Abstract
Keywords
Introduction
The relevance of timing processes is ubiquitous in medical conditions and can be traced through the millennia (1). The study of cyclical biological phenomena and disease evolution with time are relevant topics to headache medicine (2). Chronobiology-the branch of biology concerned with cyclical physiological phenomena-explains the most renowned biological rhythms —circadian cycles—, encompassing physiological and behavioral changes primarily influenced by light and darkness; ultradian rhythms, varying from minutes to less than 24 h (i.e., diurnal variations or headache appearing at a specific time of the day) and infradian rhythms (i.e., lunar phase, seasonal alterations or menstrual cycle) are relevant to headache disorders (2,3).
Accurate identification of attack duration and time of onset is essential for proper diagnosis, particularly migraine and cluster headache (CH) in line with the chronobiology-based criteria outlined in the International Classification of Headache Disorders, 3rd edition (ICHD-3) (4). Hence, a comprehensive grasp of chronobiological features holds significant implications for both education and treatment decisions (4).
However, the concept of time in headache medicine extends beyond the chronobiology of attacks, encompassing the entire disease process. Time affects biological systems, as seen in disease onset and evolution, with significant clinical implications. For example, recognition of the age of disease onset aids in diagnosis, particularly as a ‘red-flag’ for secondary headache disorders (5). Similarly, the time span in which disease progression occurs may be informative of undertreatment or due to the presence of secondary conditions. Consequently, time in terms of both the attack and disease is pivotal to multiple aspects (pathophysiology, diagnosis and treatment) of headache disorders. (6). In this review, we summarize the relevance of time in headache regarding both the attack duration and the disease characterization as well as the possible underlying pathophysiological explanations in primary headache disorders.
Methods
This is a comprehensive review focusing on the most relevant aspects of time in headache: chronobiology of attack presentation and disease evolution, considering only English-language articles published in scientific journals and chapters of English-language books. We searched the articles through Ovid MEDLINE(R) and Pubmed using the queries or a combination of the queries: ‘Migraine Disorders’, ‘Migraine’, ‘Cluster Headache’, ‘Tension Type Headache’, ‘Headache Disorders’, ‘Headache’, ‘Chronobiology Disorders’, ‘Chronobiology Phenomena’, ‘Mediators’, ‘Pathophysiology’, between 1946 and 2023. For every selected article, we first evaluated the abstract to determine its relevance to the work and then reviewed the full text. We read through the references of the articles to identify any other relevant publications. Data were organized and analyzed qualitatively.
Results
The implication of timing in attacks presentation (duration, onset in terms of circadian/infradian rhythmicity) and disease characterization (age of onset and evolution over time), as well as the possible underlying pathophysiological explanations are included in Tables 1–5 and summarized in Figure 1.

Vignette of primary headache disorders and their chronobiology. A. Chronobiology features of selected primary headache disorders. F; female, M; Male. TTH; Tension-type headache. B. Key central circadian structures and timing of attacks. Under photic stimulation, input to suprachiasmatic nucleus (SCN) directly via retinohypothalamic tract (RHT), and indirectly via intergeniculate leaflet (IGL) and geniculohypothalamic tract (GHT), ultimately SCN efferents target pineal gland (PG) via vasoactive intestinal peptide (VIP). Non-photic inputs to SCN include RN and IGL. C. Seasonal variation of primary headache bouts (stylized). Peak presentation: refers to the time of day. Created in
Attack presentation regarding duration of the main primary headache disorders.
TTH: Tension-Type Headache; CH: Cluster Headache; eTTH: episodic Tension-Type Headache; cTTH: Chronic Tension-Type Headache; –No data; Ref: references.
Attack presentation regarding onset during the day in primary headache disorders.
Abbreviations: TTH: Tension-Type Headache; CH: Cluster Headache; PET: Positron emission tomography; –No data; Ref: references.
Attack presentation regarding onset happening in bouts in primary headache disorders.
Abbreviations: TTH: Tension-Type Headache; CH: Cluster Headache; MA: Migraine with Aura. Ref: references.
Disease characterization based on age of onset of primary headache disorders.
Abbreviations: TTH: Tension-Type Headache; CH: Cluster Headache. Ref: references.
Disease characterization based on the evolution over time of primary headache disorders.
Abbreviations: TTH: tension-type headache. CH: Cluster Headache.
Attacks presentation
Attack duration
The duration of the headache attack is currently defined by the time between pain initiation and termination, which differs among primary headache disorders (4).
