None listed
Conditions
Brief summary
The extent to which caffeine disrupts subsequent sleep depends largely on the amount and timing of intake relative to bedtime, with more pronounced reductions in sleep quantity and quality as caffeine is consumed closer to bedtime. However, a common limitation of the current evidence is its applicability to females with varying hormonal profiles. Oral contraceptive use can slow caffeine metabolism, with greater caffeine exposure potentially altering the effects of caffeine on subsequent sleep. Understanding the influence of hormonal profile will improve the applicability of caffeine-related sleep recommendations for females. This study has three key objectives: 1) Investigate the effects of caffeine dose on subsequent sleep in healthy adult females; 2) Investigate whether the time course of caffeine metabolism differs according to hormonal profile; and 3) Examine whether differences in caffeine metabolism alter the effects of caffeine on subsequent sleep.
Interventions
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 cons
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
Sponsors
Australian Catholic University
Study design
Allocation
Randomised controlled trial
Intervention model
Crossover
Primary purpose
Prevention
Masking
Blinded (masking used) (Subject, Caregiver, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
All
Age
18 Years to No maximum
Healthy volunteers
Yes
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
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
Outcome results
None listed