# Information-Theoretic Trigger Surprisal and Future Headache Activity

## TL;DR

This study found that unpredictable daily experiences, measured as 'surprisal', are linked to increased migraine risk in the short term.

## Contribution

The study introduces surprisal as a novel, individualized metric for predicting migraine attacks based on daily unpredictability.

## Key findings

- Higher surprisal scores were significantly associated with increased migraine risk within 12 and 24 hours.
- The association between surprisal and migraine onset showed nonlinear properties and was moderated by recent surprisal history.
- Incorporating surprisal into digital tools could improve personalized migraine prevention strategies.

## Abstract

This cohort study assesses the association between information-theoretic trigger surprisal and future headache activity in patients with migraine.

Is there an association between information-theoretic trigger surprisal and future headache activity?

In this cohort study including 109 participants, total surprisal score was associated with future migraine risk at 12 hours and 24 hours.

The findings of this study underscore the value of a person-centered, information-theoretic approach to understanding migraine triggers, one that moves beyond static lists of potential causes to account for the unpredictable and context-sensitive nature of daily life.

Identifying migraine triggers is a common goal for individuals with migraine but remains challenging due to the vast number of possible triggers and their fluctuating nature. A measurement system quantified through information-theoretic surprisal (ie, the negative logarithm of the probability of an observed exposure) could be valuable for evaluating the wide range of possible triggers for future migraine attacks.

To evaluate the association between surprisal and future headache attacks.

This cohort study conducted from April 2021 to December 2024 included 109 participants with migraine who completed diary entries of potential migraine triggers and migraine attacks within 12 and 24 hours after trigger exposure twice daily for up to 28 days.

Diary items captured exposure to potential behavioral, emotional, and environmental migraine triggers. To quantify the unexpectedness of a participant’s daily experiences, total surprisal scores measured in bits of information was calculated using within-person empirical probability distributions to reflect how atypical each day’s experiences were.

The primary outcomes were occurrence of a headache attack within 12 and 24 hours (0, no attack; 1, attack) after trigger exposure. A headache attack was defined as any self-reported headache with pain greater than 0 on a 0 to 10 numeric rating scale where 0 was no pain and 10 was the worst pain, and any pattern of secondary symptoms (eg, photophobia and phonophobia). Intraclass correlation coefficients and variance components were calculated to quantify between-person differences in baseline risk and the strength of the surprisal association.

A total of 109 participants were included in the analysis. Participants’ median age was 35 (26.0-46.0) years, and the majority were female (102 [93.5%]). One hundred and four participants had complete diaries (5176 diary entries) and experienced headaches on 1518 of 5145 days (29.5%). Higher surprisal was significantly associated with increased migraine risk within 12 hours (odds ratio [OR], 1.86; 95% CI, 1.12-3.08; P = .02) and 24 hours (OR, 2.15; 95% CI, 1.44-3.20; P < .001), with a higher OR indicating a stronger association observed at the longer interval. The association between current surprisal and migraine onset was moderated by recent surprisal history and exhibited nonlinear properties at 12 hours. Random-effects models revealed substantial between-person variability and, after adjustment, the association between total surprisal and headache attack risk was attenuated (OR, 1.56; 95% CI, 1.01-2.40; P = .04 for 12 hours and OR, 1.88; 95% CI, 1.27-2.79; P = .002 for 24 hours).

In this cohort study, surprisal offered a novel, individualized measure of trigger unpredictability that was associated with short-term migraine risk. Incorporating surprisal into digital tools may improve personalized prevention strategies, moving beyond static trigger lists to a dynamic, context-aware model of migraine self-management.