Migraine
The ICHD-3 states that the duration of a migraine attack ranges between 4–72 h (4). However, the average duration for treated migraine attacks ranges between 30–42 h with a large heterogenicity (7). Migraine patients suffer from longer attacks than other headache types (8). Besides that, attack duration differs regarding sex and migraine type — episodic (EM) vs chronic migraine (CM) — (7,9). Studies have shown a significantly longer attack duration in women compared to men, especially in perimenstrual migraine attacks (10). The median duration for patients with EM under 50 years old was lower in men than women, in both non-perimenstrual and menstrual attacks (7). Moreover, median headache duration was longer for patients of all ages with CM— in which it might be more difficult to define a beginning and an end of the attack due to a certain degree of continuous pain—, patients with medication overuse headache, and attacks in women, averaging 44.4 (17.9–79.0) hours. This was followed by non-perimenstrual attacks in women (7). The longer attack duration in patients with the chronic subtype may indicate that sensitization mechanisms can drive the differences in attack duration between different patient groups. Deciphering to what extent chronobiological variation as opposed to degree of sensitization contributes to duration of attacks can be difficult to elucidate, although central and peripheral mechanisms have been linked to attack duration.
At a peripheral level, it has been proposed that variations in estrogen levels during menstruation may influence attack duration in women by affecting brain excitability (11). At a central level, changes in brain function such as electroencephalography (EEG) slowing and asymmetry of the alpha frequency with a negative correlation with alpha peak frequency, and activation of anterior hypothalamic structures seen through MRI images have been associated with longer attack duration (12,13). Moreover, higher levels of vascular inflammatory markers such as pentraxin-3 (
Tension-type headache
The ICHD-3 states that the duration of tension-type headache (TTH) lasts from 30 min to seven days (4), relating to patients with episodic TTH. However, in patients with chronic TTH the duration ranges between hours to days or unremitting (4).
Regarding the pathophysiological mechanisms underlying the duration of the attacks in TTH, the literature is scarce (18,19). Treatment of the myofascial trigger point leads to reduction of the nociceptive input to the caudal trigeminal nucleus and therefore central sensitivity decreases, resulting in an improvement in TTH duration (20,21).
The presence of a TTH nocturnal onset might point towards other comorbid conditions such as sleep apnea or bruxism in which have been reported to be associated with frequent episodic TTH, without an effect on attack duration or chronobiology (22,23).
Moreover, in TTH, alpha2-adrenergic mechanisms may be the underlying pathophysiology (24). Therefore, it is plausible to hypothesize that targeting central sensitization through peripheral treatments aimed at these trigger points in TTH, along with modulation of alpha2-adrenergic mechanisms, may contribute to reducing TTH duration.
Cluster headache
Cluster headache (CH) attack duration, typically described as lasting 15–180 min (4), exhibits longer duration in women with migraine associated symptoms . However, to date, there is no clear evidence of the peripheral or central mechanisms implicated in CH attack duration.
Hypnic headache
Hypnic headache attacks last from 15 min to up to 3–4 h (4). This duration is like that of CH however, they are not associated with cranial autonomic symptoms or restlessness.
Attack onset regarding circadian rhythmicity
The onset of a headache attack refers to the moment when the first headache-associated symptoms appear. The onset of these initial symptoms may be determined by the circadian rhythm among certain primary headache disorders (4).
Migraine
Migraine attacks may follow a diurnal rhythmicity between 6:00–12:00am, although several studies have either not found a specific diurnal preference or had predominance of attacks in the early afternoon or night time (29–33). In patients over 55 years old they commonly occur during the night.
Regarding the factors underlying the diurnal rhythmicity of migraine attacks, the occurrence of environmental triggers throughout the day, such as variations of light, and the more extreme morning and evening chronotype — individual variations in preference and performance across different times of the day — (32), are associated with attack onset (35). Moreover, insomnia or sleep problems the night prior to the attack are associated with morning onset though it is unclear whether it could be a prodromal symptom . Biological mechanisms such as a morning rise in cortisol levels and a potentially different setting of the circadian pacemaker among migraineurs might play a role in diurnal rhythmicity (34). Among brain structures involved, hypothalamic activation is seen during the pre-ictal phase of migraine . The most important neuronal center for controlling the biological clock is in the hypothalamus, known as the suprachiasmatic nucleus (SCN), which helps attune the molecular clocks throughout the body based on outside stimuli such as light exposure and lifestyle. Therefore, circadian rhythmicity in migraine patients is influenced by triggers, chronotype and hypothalamic activation, correlating with the timing of migraine attacks.
Tension-type headache
In TTH no time preference of headache attack has been identified nor linked to chronotype . Moreover, limited circadian data exist . In short, the mechanism of the chronobiology of the TTH attack has not yet been elucidated.
Cluster headache
In patients with CH attacks that occur at night, generally between 9pm and 2am which can be detected by actigraphy, they have a more specific pattern compared to migraine (38,–41). Moreover, in patients with CH daytime naps, nocturnal sleep and lay down after a stressful situation have been reported as triggers, pointing towards the hypothalamus governing the attack biology, especially in patients noting diurnal rhythmicity that reported sleep as an attack activator (42). Therefore, concerning the pathophysiological mechanisms underlying CH, the suprachiasmatic nucleus (SCN) plays a key role in adjusting the circadian clock to consider fluctuations exhibited in light received by the retina (43). Cluster headache (CH) is associated with REM sleep, often occurring 90 min after sleep onset, coinciding with the first REM phase and linked to orexinergic system fluctuations (6). A Positron emission tomography (PET) study revealed CCH patients in active pain state compared to control patients had activation in the ipsilateral inferior hypothalamic grey matter (44). Although migraine also has hypothalamus involvement, it is believed to be one of the key factors regarding circadian rhythm in CH. Regarding other mediators and genes involved in headache onset, a number of studies explored genes identified to have a role in circadian rhythm, namely,
Hypnic headache
Headaches occur at least four nights/week, usually at a consistent time each night (4).
Attacks onset regarding infradian rhythmicity
The initiation of a headache bout is the time when the first attack of a group of attacks occurs. Attack onset may be determined by the infradian rhythm among certain primary headache disorders (4).
Migraine
In addition to diurnal rhythms, infradian rhythms characterized by seasonal variation also play a role in the frequency and severity of migraine attacks and disease progression . The seasonal fluctuation in attack frequency might be attributable to changes in the presence of attack triggers (stress/work) throughout the year . Moreover, a higher incidence of migraine with aura attacks during light seasons has been reported, highlighting a potential connection to light variations as well as with temperature . Besides that, pure menstrual migraine with or without aura occurring in a predictable pattern exclusively in the perimenstrual period (from −2 to +3 days), and menstrual-related migraine with or without aura occurring both perimenstrual and at other times of the menstrual cycle also highlight the importance of the infradian rhythmicity in migraine (4).
Regarding the underlying pathophysiological mechanisms, the brain structures involved in migraine, specifically the sensitivity of the hypothalamus to light and behavior also provides a strong connection to seasonal variability. The pathophysiology of menstrual migraine is thought to be primarily linked to hormonal fluctuations, especially the decline in estrogen levels preceding menstruation which modulates pain perception and inflammatory responses resulting in a heightened sensitivity to migraine triggers. This sensitivity can lead to the activation of various pathways in the brain associated with migraine attacks, such as cortical spreading depression and trigeminovascular system activation (4). Therefore, seasonal variations influence migraine frequency likely due to changes in trigger presence such as stress and light exposure but also due to hypothalamic sensitivity to light and brain structures involved in migraine and hormonal changes implicated in these infradian rhythms.
Tension-type headache
The evidence supporting the cyclic nature of tension-type headaches remains insufficient. To date, the relationship between infradian rhythmicity and TTH evolution is unknown.
Cluster headache
In CH, attacks occur with an infradian circannual pattern as they follow the same onset pattern annually, especially during spring and autumn with the lowest reported CH bouts in summer (39,41,57). Photoperiodism, changing of daylight length, and bouts tend to occur based on daylight patterns annually (57). Fluctuations in daylight length have been shown to increase the onset of cluster period, shortly succeeding the longest and shortest days of the year (70). Climate conditions and patterns had a differing effect on cluster periods. Previous cold or warm periods may shape the onset of cluster attacks (70). Moreover, patients tend to report cluster bouts during November and fewer occurrences of cluster during the summer months, with greater daylight (42). Additionally, some evidence shows that there are greater CH populations further away from the equator (71). This further alludes to the influence of daylight hours in the prevalence of cluster and thus, the circadian rhythm is pivotal in the involvement of CH pathophysiology (72).
In CH, in the anterior section of the hypothalamus, the SCN, a detection of increased grey matter volume, ipsilaterally, was recognized in episodic CH (eCH) and chronic CH (CCH) studied patients, compared to the control group, further indicating and giving rise to the circannual phenomenon in CH (73). Apropos the SCN, its relationship with light offers interesting information. Illumination passing through the retina influences the SCN (74). Light is detected via cone and rod photoreceptors Furthermore, intrinsically photosensitive retinal ganglion cells (ipRGCs), which are sensitive to blue light further detect external light and transmit signals through the retinohypothalamic (RHT) tract to the SCN (74). After light signals have been received, SCN neurons are activated and thus, induce the expression of clock genes
Among mediators, lower vitamin D is prevalent amongst CH patients with attacks from Winter to Spring (58) although no correlation has been found between CH and three SNPs in vitamin D receptor gene (58).
The characteristics of the attack regarding duration and time onset and bouts, as well as possible pathophysiological explanations underlying specific duration of the attacks are included in Tables 2 and 3.
Disease characterization
Age of onset
Migraine
The one-year prevalence of migraine is 15% in the general population, with a female-to-male ratio of 3:1 (76). Half of migraine patients report migraine onset before the age of 25 (median age of onset of 25 years in women and 24 years in men) (59). There is an association of early onset with higher attack frequency in the long-term, so it is considered a negative prognostic factor (77). Migraine prevalence rates increase in girls from puberty onward (78). Although the specific interplay and mechanisms between hormones and the age of migraine onset are complex and incompletely understood, there is evidence that hormonal factors, especially estrogen fluctuations, may influence migraine onset and remission (79). Moreover, migraine has a strong familial aggregation, with twin and family studies estimating its heritability at 35%- 60% (80).
Tension-type headache
The one-year prevalence of episodic TTH and chronic TTH is estimated at 38- 85%, and 0.9–2.2%, respectively and the peak prevalence is estimated at age 35–39 (81,82). Age of onset does not seem to differ between men and women (60) while TTH prevalence tends to be slightly higher in women with a female-to-male ratio of 1.2:1 (83). This points to a lower influence of hormones in TTH compared to migraine.
According to two twin studies, the heritability of TTH varies with the presence of concomitant migraine, with a higher heritability in those without concomitant migraine (84). However, in contrast to genetic research on migraine, specific genes predisposing to TTH are unknown, and age of onset in relation to family history has not been studied so far. However, an onset at > 50 years of age is considered a red flag for secondary headache, similarly to other primary headache conditions (83).
Cluster headache
The one-year prevalence of CH is estimated at 53 per 100,000 and males are predominantly affected with the overall sex ratio being 4:1 (male to female) (61). Numerous studies have reported mean age of onset, ranging from 27.2 to 33.9 years (85,86). Age of onset is younger for episodic than for chronic CH and tends to be younger in men (61). Reported age of diagnosis shows 6–9 years of delay from age of onset (85).
Family and twin studies have long suggested a genetic basis of CH, which has been confirmed by recent Genome-wide association studies (GWAS) analyses (49,50); whether genetic determinants influence the age of onset of CH still needs to be investigated.
Several studies indicate a high prevalence of cigarette smoking in CH patients, linking smoking history to an earlier age of onset (87). A Korean study reported a significantly lower age at onset in the never-smoker group compared to the ever-smoker group (27.1 ± 12.9 vs. 30.6 ± 10.9, p = 0.024) (87). An analysis from the United States Cluster Headache Survey indicated that patients without tobacco exposure were significantly more likely to develop CH at ages 40 and younger, while the exposed sufferers were significantly more likely to develop CH at 40 years and older (88). This suggests that patients developing CH at younger age without tobacco exposure have a more innate genetic susceptibility, while in patients developing CH at an older age, toxicity of tobacco exposure altering hypothalamus-based neurotransmitter function might play a more important pathophysiological role (87,88). Table 4 includes disease characterization based on age of onset.
Evolution of primary headache disorders
Migraine
The characteristics and clinical features of migraine vary with age (7,62). The duration of migraine attacks in children is shorter than in adolescents and adults, often bilateral, and accompanied by vomiting and nausea (62). Children with migraine are more likely to have experienced infantile colic than those without migraine (73% vs. 27%) (89). Longitudinal studies of 10 to 25 years in pediatric migraine show a decrease in frequency, duration, and intensity of attacks with a remission rate of 14–35% during the follow-up period (64,65). As individuals transit from adult to elderly lesser migraine features and better functioning during headache attacks are observed (63). Moreover, the patterns of headaches may shift slightly towards the back of the head or exhibit more bilaterally, as well as happening at night (90) or having headache with TTH features (8,65,66). Additionally, the emergence of migraine onset during the night appears to be an age-related feature, appearing in the course of the disease (30).
In migraine, natural rhythms appear to worsen as the disease becomes chronic in some patients, losing the pattern, and conversely, when properly treated, they improve and there is a lower incidence of attacks, possibly causing an epigenetic regulation of these regulatory centers (91).
Tension-type headache
During childhood, the prevalence of tension type headache varies highly depending on age. The prevalence increases with age, 6–38% in preschoolers, 38–50% in school aged children and 75% in adolescents (92). However, there are no differences between children and adolescents in frequency, intensity, laterality, characteristics of pain (67). After the peak prevalence at 30–39 years, the frequency of TTH tends to decrease as age increases (93). They typically present with bilateral and moderate intensity, lacking distinct features. It is known that TTH exhibits a higher remission rate than migraine as individuals transition from adolescence to adulthood (90).
Cluster headache
A long-term follow-up of untreated patients showed decreased CH features including side-locked unilaterality, autonomic symptoms and diurnal rhythmicity and 33% remission at mean age of 42.3 years (range of 27–65) (68).
Other primary headaches
Although only limited data were available for evolution of other primary headaches, most showed a high remission rate over time (Table 5).
Importance of time in headache: Therapeutics and research
A detailed understanding of chronobiology is required to both accurately phenotype and diagnose primary headache disorders, and aid in the identification of secondary pathologies. As described in Tables 1–4, timing is both critical in positive diagnosis and consideration of ‘red-flags’ (5). In eCH, an understanding of the circannual pattern will not only reduce treatment burden, but modelling periods of chrono-risk may also provide the opportunity for precision management (6). Moreover, understanding the natural evolution of migraine allows us to tailor therapy to an individual's age.
Time may also have an impact on the efficacy of therapy in migraine. In a randomized trial of exercise in migraine, synchrony of the timing of the intervention with exercise performance determined efficacy (94). There are conflicting clinical reports on the impact of timing of onabotulinumtoxinA injection on efficacy (95,96). The relationship between chronobiology and efficacy of therapy is largely unexamined in trial design. Moreover, “Time is brain,” advocating for prompt migraine treatment, leads to better outcomes. Earlier triptans use and shorter CM durations predict better acute and positive onabotulinumtoxinA responses (97,98). Additionally, the APPRAISE trial showed that early erenumab treatment in EM yields enhanced, lasting efficacy and better safety and adherence compared to standard oral preventatives (99).
Finally, chronobiology is pivotal in research (Table 6). Genetic studies have identified
Summary of attack rhythmicity, age of onset, evolution and possible pathophysiology in prevalent primary headache disorders.
Abbreviations: TTH: Tension-Type Headache. CH: Cluster Headache.
Conclusions
The exploration of time in headache disorders unveils intricate patterns intertwined with the attack and disease evolution in primary headaches. From the diurnal rhythms guiding migraine attacks to the circannual fluctuations defining CH bouts, understanding these temporal intricacies is indispensable for accurate diagnosis, tailored treatment, and precision management. In fact, the use of preventive treatments which help to restore these timing processes in headache disorders should not be delayed.
This comprehensive review underscores the significance of time in headache in primary headache disorders unraveling their pathophysiological underpinnings. As we delve deeper into the timing processes of headaches, novel insights emerge, offering promising avenues for improved clinical research designs and personalized therapeutic interventions, which may enhance efficacy and precision in our approach to patient care, marking a significant advancement in headache management.
Clinical implications
The exploration of chronobiology reveals intricate patterns in attack duration, onset, disease age of onset, and evolution in primary headaches, from diurnal rhythms guiding migraine attacks to circannual fluctuations defining cluster headache bouts.
Migraine attacks exhibit significant diurnal and infradian rhythms, influenced by melatonin levels, light sensitivity, and hypothalamic activation; several gene polymorphisms have been associated with migraine attack duration.
Tension-type headache lacks clear chronobiological patterns, with limited understanding of its underlying mechanisms.
Cluster headache displays a distinct circannual pattern, with attacks often occurring at night and relevant involvement of the hypothalamus.
Understanding temporal intricacies is indispensable for accurate diagnosis, tailored treatment, and precision management in primary headache disorders.

