Migraine and tension-type headache in Croatia: a population-based survey of precipitating factors

The careful monitoring of the trigger factors of headache could be an important step in treatment, because their avoidance may lessen the frequency and severity of attacks. Furthermore, they may provide a clue to the aetiology of headache. The aim of the present study was to estimate the prevalence of tension-type headache (TTH) and to establish the frequency of precipitating factors in subjects with migraine and TTH in the adult population of Bakar, County of the Coast and Gorski Kotar, Croatia. Another important purpose of the study was to examine the relationship of the precipitating factors with migraine and TTH, and with migraine subtypes: migraine with aura (MA) and migraine without aura (MO). We performed a population-based survey using a 'face-to-face door-to-door' interview method. The surveyed population consisted of 5173 residents aged between 15 and 65 years. The 3794 participants (73.3%) were screened for headache history according to the International Headache Society (IHS) criteria. Headache screen-positive responders, 2475 (65.2%), were interviewed by trained medical students with a structured detailed interview focused on the precipitating factors. The following precipitating factors in lifetime migraineurs and tension-type headachers have been assessed: stress, sleep disturbances, eating habits, menstrual cycle, oral contraceptives, food items, afferent stimulation, changes in weather conditions and temperature, frequent travelling and physical activity. A total of 720 lifetime migraineurs and 1319 tension-type headachers have been identified. The most common precipitants for both migraine and TTH were stress and frequent travelling. Stress (odds ratio (OR) 1.4, 95% confidence interval (CI) 1.17, 1.69) was associated with migraine, whereas physical activity (OR 0.72, 95% CI 0.59, 0.87) was related to TTH. Considering MA and MO, frequent travelling (OR 2.2, 95% CI 1.59, 2.99), food items (OR 2.2, 95% CI 1.35, 3.51) and changes in weather conditions and temperature (OR 1.75, 95% CI 1.27, 2.41) exhibited a significant positive association with MA. The present study demonstrated that precipitant-dependent attacks are frequent among both migraineurs and tension-type headachers. Lifetime migraineurs experienced headache attacks preceded by triggering factors more frequently than tension-type headachers. MA was more frequently associated with precipitating factors than MO. We suggest that some triggering factors may contribute to the higher occurrence of precipitant-dependent headache attacks in susceptible individuals.     

A community-based study of headache diagnosis and prevalence in Singapore

We present the results of a community survey based on the diagnostic criteria of the International Headache Society (IHS) describing headache prevalence and symptomatology in the Singapore population. A questionnaire administered by trained personnel was completed by 2096 individuals from a randomized sample of 1400 households. The overall lifetime prevalence of headache was 82.7%. The migraine prevalence was 2.4% in males and 3.6% in females; for episodic tension-type headache and chronic tension-type headache the corresponding figures were 11.1%/11.8% and 0.9%/1.8%, respectively. Inclusion of borderline cases (IHS codes 1.7 and 2.3) resulted in prevalences of 9.3% for migraine, 39.9% for episodic tension headache and 2.4% for chronic tension headache. Headaches described by 31.2% of the respondents were unclassifiable. The different premonitory symptoms, precipitants and aggravating factors in migraine and tension-type headache in our study population suggest that they represent two distinct syndromes rather than opposite ends of a clinical spectrum.     

Precipitating factors of headache. A prospective study in a national control-matched survey in migraineurs and nonmigraineurs

