Chronotype and primary headaches: What a population‐based study reveals

Migraine and tension-type headache (TTH) are the most prevalent primary headache disorders, together accounting for a large share of the global disability burden associated with headaches. Beyond the classical clinical features, that is, unilateral, pulsating pain and associated symptoms in migraine versus bilateral, pressing discomfort in TTH,1 there is growing recognition that individual differences in circadian rhythm may influence not only susceptibility to headache disorders but also their clinical features.2 Chronotype describes an individual's intrinsic circadian preference for the timing of sleep, wakefulness, and daily activity, commonly characterized as morning (“early bird”), intermediate, or evening (“night owl”) types. These preferences reflect underlying circadian rhythm, which regulates hormonal release, autonomic function, pain sensitivity, and sleep–wake cycles.2-6 Variations in circadian preference may therefore interact with these systems to shape vulnerability to stress, sleep disruption, and mood disturbances, all known modulators of headache burden.7-9 Although the relationship between chronotype and migraine has been suggested, with evening chronotype more frequent among patients with migraine and associated with increased headache frequency and susceptibility to migraine-related disabilities,10 available data remain limited and inconclusive2 and are even more sparse for TTH. In the current issue of Headache, Jung et al. present the results of a population-based study designed to examine the distribution of chronotypes among individuals with migraine and TTH and evaluate the association between chronotype and clinical headache features.11 Using a cross-sectional design, the authors analyzed nationwide baseline data from the population-based Circannual Change in Headache and Sleep study conducted in the Republic of Korea in 2010. Chronotype was assessed using the Korean version of the Horne and Östberg Morningness–Eveningness Questionnaire (MEQ), a validated 19-item self-report instrument that captures individual circadian preference, with lower and higher scores indicating stronger eveningness and morningness, respectively. By integrating a large-scale epidemiological dataset and a standardized measure of chronotype, this study provides an important insight for understanding how circadian preference may relate to headache phenotypes at the population level. The study revealed that both those with migraine and those with TTH had a higher prevalence of evening chronotypes and a lower prevalence of morning chronotypes in comparison with individuals without headache.11 Moreover, migraine was characterized by a higher proportion of evening types than TTH, suggesting a greater association between migraine and circadian preference toward eveningness. These findings are particularly noteworthy given that the literature on chronotype in migraine and TTH remains limited and heterogeneous.2, 12, 13 Indeed, a recent systematic review and meta-analysis by Benkli et al. highlighted substantial variability across studies, showing that although approximately half of patients with migraine exhibit a circadian pattern of attacks, chronotype classification is highly inconsistent.2 Also, a cross-sectional study reported that patients with TTH most frequently exhibited an intermediate chronotype, followed by morning and evening types.12 Several factors may contribute to this variability, including differences in chronotype assessment methods as well as sociodemographic and clinical characteristics of the populations studied. Notably, no differences in MEQ scores were observed between patients with migraine with visual aura versus those without aura. Similarly, MEQ scores of those with migraine and TTH did not differ between participants with episodic versus chronic conditions, suggesting that chronotype may relate more to headache phenotypes than to disease chronicity. Whereas no sex differences in MEQ scores were detected among individuals with TTH, female patients with migraine exhibited lower MEQ scores than male patients.11 These findings are particularly interesting given that, although both migraine and TTH are more prevalent in females, migraine demonstrates a markedly higher female-to-male ratio (approximately 3:1) compared with TTH (approximately 1.2:1).14-16 Together, these observations raise the possibility that sex-specific circadian mechanisms may contribute to migraine susceptibility and expression, warranting further investigation into chronobiological and hormonal interactions in migraine pathophysiology. Jung and et al. further observed that anxiety and depressive symptoms varied significantly across chronotypes in both disorders, with evening types reporting the highest levels, followed by intermediate and morning types.11 Particularly in the TTH group, evening types also reported the greatest number of headache days per 30-day period, higher stress, and poorer sleep quality, with the latter finding in agreement with a previous study.12 Despite these findings suggesting that an evening chronotype may represent a vulnerability profile in which mood disorders, stress, and sleep disruption are comorbidities that converge to exacerbate headache burden, multivariable analyses adjusting for key covariates did not reveal associations between chronotype and most clinical features of migraine or TTH. The only exception was a modest positive association between MEQ scores and days with severe headaches in individuals with migraine, indicating that greater morningness is slightly associated with an increased rate of severe headache days.11 These findings underscore the complexity of circadian influences in primary headache disorders, suggesting that chronotype may be associated with vulnerability-related features such as mood, stress, and sleep disturbances, whereas its direct influence on clinical headache outcomes remains uncertain. Lastly, as noted by the authors,11 several limitations should be considered when interpreting these findings. These include the lack of data on the timing of headache attacks and the absence of information on medication use that could influence chronotype, clinical features of primary headaches, and related comorbidities. Future studies should also incorporate objective measures of chronotype classification because self-reported data may introduce bias.17 This study contributes to the limited literature and highlights chronotype as a factor to be considered in primary headache disorders. Circadian preference may influence vulnerability and clinical features of these disorders, but these effects appear to be context-dependent and intertwined with psychosocial, environmental, and biological factors. Future research integrating longitudinal designs, mechanistic studies, and chronobiology-informed interventions may help clarify the role of circadian rhythms in primary headache disorders and open new possibilities for personalized, time-of-day–sensitive management strategies. Robson C. Lillo Vizin and Caroline M. Kopruszinski declare no conflicts of interest.