Timeframe: Blood draw will occur around 30 minutes following participant ingestion of caffeine pill(s)
60 Minutes Following Ingestion of Caffeine Pill(s), Concentration of Plasma Catecholamines
Timeframe: Blood draw will occur around 60 minutes following participant ingestion of caffeine pill(s)
Baseline Standing Concentration of Plasma Catecholamines Prior to Maximal Exercise Test
Timeframe: Standing baseline blood draw, prior to maximal exercise test
Standing Concentration of Plasma Catecholamines at End of Maximal Exercise Test
Timeframe: This blood draw will occur at the very end or immediately following the maximal exercise test on the treadmill
Seated Baseline Heart Rate, Prior to Cold Pressor Test
Timeframe: Resting seated baseline, prior to cold pressor test, up to or around 5 minutes
Heart Rate Collected During Cold Pressor Test
Timeframe: Collected throughout the Cold Pressor Test, around 6 minutes in total
Standing Baseline Heart Rate, Prior to Fear Simulations
Timeframe: Standing baseline, prior to fear simulations, up to or around 5 minutes
Heart Rate, First Fear Simulation
Timeframe: Continuous heart rate will be collected during the first fear simulation, which will last around or up to 10 minutes
Heart Rate, First Calming Simulation
Timeframe: Continuous heart rate will be recorded during the first calming simulation, which will follow the first fear simulation and will last up to or around 10 minutes.
Heart Rate, Second Fear Simulation
Timeframe: Continuous heart rate will be recorded during the second fear simulation, which will follow the first calming simulation and will last up to or around 10 minutes.
Heart Rate, Second Calming Simulation
Timeframe: Continuous heart rate will be recorded during the second calming simulation, which will follow the second fear simulation and will last up to or around 10 minutes.
Heart Rate, Baseline Prior to Pain Patch
Timeframe: Baseline seated heart rate recordings will occur prior to application of pain patch, up to or around 5 minutes
Heart Rate, During Pain Patch
Timeframe: Continuous heart rate will be recorded following the application of the capsaicin pain patch, up to or around 15 minutes
Heart Rate, Baseline 12-Hour Fast
Timeframe: Resting baseline will be recorded prior (and on a separate day from) the 12-hour fast, up to or around 5 minutes.
Heart Rate, 12-Hour Fast
Timeframe: Seated heart rate recordings will occur following a 12-hour fast, up to or around 15 minutes.
Heart Rate, Seated Baseline, Caffeine Consumption
Timeframe: Resting baseline heart rate will be recording prior to caffeine consumption, up to or around 5 minutes
Heart Rate, Following Caffeine Consumption
Timeframe: Continuous heart rate recordings will occur immediately following caffeine consumption, up to or around 60 minutes.
Heart Rate, Baseline Prior to Maximal Exercise Test
Timeframe: Baseline heart rate recordings will occur prior to the maximal exercise test, up to or around 5 minutes.
Heart Rate, Maximal Exercise Test
Timeframe: Continuous heart rate recordings will take place throughout the maximal aerobic exercise test on the treadmill, up to or around 20 minutes
Seated Baseline Blood Pressure, Prior to Cold Pressor Test
Timeframe: Resting seated baseline, prior to cold pressor test, up to or around 5 minutes
Blood Pressure Collected During Cold Pressor Test
Timeframe: Collected throughout the Cold Pressor Test, around 6 minutes in total
Standing Baseline Blood Pressure, Prior to Fear Simulations
Timeframe: Standing baseline, prior to fear simulations, up to or around 5 minutes
Blood Pressure, First Fear Simulation
Timeframe: Continuous blood pressure will be recorded during the first fear simulation, which will last up to or around 10 minutes.
Blood Pressure, First Calming Simulation
Timeframe: Continuous blood pressure will be recorded during the first calming simulation, which will follow the first fear simulation and will last up to or around 10 minutes.
Blood Pressure, Second Fear Simulation
Timeframe: Continuous blood pressure will be recorded during the second fear simulation, which will follow the first calming simulation and will last up to or around 10 minutes.
Blood Pressure, Second Calming Simulation
Timeframe: Continuous blood pressure will be recorded during the second calming simulation, which will follow the second fear simulation and will last up to or around 10 minutes.
Blood Pressure, Baseline Prior to Pain Patch
Timeframe: Baseline seated blood pressure recordings will occur prior to application of pain patch, up to or around 5 minutes
Blood Pressure, During Pain Patch
Timeframe: Continuous blood pressure will be recorded following the application of the capsaicin pain patch, up to or around 15 minutes
Blood Pressure, Baseline 12-Hour Fast
Timeframe: Resting baseline will be recorded prior (and on a separate day from) the 12-hour fast, up to or around 5 minutes.
Blood Pressure, 12-Hour Fast
Timeframe: Seated blood pressure recordings will occur following a 12-hour fast, up to or around 15 minutes.
Blood Pressure, Seated Baseline, Caffeine Consumption
Timeframe: Resting baseline blood pressure will be recording prior to caffeine consumption, up to or around 5 minutes
Blood Pressure, Following Caffeine Consumption
Timeframe: Continuous blood pressure recordings will occur immediately following caffeine consumption, up to or around 60 minutes.
Blood Pressure, Baseline Prior to Maximal Exercise Test
Timeframe: Baseline blood pressure recordings will occur prior to the maximal exercise test, up to or around 5 minutes.
Blood Pressure, Maximal Exercise Test
Timeframe: Continuous blood pressure recordings will take place throughout the maximal aerobic exercise test on the treadmill, up to or around 20 minutes