Establishing Causality in the Relationship between Sleep and Migraine in a Global Sample: A Bayesian Approach

Background: There is a bidirectional link between sleep and migraine, however causality is difficult to determine. Previous studies rely on retrospective questionnaires, and small samples to support their findings. This study aimed to overcome this by teasing apart this relationship using sleep assessment and concomitant migraine data collected from a smartphone application using Bayesian modelling. Methods: Anonymized self-reported data on sleep and migraine from 11,166 global users (aged 18-81 years, mean: 41.21, standard deviation: 11.49) were collected from the Migraine Buddy application (Healint Pte. Ltd.) between 30th June and 31st December 2021. Measures included: demographics, start and end times of each sleep episode and migraine attack, and the pain intensity for each migraine attack (visual analogue scale 0-10). Bayesian regression models were used to predict occurrence of a migraine attack the next day based on users deviations from mean monthly sleep, number of sleep interruptions, and hours slept the night before in those reporting >4 and <25 migraine attacks on average per month. Conversely, we modelled whether attack occurrence and pain intensity could predict hours slept that same night. Results: Once exclusion criteria were applied, there were 724 users (129 males, 412 females, 183 unknown) with an average age of 41.88 years (SD = 11.63), with a mean monthly number of attacks of 9.94. A greater number of sleep interruptions (95% Highest Density Interval (95% HDI [0.112 - 0.205]) and deviation from a users mean sleep the night before (95% HDI [0.040 - 0.080]) were significant predictors of a next day migraine attack. Total hours slept was not a significant predictor (95% HDI [-0.04 - 0.04]). Pain intensity, but not attack occurrence was a positive predictor of hours slept. Discussion: Sleep fragmentation and deviation from typical sleep are the main drivers of the relationship between sleep and migraine, whereas overall sleep duration is not. Conversely, simply having a migraine attack does not predict sleep duration, it is the pain associated with an attack which alters sleep. This study has shed light on the causal mechanisms of sleep and migraine and highlights sleep hygiene as crucial in migraine management.