Caffeine Abstinence Before MSLT
Patients must discontinue caffeine-containing substances for at least 2 weeks (14 days) before undergoing a Multiple Sleep Latency Test (MSLT).
Rationale for Caffeine Withdrawal
The MSLT measures physiological sleepiness and requires elimination of all substances that could mask true sleep tendency. Caffeine is a CNS stimulant that directly interferes with MSLT interpretation by artificially prolonging sleep latency and suppressing REM sleep onset 1, 2. The American Geriatrics Society explicitly recommends discontinuing stimulants—including caffeine—before MSLT testing 3, 2.
Specific Withdrawal Timeline
- A minimum 2-week caffeine-free period is necessary to allow complete washout and resolution of tolerance effects 1, 2
- This duration aligns with the recommended 7-14 day pre-test actigraphy monitoring period, during which caffeine should already be eliminated 1, 2
- Caffeine has a half-life of 3-7 hours in healthy adults, but chronic use produces physiological adaptations that require longer washout periods 4, 5
What Counts as Caffeine
Patients must avoid all sources of caffeine, not just obvious ones:
- Coffee, tea, and soft drinks (the most common dietary sources) 6, 7
- Energy drinks and dietary supplements (which may contain unlabeled caffeine from guarana or other herbal sources) 8
- Chocolate and cocoa-containing products 7
- Over-the-counter medications including some analgesics, cold remedies, and weight-loss supplements 4, 8
Critical Medication Interactions
Certain prescription medications inhibit caffeine metabolism via CYP1A2 enzyme, causing nonlinear accumulation even from modest intake 4. Patients taking fluvoxamine, mexiletine, clozapine, enoxacin, or other CYP1A2 inhibitors may have prolonged caffeine effects lasting well beyond typical elimination times 4. For these patients, verify complete abstinence and consider extending the caffeine-free period beyond 2 weeks.
Comprehensive Pre-Test Preparation
The caffeine withdrawal period should coincide with other mandatory MSLT preparations:
- Discontinue all stimulants (amphetamines, methylphenidate, modafinil) and sedating medications (benzodiazepines, hypnotics, antihistamines) during the same 2-week period 3, 2
- Wear wrist actigraphy for 7-14 days to objectively document adequate sleep (≥6 hours nightly for adults) 1, 9
- Maintain a regular sleep-wake schedule throughout the pre-test period 1
- Complete overnight polysomnography immediately before the MSLT to rule out sleep apnea and other disorders 3, 9
Common Pitfalls
- Patients frequently underestimate their caffeine intake because they don't recognize non-beverage sources 6, 8
- Caffeine withdrawal itself can cause headache, fatigue, and anxiety for several days, which patients may misinterpret as worsening of their sleep disorder 5
- Smokers and psychiatric patients typically consume more caffeine than they report 6, requiring specific questioning about all sources
- Inadequate caffeine withdrawal is a leading cause of false-negative MSLT results (normal sleep latency despite true narcolepsy) 1, 2
Documentation Requirements
- Instruct patients to maintain a detailed log of all caffeine-containing products consumed (or avoided) during the 2-week pre-test period 1
- Review this log alongside actigraphy data to verify compliance before proceeding with the MSLT 1, 2
- Any caffeine consumption during the withdrawal period invalidates the test and requires rescheduling 2