Trial Review

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Trial registered on ANZCTR


Registration number
ACTRN12625000938404p
Ethics application status
Submitted, not yet approved
Date submitted
15/08/2025
Date registered
29/08/2025
Date last updated
29/08/2025
Date data sharing statement initially provided
29/08/2025
Type of registration
Prospectively registered

Titles & IDs
Public title
How do different amounts of caffeine affect sleep in healthy adult females
Scientific title
Dose effects of caffeine on subsequent sleep in healthy female adults with differing hormonal profiles: A randomised clinical crossover trial
Secondary ID [1] 315139 0
None
Universal Trial Number (UTN)
Trial acronym
Linked study record

Health condition
Health condition(s) or problem(s) studied:
Sleep 338567 0
Condition category
Condition code
Neurological 334870 334870 0 0
Studies of the normal brain and nervous system
Mental Health 334949 334949 0 0
Studies of normal psychology, cognitive function and behaviour
Metabolic and Endocrine 334950 334950 0 0
Normal metabolism and endocrine development and function

Intervention/exposure
Study type
Interventional
Description of intervention(s) / exposure
The study will be a placebo-controlled, double-blind, randomised crossover design. Participants will be complete three conditions a single time each separated by a 48-hour washout. Conditions are:
• A capsule containing placebo (filled with microcrystalline cellulose to weight-match) consumed eight hours prior to bedtime
• A capsule containing caffeine 100 mg (filled with microcrystalline cellulose to weight-match) consumed eight hours prior to bedtime
• A capsule containing caffeine 400 mg consumed eight hours prior to bedtime

Data collection will occur in the home environment of each participant. Participants will be required to send a text message confirmation to confirm compliance with the capsule consumption.

On each condition day, participants will provide a saliva sample seven hours prior to bedtime, five minutes prior to bedtime, and five minutes upon waking the next morning. Immediately prior to bedtime, participants will wear an Oura ring and Activity Monitor and attach the Somfit device (Compumedics, Australia) to their forehead to measure the subsequent sleep bout and. Subjective measures of sleep will be recorded through the daily sleep diary and the Karolinska Sleepiness Scale (KSS).

There will be five groups in the study:
• Naturally cycling group
o Female aged between 18 and 40 years (inclusive)
o Reports a natural menstrual cycle of 21 to 35 days based off the calendar counting method for at least three months prior to study enrollment
• Oral contraception group
o Female aged between 18 and 40 years (inclusive)
o Reports regular use of a monophasic contraceptive pill for at least three months prior to study enrollment
• Hormonal intra-uterine device (IUD) group
o Female aged between 18 and 40 years (inclusive)
o Reports using a hormonal IUD for at least three months prior to study enrollment
• Post menopausal group
o Female aged 40 years or older
o Reports cessation of menstruation for at least 12 months prior to study enrollment with no use of hormone replacement therapy in the three months prior to study enrollment
• Post menopausal group with hormonal replacement therapy
o Female aged 40 years or older
o Reports cessation of menstruation for at least 12 months prior to study enrollment and reports regular use of hormone replacement therapy, continuous combined or estrogen-only regimen, for at least three months prior to study enrollment
Intervention code [1] 331765 0
Lifestyle
Comparator / control treatment
The placebo will contain microcrystalline cellulose administered in an identical appearing and weight matched capsule.
Control group
Placebo

Outcomes
Primary outcome [1] 342498 0
Objective sleep outcome: Total sleep time (min)
Timepoint [1] 342498 0
Subsequent overnight sleep bout (eight hours from capsule consumption)
Primary outcome [2] 342499 0
Objective sleep outcome: Sleep efficiency (%) (calculated as total sleep time/time in bed x 100)
Timepoint [2] 342499 0
Subsequent overnight sleep bout (eight hours from capsule consumption)
Primary outcome [3] 342500 0
Objective sleep outcome: Sleep onset latency (min)
Timepoint [3] 342500 0
Subsequent overnight sleep bout (eight hours from capsule consumption)
Secondary outcome [1] 451061 0
Objective sleep outcome: Wake after sleep onset (min)
Timepoint [1] 451061 0
Subsequent overnight sleep bout (eight hours from capsule consumption)
Secondary outcome [2] 451062 0
Objective sleep outcome: Absolute sleep architecture (min)
Timepoint [2] 451062 0
Subsequent overnight sleep bout (eight hours from capsule consumption)
Secondary outcome [3] 451063 0
Objective sleep outcome: Sleep architecture relative to total sleep time (%)
Timepoint [3] 451063 0
Subsequent overnight sleep bout (eight hours from capsule consumption)
Secondary outcome [4] 451064 0
Subjective sleep outcome: Total sleep time (min)
Timepoint [4] 451064 0
Within 30 minutes of waking the next morning
Secondary outcome [5] 451065 0
Subjective sleep outcome: Sleep efficiency (%) (calculated as total sleep time/time in bed x 100)
Timepoint [5] 451065 0
Within 30 minutes of waking the next morning
Secondary outcome [6] 451066 0
Subjective sleep outcome: Sleep onset latency (min)
Timepoint [6] 451066 0
Within 30 minutes of waking the next morning
Secondary outcome [7] 451067 0
Subjective sleep outcome: Wake after sleep onset (min)
Timepoint [7] 451067 0
Within 30 minutes of waking the next morning
Secondary outcome [8] 451068 0
Subjective sleep outcome: Sleep quality (1-5 Likert scale)
Timepoint [8] 451068 0
Within 30 minutes of waking the next morning
Secondary outcome [9] 451069 0
Acute sleepiness
Timepoint [9] 451069 0
Immediately prior to bedtime
Secondary outcome [10] 451070 0
Salivary caffeine concentration (µg.mL-1)
Timepoint [10] 451070 0
Seven hours prior to bedtime, five minutes prior to bedtime, and five minutes upon waking the next morning
Secondary outcome [11] 451071 0
Genotyping of single nucleotide polymorphisms related to sleep and caffeine metabolism
Timepoint [11] 451071 0
Once across data collection

Eligibility
Key inclusion criteria
• Must be able to provide written informed consent upon having the study procedure explained to them verbally and/or in writing
• Healthy (assessed via initial screening questionnaire and the 12-item General Health Questionnaire,
• Free from any known sleep disorders (assessed via the Pittsburgh Sleep Quality Index and Morningness-Eveningness Questionnaire).
• Regular caffeine consumer with habitual consumption between 2-5 mg·kg·-1day-1 (assessed via validated caffeine questionnaire)
• Willing to consume a standardised dose of caffeine on each day of the intervention period and refrain from additional caffeine intake
• Willing to refrain from consuming alcohol during the intervention period
• Willing to refrain from napping during the intervention period
• Non-smoker (no nicotine consumption via vaping, cigarettes, or chewing tobacco)
• Naturally cycling group
o Female aged between 18 and 40 years (inclusive)
o Reports a natural menstrual cycle of 21 to 35 days based off the calendar counting method for at least three months prior to study enrollment
• Oral contraception group
o Female aged between 18 and 40 years (inclusive)
o Reports regular use of a monophasic contraceptive pill for at least three months prior to study enrollment
• Hormonal intra-uterine device (IUD) group
o Female aged between 18 and 40 years (inclusive)
o Reports using a hormonal IUD for at least three months prior to study enrollment
• Post menopausal group
o Female aged 40 years or older
o Reports cessation of menstruation for at least 12 months prior to study enrollment with no use of hormone replacement therapy in the three months prior to study enrollment
• Post menopausal group with hormonal replacement therapy
o Female aged 40 years or older
o Reports cessation of menstruation for at least 12 months prior to study enrollment and reports regular use of hormone replacement therapy, continuous combined or estrogen-only regimen, for at least three months prior to study enrollment
Minimum age
18 Years
Maximum age
No limit
Sex
Females
Can healthy volunteers participate?
Yes
Key exclusion criteria
• Participant has a clinically diagnosed sleep disorder
• Participant has a diagnosed menstrual cycle dysfunction or disorder
• Participant is pregnant
• Participant has a known medical condition or current illness that may affect sleep
• Participant has consumed cigarettes, illicit drugs, or medications known to affect sleep in the month prior to study enrollment
• Participant has undertaken overnight shift work in the month prior to study enrollment
• Participant has undertaken international time zone travel in the month prior to study enrollment

Study design
Purpose of the study
Prevention
Allocation to intervention
Randomised controlled trial
Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)
Allocation is not concealed due to inclusion criteria requirements dictating group
Methods used to generate the sequence in which subjects will be randomised (sequence generation)
Latin square block design generated using a random number sequence generator (i.e., 1 to 4)
Masking / blinding
Blinded (masking used)
Who is / are masked / blinded?
The people receiving the treatment/s
The people administering the treatment/s
The people assessing the outcomes
The people analysing the results/data
Intervention assignment
Crossover
Other design features
Phase
Not Applicable
Type of endpoint/s
Statistical methods / analysis

Recruitment
Recruitment status
Not yet recruiting
Date of first participant enrolment
Anticipated
29/09/2025
Actual
Date of last participant enrolment
Anticipated
Actual
Date of last data collection
Anticipated
Actual
Sample size
Target
60
Accrual to date
Final
Recruitment in Australia
Recruitment state(s)
QLD

Funding & Sponsors
Funding source category [1] 319716 0
University
Name [1] 319716 0
Australian Catholic University
Country [1] 319716 0
Australia
Primary sponsor type
University
Name
Australian Catholic University
Address
Country
Australia
Secondary sponsor category [1] 322224 0
None
Name [1] 322224 0
Address [1] 322224 0
Country [1] 322224 0

Ethics approval
Ethics application status
Submitted, not yet approved
Ethics committee name [1] 318269 0
ACU Human Research Ethics Committee
Ethics committee address [1] 318269 0
Ethics committee country [1] 318269 0
Australia
Date submitted for ethics approval [1] 318269 0
14/08/2025
Approval date [1] 318269 0
Ethics approval number [1] 318269 0

Summary
Brief summary
Trial website
Trial related presentations / publications
Public notes

Contacts
Principal investigator
Name 143650 0
Dr Carissa Gardiner
Address 143650 0
Australian Catholic University, 1100 Nudgee Road, Banyo QLD 4014
Country 143650 0
Australia
Phone 143650 0
+61 439833967
Fax 143650 0
Email 143650 0
[email protected]
Contact person for public queries
Name 143651 0
Carissa Gardiner
Address 143651 0
Australian Catholic University, 1100 Nudgee Road, Banyo QLD 4014
Country 143651 0
Australia
Phone 143651 0
+61 439833967
Fax 143651 0
Email 143651 0
[email protected]
Contact person for scientific queries
Name 143652 0
Carissa Gardiner
Address 143652 0
Australian Catholic University, 1100 Nudgee Road, Banyo QLD 4014
Country 143652 0
Australia
Phone 143652 0
+61 439833967
Fax 143652 0
Email 143652 0
[email protected]

Data sharing statement
Will the study consider sharing individual participant data?
No


What supporting documents are/will be available?

No Supporting Document Provided


Results publications and other study-related documents

Documents added manually
No documents have been uploaded by study researchers.

Documents added automatically
No additional documents have been identified.