Sleep & circadian disruption
Insomnia, unrefreshing sleep, or circadian misalignment — both a cause and amplifier of fatigue and brain fog.
Illness and prolonged time in bed readily upset sleep and circadian rhythm, producing insomnia or hypersomnia that then drives fatigue, brain fog, and low mood. The single highest-yield action here is screening for obstructive sleep apnea (STOP-BANG → a home sleep test), which is common, undiagnosed, treatable, and both mimics and worsens Long COVID. CBT-I has the best evidence for chronic insomnia generally; melatonin, light therapy, and orexin antagonists are low-risk but unproven specifically for Long COVID (RECOVER-SLEEP results are pending). Wakefulness drugs like modafinil can mask exertional limits and should be reserved for true excessive sleepiness.
How it's tested
Sleep-apnea screen (STOP-BANG → home sleep test)
A free questionnaire that, if positive, leads to an inexpensive home sleep apnea test. Sleep apnea is common, undiagnosed, treatable, and both mimics and worsens Long COVID.
In-lab sleep study (polysomnography)
Comprehensive overnight study for sleep apnea and other sleep disorders when a home test is inconclusive.
Sleep diary / wearable tracking
Two weeks of self-tracked sleep timing and quality. Useful for circadian patterns and to triage, but wearables are unreliable for staging.
Treatment options & their evidence
Graded honestly — including treatments that failed in good trials, which is worth knowing.
CBT-I (CBT for insomnia)
Strong evidenceFirst-line, guideline-recommended for chronic insomnia generally, with durable effects; no completed Long COVID-specific RCT yet but the best-evidenced sleep option here.
Caution: The sleep-restriction component can transiently worsen daytime fatigue — pace carefully if PEM is present.
Treat the underlying condition
Strong evidenceWhen a separate condition (thyroid, iron deficiency, sleep apnea, B12, diabetes, depression) is found, treating it directly is well-established and can resolve the symptoms entirely.
Melatonin
Weak evidenceLow-risk chronobiotic/hypnotic; no completed Long COVID insomnia RCT (RECOVER-SLEEP pending). Low-dose timed use differs from high-dose hypnotic use.
Caution: Daytime grogginess; OTC dose/content varies widely.
Bright-light therapy
Weak evidencePlausible low-risk circadian intervention; the only Long COVID data is a small uncontrolled pre-post study. RECOVER-SLEEP is testing it controlled.
Caution: Mistimed exposure can worsen circadian misalignment; mania risk in bipolar.
Modafinil / wakefulness agents
Anecdotal onlyCautionInvestigational for Long COVID (RECOVER-SLEEP hypersomnia arm). For genuine excessive daytime sleepiness, not generic fatigue.
Caution: Can MASK exertional limits and precipitate post-exertional crashes in PEM patients. Headache, anxiety, reduces hormonal-contraceptive efficacy.