The 24-hour postdrome comes from diaries that stopped asking.

Why do I feel weird days after a migraine?

Thursday morning. The headache broke Monday night, the triptan did its job, and by any chart you're three days clear. Except you've reread the same email twice, the office lights still sit a notch too bright, and turning to check a blind spot pulls at something in your neck.

The patient-facing guidance describes this phase as short, something that wraps up soon after the pain does. So by Thursday you're either an outlier or something's wrong.

Neither, most likely. That guidance was never built to describe a Thursday.

The closed-diary problem

Migraine research learned to watch the headache closely and then look away. Diaries, trial instruments and symptom scales were built around pain: when it starts, how bad it gets, whether it's gone at two hours, whether it stays gone. Once the pain resolves, the instrument has done its job and the record closes.

Call it the closed-diary problem.

A study that stops asking about symptoms at a fixed point can't detect a postdrome that outlasts that point. The longest after-phase it can report is the length of its own observation window. So a 24-hour figure produced that way mostly tells you how long someone kept asking.

And every migraine tracker that ends the episode when the pain score hits zero carries the same blind spot into your own records.

Why 'up to 24 hours' sounds more settled than it is

The usual way to settle this goes: forums are anecdote, published figures are science, case closed. And there's something real in that position. Recall is messy. People blur the tail of one attack into the prodrome of the next, and poor sleep, medication effects and interictal symptoms can all feel like a hangover that won't lift.

But the clinical figure carries a bias of its own, and it only points one way. Short observation windows can't produce long durations. Patient recall can err in either direction; a closed diary can only err short.

The authorities don't agree with each other, either. The ICHD-3 glossary describes postdromal symptoms as ICHD-3 defines postdrome as a symptomatic phase, lasting up to 48 hours, following the resolution of pain in migraine attacks with or without aura. ([source](https://ichd-3.org/definition-of-terms/)), which doesn't match the patient-education number. When the figure shifts depending on which reference you open, you're looking at a convention.

What the published record actually measures

Start with acute-treatment trials. The FDA's 2018 guidance for these trials sets two co-primary endpoints, both at two hours: freedom from pain, and freedom from the patient's most bothersome symptom (photophobia, phonophobia or nausea). Trials commonly add sustained pain freedom out to 24 and 48 hours. Every timepoint is anchored to pain. Day-three concentration isn't on the form.

Diagnosis follows the same logic. ICHD-3 defines a migraine attack by its headache, lasting 4 to 72 hours untreated or unsuccessfully treated, and the postdrome sits in the comments and glossary rather than the diagnostic criteria.

The best direct evidence comes from a prospective electronic-diary study by Giffin and colleagues, published in Neurology in 2016 and designed specifically to capture the after-phase. 81% of participants reported at least one non-headache postdrome symptom, with tiredness the most common. On duration, patients' diaries tracked the postdrome after spontaneous pain resolution, and in 93% of attacks, return to normal occurred within 24 hours of pain resolving. ([source](https://pubmed.ncbi.nlm.nih.gov/27335112/)). That window is the number to check before trusting any duration figure.

Patients describe something longer. In r/migraine, one commenter said their migraine symptoms include brain fog that can last for up to a week: "mine also usually includes brain fog that can last for up to a week." ([source](https://www.reddit.com/r/migraine/comments/z3tfa7/feeling_like_im_in_a_brain_fog_for_days_after_a/))

One attack, walked through a closed diary

Run one attack through a typical tracker. Pain starts Monday afternoon, gets logged as severe, a triptan goes in, and by late evening the pain score reads zero. The app saves the episode. Done.

Tuesday brings the bone-deep tiredness. Wednesday, words go missing mid-sentence. Thursday, the grocery store lighting is still too much. None of it has a field, so none of it gets saved.

Three months later the neurologist reviews an export showing attacks that last most of an afternoon. The patient says they lose half the week, and it lands like exaggeration because the printout disagrees. Repeat that appointment across a whole clinic's patient list and you get a literature that calls the after-phase a day.

If the 24-hour figure measures a window, three things change

For patients, a foggy Thursday stops being evidence that you're recovering wrong. It's a phase the instruments didn't follow.

For clinicians, attack counts undercount the cost. Someone with four attacks a month and three-day tails loses far more functional time than an attack log shows, and that gap matters for workplace accommodations and disability paperwork that ask how many days were affected.

For research, the fix is cheap in principle: keep the diary open until the patient closes it. A study can't report a postdrome longer than the time it spent asking. Until one asks long enough, treat 'up to 24 hours' as a floor set by the observation window, and stop quoting it as a ceiling.

Keeping the record open past the pain

We built Postdrome around the part of the attack the diary used to drop. Its timeline keeps tracking after the pain ends, so fatigue, brain fog, residual light sensitivity and neck stiffness log as continuous symptoms across the days that follow. Aura Mode keeps logging possible when the screen itself is the problem.

What we won't claim: that Postdrome has already settled this. Your records stay on your device, so we aren't sitting on a pooled dataset, and we're not going to wave one around. What a kept-open timeline can settle is your own question. How long does your postdrome run? Does it stretch after certain attacks or treatments? How many days does it take from a month?

Export it, bring it to your neurologist, and the after-phase finally has a record of its own.

What we're tracking next

Two things. First, any prospective study that reports postdrome duration alongside a post-headache diary window longer than 72 hours, because that's the design that could actually move the number. Second, whether a future ICHD revision gives the postdrome formal criteria instead of a glossary line. If either lands, the 24-hour figure finally gets tested.