Clinical trial NCT00487227: Effects of Low Doses of Caffeine on Mood, Physiology and Mental Function
Official title: Levels of Caffeine Lower Than Those Found in Decaffeinated Beverages Exert Effects on Cognition, Mood, and Autonomic Activity
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Healthy
Keywords: caffeine
coffee
decaffeinated
cognition
mood
autonomic
Lead sponsor: Northumbria University
Sponsor class: OTHER
First posted: 2007-06-18
Enrollment: 20
Sex: ALL
Minimum age (years): 18
Maximum age (years): 35
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Primary purpose: BASIC_SCIENCE

Brief summary: It is often assumed that levels of caffeine found in 'decaffeinated' beverages are below any psychopharmacological threshold. However, recent findings indicate that caffeine doses as low as 9 mg may be psychoactive. The effects of caffeine have also been shown up to 6 hours post-administration. The study aimed to establish the lowest active dose of caffeine, and to ascertain the duration of any effects.

Detailed description: The majority of recent caffeine studies have evaluated doses in the range of 75 - 150 mg or 1 - 2 mg/kg (approximately 130 - 260 ml fresh coffee). Such doses produce well characterised effects; including increased 'alertness', and improvements to measures of reaction time and sustained attention. A previous study has demonstrated improvements to performance following 9 mg caffeine, which represents the lowest known psychoactive dose of caffeine. A number of these effects, including elevated salivary caffeine levels, were still apparent at 6 hours post-caffeine consumption (9). Findings showing effects of 12.5 and 9 mg caffeine are important as these are approaching the levels found in decaffeinated beverages, which are assumed to have no behavioural or physiological effects. However, despite extensive research in this area, the lower threshold for psychoactive effects has not been established. A randomised, placebo-controlled, double-blind, balanced crossover study was undertaken. 20 young men and women (13 female, mean age 20.7 years, standard deviation 2.4) undertook computerised assessments of memory and attention and rated subjective mood. Autonomic activity and salivary caffeine were co-monitored. Assessment took place at baseline, 1, 3, 6, and 9 hours post-administration of placebo, 2.5, 5, and 10 mg caffeine (on separate days) administered in 150 ml fruit juice.

Eligibility criteria: Inclusion Criteria:

* native English speaker

Exclusion Criteria:

* pregnancy
* medication
* anaemia
* heart disorder
* diabetes
* respiratory disorder
* epilepsy
* asthma
* panic attacks
* habitual smoking
* food allergy

Primary outcomes:
measure: Change from baseline speed of attention
timeFrame: 1 hour
measure: Change from baseline speed of attention
timeFrame: 3 hours
measure: Change from baseline speed of attention
timeFrame: 6 hours
measure: Change from baseline speed of attention
timeFrame: 9 hours
Secondary outcomes:
measure: Change from baseline accuracy of attention
timeFrame: 1 hour
measure: Change from baseline accuracy of attention
timeFrame: 3 hours
measure: Change from baseline accuracy of attention
timeFrame: 6 hours
measure: Change from baseline accuracy of attention
timeFrame: 9 hours
measure: Change from baseline speed of memory
timeFrame: 1 hour
measure: Change from baseline speed of memory
timeFrame: 3 hours
measure: Change from baseline accuracy of memory
timeFrame: 6 hours
measure: Change from baseline accuracy of memory
timeFrame: 9 hours
measure: Change from baseline subjective mood
timeFrame: 1 hour
measure: Change from baseline subjective mood
timeFrame: 3 hours
measure: Change from baseline subjective mood
timeFrame: 6 hours
measure: Change from baseline subjective mood
timeFrame: 9 hours
measure: Change from baseline blood pressure
timeFrame: 1 hour
measure: Change from baseline blood pressure
timeFrame: 3 hours
measure: Change from baseline blood pressure
timeFrame: 6 hours
measure: Change from baseline blood pressure
timeFrame: 9 hours
measure: Change from baseline heart rate
timeFrame: 1 hour
measure: Change from baseline heart rate
timeFrame: 3 hours
measure: Change from baseline heart rate
timeFrame: 6 hours
measure: Change from baseline heart rate
timeFrame: 9 hours
measure: Change from baseline salivary caffeine levels
timeFrame: 1 hour
measure: Change from baseline salivary caffeine levels
timeFrame: 3 hours
measure: Change from baseline salivary caffeine levels
timeFrame: 6 hours
measure: Change from baseline salivary caffeine levels
timeFrame: 9 hours
Other outcomes:
Locations:
Study officials:
affiliation: Northumbria University
name: Andrew Scholey
role: PRINCIPAL_INVESTIGATOR
References: