Effects of Caffeine on Cerebral Blood Flow

Effects of Caffeine on Cerebral Blood Flow in Clinically Healthy Young People

The goal of this clinical trial is to evaluate in clinically healthy young people if:

• after caffeine ingestion, there are variations in blood velocity of the middle cerebral arteries (VMCA),
• this variation is dependent on the administered dose.

Transcranial Doppler ultrasonography was used to record blood VMCA in three groups of 15 clinically healthy young adults each - no caffeine, low caffeine (45 mg) and high caffeine group (120 mg). Transcranial Doppler ultrasonography provided simultaneous bilateral VMCA measurements while subjects performed functional tests (hyperventilation and hypoventilation orders) and three cognitive activities (Test 1, short-term remembering, Test 2, solving a vocabulary problem, and Test 3, solving a math problem) each in 31-second tests with 1-minute rest between them. Participants were assessed before and 30 minutes after caffeine ingestion.

Study Overview

• Status: Completed
• Conditions: Cardiovascular System
• Intervention / Treatment: Other: Placebo; Other: Anhydrous caffeine (45mg); Other: Anhydrous caffeine (120mg)

Detailed Description

Were used in the study, Capsules dosed with 45mg and 120 mg of anhydrous caffeine and flour capsules as a placebo. In the preparation of the capsules, a semi-automatic capsulator No. 0 (Capsunorm® by Tecnyfarma®) were used, colorless hard gelatin capsules No. 0 by Acopharma® and anhydrous caffeine (Biochem®, C.A.S. 58-08-2).

Viasys Sonara transcranial Doppler unit and a 2 MHz probe were used to sample the middle cerebral artery at depths of 60 millimeters, using emission doppler pulsed performing spectral analysis in real time. Two probes (bilaterally) of 2MHz were placed at a depth between 55 and 60 mm, thus making it possible to analyse both middle cerebral arteries simultaneously.

Each participant was asked not to ingest caffeine and exercise vigorously for at least 12 hours before the assessment. In the case of smokers, they were also asked not to smoke for at least 2 hours before the evaluation. The laboratory had medium luminosity, silent and controlled temperature (23º/24ºC). To avoid inter-observer errors, all examinations were performed by the same investigator who was not aware of what dose was/had been administered to the participant.

Subjects were tested while seated in a reclining chair located in a dimly lit, sound-attenuated room and performed the activities with their eyes closed.

• Study Type: Interventional
• Enrollment (Actual): 45
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Portugal
  • Coimbra, Portugal, 3046-854
    • Coimbra Health School

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

• clinically healthy young people

Exclusion Criteria:

• Individuals with hypertension, high cholesterol, diabetes, arrhythmias, carotid sinus syndrome, severe carotid stenosis and who were in an unstable clinical situation.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: No caffeine; The control group took flour capsules.	Other: Placebo; Flour capsules as a placebo.
Experimental: Low caffeine; Group with relatively small amount of caffeine (45 mg) administered.	Other: Anhydrous caffeine (45mg); Capsules dosed with 45mg of anhydrous caffeine.
Experimental: High caffeine; Group with greater amount of caffeine (120 mg) administered.	Other: Anhydrous caffeine (120mg); Capsules dosed with 120mg of anhydrous caffeine.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in Mean Velocity (Basal)	Changes in Mean Velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Mean Velocity (Hypoventilation)	By performing Hypoventilation, changes in Mean Velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Mean Velocity (Hyperventilation)	By performing Hyperventilation, changes in Mean Velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Mean Velocity (Short-term memory test)	With short-term memory test, changes in Mean Velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Mean Velocity (Vocabulary problem)	With solving vocabulary problems, changes in Mean Velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Mean Velocity (Math problem.)	With solving math problems, changes in Mean Velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Peak systolic velocity (Basal)	Changes in Mean Velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Peak systolic velocity (Hypoventilation)	By performing Hypoventilation, changes in Peak systolic velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Peak systolic velocity (Hyperventilation)	By performing Hyperventilation, changes in Peak systolic velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Peak systolic velocity (Short-term memory test)	With short-term memory test, changes in Peak systolic velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Peak systolic velocity (Vocabulary problems)	With solving vocabulary problems, changes in Peak systolic velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Peak systolic velocity (Math problems)	With solving math problems, changes in Peak systolic velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Vend-diastolic velocity (Basal)	Changes in Mean Velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Vend-diastolic velocity (Hypoventilation)	By performing Hypoventilation, changes in Vend-diastolic velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Vend-diastolic velocity (Hyperventilation)	By performing Hyperventilation, changes in Vend-diastolic velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Vend-diastolic velocity (Short-term memory test)	With short-term memory test, changes in Vend-diastolic velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Vend-diastolic velocity (Vocabulary problems)	With solving vocabulary problems, changes in Vend-diastolic velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Vend-diastolic velocity (Math problems)	With solving math problems, changes in Vend-diastolic velocity, measure in m/s from baseline to 30 minutes after caffeine ingestion.	30 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Changes in Heart Rate (Basal)	Changes in Heart Rate, measure in bpm from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Heart Rate (Hypoventilation)	By performing Hypoventilation, changes in Heart Rate, measure in bpm from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Heart Rate (Hyperventilation)	By performing Hyperventilation, changes in Heart Rate, measure in bpm from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Heart Rate (Short-term memory test)	With short-term memory test, changes in Heart Rate, measure in bpm from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Heart Rate (Vocabulary problems)	With solving vocabulary problems, changes in Heart Rate, measure in bpm from baseline to 30 minutes after caffeine ingestion.	30 minutes
Changes in Heart Rate (Math problems)	With solving math problems, changes in Heart Rate, measure in bpm from baseline to 30 minutes after caffeine ingestion.	30 minutes

Collaborators and Investigators

• Sponsor: Escola Superior de Tecnologia da Saúde de Coimbra
• Investigators: Principal Investigator: Hélder Santos, PhD, Polytechnic Institute of Coimbra - Coimbra Health School

Study record dates

Study Major Dates

• Study Start (Actual): May 1, 2021
• Primary Completion (Actual): June 1, 2021
• Study Completion (Actual): June 1, 2021

Study Registration Dates

• First Submitted: April 6, 2023
• First Submitted That Met QC Criteria: May 10, 2023
• First Posted (Actual): May 19, 2023

Study Record Updates

• Last Update Posted (Actual): May 19, 2023
• Last Update Submitted That Met QC Criteria: May 10, 2023
• Last Verified: May 1, 2023

More Information

Terms related to this study

• Keywords: caffeine; Transcranial Doppler ultrasonography; Middle Cerebral Artery; functional tests; cognitive activities
• Additional Relevant MeSH Terms: Physiological Effects of Drugs; Neurotransmitter Agents; Molecular Mechanisms of Pharmacological Action; Enzyme Inhibitors; Purinergic Antagonists; Purinergic Agents; Phosphodiesterase Inhibitors; Purinergic P1 Receptor Antagonists; Central Nervous System Stimulants; Caffeine
• Other Study ID Numbers: CCBF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No