Prospective studies of precipitating factors in migraine are rare. Mig Access is a national control-matched survey conducted to evaluate the access of migraineurs to health care in France. This study allowed us to screen prospectively some precipitating factors of headache in migraineurs and in nonmigraineurs. Three hundred eighty-five migraineurs (group 1) and 313 nonmigraineurs (group 2) kept a diary for a 3-month period (a total of 35,805 day in group 1 and 29,109 days in group 2). Precipitating factors were reported for each headache period. Headache intensity was self-assessed during each headache period using a visual analog scale of 0 to 100. Headache was reported on 4274 days (12%) in group 1 and on 602 days (2%) in group 2. Headache intensity was greater in group 1 (39 +/- 20 versus 32 +/- 19, P < .05). The most frequent precipitating factors (reported at least once by more than 10% of subjects [range 18% to 80%] in both groups) were fatigue and/or sleep, stress, food and/or drinks, menstruation, heat/cold/weather, and infections in both groups. All these factors except infections were reported to cause headache more frequently in migraineurs than in nonmigraineurs. Mean intensity of headache related to fatigue and/or sleep, stress, food and/or drinks, hot/cold weather, and menstruation varied from 37 to 43 in migraineurs and from 29 to 35 in nonmigraineurs. Headache with the highest mean intensity was due to infections in the two groups (47 +/- 20 in group 1, 45 +/- 23 in group 2). Our results support that endogenous factors are the most frequent triggers of headache in migraineurs. The most frequent precipitating factors of headache appear identical in migraineurs and in nonmigraineurs. Our results suggest that similar triggers could precipitate headache of different type in these two populations.     

Kinesiophobia in migraine.

Pain aggravation by movement and avoidance of movement (kinesiophobia) is often reported by patients during migraine attacks. Yet its specific contribution to migraine diagnosis is undetermined. To characterize the frequency and severity of kinesiophobia during migraine and its role in the diagnosis of primary headaches, we questioned 150 patients (126 women and 24 men, average age 38.5 yrs) with migraine (n = 111) or tension-type headache (TTH) (n = 39) about aggravation of pain by bending forward, brisk head movements (jolt), and avoidance of movement during the attacks. The degree of pain worsening by each stimulus was measured through a visual analog scale and compared to worsening produced by other sensory stimuli such as light, sound, and smell. The discrimination power of kinesiophobia between migraine and TTH was calculated, using the International Classification of Headache Disorders criteria as gold standard. Sensitivity/specificity of studied symptoms was high in differentiating the 2 headache types: bending forward: 98%/85.7%; jolt: 96.3%/81.6%; and immobility during the attacks: 100%/70%. The degree of kinesiophobia was identical to photo- and phonophobia in migraine patients. We conclude that kinesiophobia discriminates between migraine and TTH. Bending forward and jolt may be useful additional questions to ask patients for the differentiation of headache attacks. PERSPECTIVE: This article evaluates the specific role of movement (movement-induced pain aggravation and avoidance of movement) in primary headaches. Kinesophobia is an easy symptom to screen, explained by migraine pathophysiology, and proved to be a sensitive and specific measure to identify migraine attacks when compared to tension-type headache.     

Menstrual tension-type headache: evidence for its existence

OBJECTIVE: To determine whether menstrual tension-type headache is a real disorder. BACKGROUND: An appendix was included in the second edition of the International Classification of Headache Disorders by the International Headache Society. Diagnostic criteria are proposed in this appendix for 2 types of menstrual migraine: pure menstrual migraine without aura and menstrually related migraine without aura. References to menstrual tension-type headache do not appear in this classification. METHODS: In a neurological outpatient clinic 165 patients were identified in whom headache was related to menstruation and the criteria of the International Classification of Headache Disorders for menstrual migraine adapted to menstrual tension-type headache were applied. RESULTS: Twenty-one patients met the criteria of menstrual tension-type headache, 6 for pure menstrual tension-type headache, and 15 for menstrually related tension-type headache. CONCLUSION: Menstrual tension-type headache is a real condition that should be recognized in the International Classification of Headache Disorders.     

Quantitative Assessment of the Tension-Type Headache and Migraine Severity Continuum

Two quantitative measures for Waters'¹ tension-type head ache and migraine severity continuum are proposed. To ensure face validity, symptoms and precipitants of this disorder were compiled from the literature as a basis for the Auckland Migraine and Headache Inventory. This inventory was completed by 84 participants (mean age ± SD, 26.0 ± 9.7 years; range, 18 to 59 years) who complied with the criteria of the International Headache Society, for migraine of tension-type headache. The migraine headache index and the number of precipitants were derived from the Auckland Migraine and Headache Inventory. These scores yielded significant internal reliability ( r _s =.77 and .84), test-retest reliability ( r _s =.86 and .74), and concurrent validity ( r _s =.57) coefficients. The data, therefore, support the notion that the migraine headache index and the number of precipitants are reliable and valid indices of tension-type headache and migraine severity, suitable for participant selection and assessment of treatment. This study offers support for Waters'1 suggestion that tension-type headache and migraine are extremes of a severity continuum.     

Osmophobia in migraine and tension-type headache and its clinical features in patients with migraine

Intolerance to smell is often reported by migraine patients. This study evaluates osmophobia in connection with the diagnosis of migraine and episodic tension-type headache (ETTH). The characteristics of this symptom are also investigated. We recruited from our Headache Centre 1005 patients (772 female, 233 male; age 37 +/- 11 years), of whom 677 were migraine without aura (MoA), 130 migraine with aura (MA) and 198 TTH. Patients with two or more forms of primary headache were excluded. Among migraine patients, 43.9% with MoA and 38.5% with MA reported osmophobia during the attacks; none of the 198 TTH patients suffered this symptom. Most frequently offending odours were scents (63.9%), food (55.2%) and cigarette smoke (54.8%). Osmophobia appears structurally integrated into the migraine history of the patient. It seems to be a peculiar symptom favouring the diagnosis of migraine (MoA and MA) in the differential diagnosis with ETTH.     

American Headache Society members' assessment of headache diagnostic criteria

OBJECTIVE: We assessed the views of physicians interested in headache as to the diagnosis of the most commonly occurring and currently controversial headaches. BACKGROUND: The International Headache Society (IHS) classification system has received wide professional endorsement and considerable empirical support, but in the United States, their adoption by clinicians may be proceeding more slowly. Questions remain, including what diagnostic criteria for migraine and tension-type headache clinicians may continue to favor over those outlined by the IHS, to what extent is the "transformed migraine" diagnosis used in clinical practice, and how is analgesic rebound headache diagnosed with regard to the various quantitative measures of analgesic use. METHODS: Members of the American Headache Society rated the importance of IHS and non-IHS diagnostic criteria for migraine and tension-type headache and for analgesic rebound headache. Respondents also described their use of the proposed transformed migraine diagnosis. RESULTS: Two-thirds (67.3%) of the respondents reported use of the IHS criteria or the IHS criteria in conjunction with clinical judgment. For migraine and tension-type headache, IHS criteria were rated with high importance, but some respondents reported using additional non-IHS diagnostic criteria and de-emphasizing certain IHS criteria. For chronic headache, almost two-thirds (63%) of respondents reported using the transformed migraine diagnosis. For analgesic rebound headache, respondents preferred to make the diagnosis based on medication consumption that is lower than amounts stipulated in the IHS classification system. CONCLUSIONS: There remains a number of physicians interested in headache who do not use the IHS classification system, who modify the IHS criteria in practice, and who use the "transformed migraine" diagnosis for patients with chronic daily headache.     

2000 Wolfe Award. Sumatriptan for the range of headaches in migraine sufferers: results of the Spectrum Study

BACKGROUND: Migraineurs experience a spectrum of headaches: migraine, migrainous, and episodic tension-type as defined by the International Headache Society (IHS). OBJECTIVE: To evaluate the effectiveness of sumatriptan, 50-mg tablets, in treating the spectrum of headaches in IHS-diagnosed migraineurs. DESIGN/METHODS: Migraineurs with severe disability (Headache Impact Questionnaire score 250 or greater) were enrolled in a randomized, double-blind, placebo-controlled, crossover study. Patients treated up to 10 headaches with sumatriptan, 50 mg, or placebo (4:1). Headache features, recorded prior to treatment, were used to classify each headache using IHS criteria. Headache response (moderate or severe pain reduced to mild or no pain) and pain-free response were recorded at 2 and 4 hours postdose (primary endpoint). Because patients treated multiple attacks, statistical methods controlling for within-subject correlation were used. RESULTS: Two hundred forty-nine migraineurs treated 1576 moderate or severe headaches: migraine (n = 1110), migrainous (n = 103), and tension-type (n = 363). Sumatriptan was superior to placebo for headache response 4 hours postdose (primary endpoint) across all headache types (migraine, 66% versus 48%; P<.001; migrainous, 71% versus 39%; P<.01; tension-type, 78% versus 50%, P<.001). Sumatriptan was also superior to placebo for pain-free response 4 hours postdose for migraine (41% versus 24%, P<.001) and tension-type headaches (56% versus 36%, P =.001). Sumatriptan provided superior pain-free response 2 hours postdose for migraine (18% versus 7%, P<.0001) and tension-type headache (28% versus 14%, P =.0005) compared with placebo. CONCLUSION: Sumatriptan, 50-mg tablets, are effective for the full spectrum of headaches experienced by patients with disabling migraine due to a sumatriptan-responsive mechanism.     

Characteristics of headache in migraine without aura and episodic tension-type headache in the Turkish population according to the IHS classification

We evaluated the characteristics of headache in migraine without aura and episodic tension-type headache diagnosed according to the International Headache Society (IHS) Classification. Fifty migraine without aura and 50 tension-type headache patients were selected prospectively. Fifty-eight percent of migraineurs had pain of a pulsating quality; 88% had severe pain and 74% had unilateral pain; aggravation by routine physical activity was reported by 96%. Episodic tension-type headache was of a pressing quality in 52%, moderate in 40%, bilateral in 82% and aggravated by routine physical activity in 16%. Nausea and/or vomiting, photophobia and phonophobia were reported significantly more commonly in migraineurs than tension-type headache patients.     

The global burden of headache: a documentation of headache prevalence and disability worldwide

This study, which is a part of the initiative 'Lifting The Burden: The Global Campaign to Reduce the Burden of Headache Worldwide', assesses and presents all existing evidence of the world prevalence and burden of headache disorders. Population-based studies applying International Headache Society criteria for migraine and tension-type headache, and also studies on headache in general and 'chronic daily headache', have been included. Globally, the percentages of the adult population with an active headache disorder are 46% for headache in general, 11% for migraine, 42% for tension-type headache and 3% for chronic daily headache. Our calculations indicate that the disability attributable to tension-type headache is larger worldwide than that due to migraine. On the World Health Organization's ranking of causes of disability, this would bring headache disorders into the 10 most disabling conditions for the two genders, and into the five most disabling for women.     

Factors associated with burden of primary headache in a specialty clinic

OBJECTIVE: To examine factors associated with social, occupational, and psychological burden of common primary headache (migraine and tension-type headache). BACKGROUND: The personal and social burden of primary headache is high. Health, occupational, social, and psychological factors contributing to burden in people with disabling headache have not been fully unravelled. METHODS: One hundred eighty consecutive patients with either migraine or tension-type headache attending a specialty headache outpatient clinic for the first time were evaluated over a 9-month period. Headache subtype was operationally defined according to International Headache Society criteria. Headache frequency, duration, and severity were recorded. Occupational and social disability were quantified using the Migraine Disability Assessment questionnaire. Psychological burden was quantified using the 28-item General Health Questionnaire, the Beck Depression Inventory, and the State-Trait Anxiety Inventory. Premorbid vulnerability to life stress was quantified using the neuroticism subscale of the Eysenck Personality Inventory. RESULTS: Patients with frequent (chronic) headache scored higher on the Migraine Disability Assessment questionnaire and had higher Beck Depression Inventory and General Health Questionnaire depression scores than those with less frequent (episodic) headache. Frequency of headache, but not pain severity, duration, or diagnosis, predicted both Migraine Disability Assessment total disability and General Health Questionnaire/Beck Depression Inventory depression. Neuroticism was predictive of depression but not disability. Patients with chronic migraine had the highest depression and disability scores. CONCLUSION: The number of days per month with headache is a key determinant of headache-related burden in those attending specialty clinics. Frequent (chronic) headache is associated with significantly higher psychopathology scores and general social impairment, but the direction of this relationship is not clear. Those with migraine and chronicity are the most impaired.     

Psychosocial factors in children and adolescents with migraine and tension-type headache: a controlled study and review of the literature

We investigated 341 children and adolescents to evaluate the relevance of psychosocial factors in idiopathic headache. According to the criteria of the International Headache Society, 151 subjects had migraine and 94 had tension-type headache (TTH). Ninety-six subjects were headache-free controls. Psychosocial factors covered family and housing conditions, school problems, relations in the peer group, and several other items. We found that migraine patients did not differ from headache-free controls. Patients with TTH more often had divorced parents than the headache-free controls, and they had fewer peer relations than migraineurs and controls. In addition, migraine patients were significantly more often absent from school due to headache. All other psychosocial factors failed to discriminate between the three study groups. In conclusion, this controlled study in children and adolescents suggests that migraine is not related to family and housing conditions, school situation, or peer relations, whereas TTH is associated with a higher rate of divorced parents and fewer peer relations.     

Prevalences of migraine and tension-type headache in adolescent girls of Shiraz (southern Iran)

OBJECTIVE: To determine the prevalences of migraine and tension-type headache in teenaged girls attending schools in Shiraz (southern Iran). BACKGROUND: Studies of headache prevalence are numerous, and findings have varied according to the specific population and region involved. No data are available regarding headache prevalence among Iranian teenagers. METHODS: A random sample of 1868 teenaged girls (aged 11 to 18 years) was evaluated, and 507 subjects reported headache. The headache disorders were classified on the basis of a clinical interview, general physical and neurologic examinations, and the diagnostic criteria of the International Headache Society. Logistic regression was used for data analysis. RESULTS: Overall prevalence rate for migraine was 6.1% (95% CI, 5.0 to 7.2) and for tension-type headache, 12.1% (95% CI, 10.6 to 13.6). Migraine and tension-type headache were significantly associated. CONCLUSIONS: It is concluded that exposition of subjects to sunlight, type of food, and a family history of headache had most significant effects on occurrence of migraine and tension-type headaches.     

Classification of Daily and Near-Daily Headaches: Proposed Revisions to the IHS Criteria

SYNOPSIS
The International Headache Society (IHS) headache classification, while a major advance, does not adequately classify the daily and near-daily headache disorders known as chronic daily headache (CDH). We believe that chronic daily headache is a group of disorders which includes chronic tension-type headache (CTTH), transformed migraine (TM), new daily persistent headache (NDPH), and hemicrania continua (HC). We propose specific criteria for transformed migraine, new daily persistent headache, and hemicrania continua, and have modified the criteria for chronic tension-type headache.     

Use of cluster analysis to validate IHS diagnostic criteria for migraine and tension-type headache

Cluster analysis was used to validate headache diagnostic criteria of the International Headache Society (IHS). Structured diagnostic interviews were conducted on 443 headache sufferers from a community sample, which was randomly split to allow replication. Hierarchical cluster analysis of symptoms in both subsamples revealed two distinct ( P <.001) clusters: (1) unilateral pulsating pain, pain aggravated by activity, and photophobia and phonophobia, and (2) bilateral pressing/tightening pain, mild to moderate intensity, and absence of nausea/vomiting. These clusters were consistent with IHS migraine and tension-type classifications, respectively. Replication using a non-hierarchical clustering technique, k-means cluster analysis, revealed a migrainelike patient cluster, reflecting more frequent pulsating, unilateral pain; more severe pain; and pain aggravated by activity; nausea, vomiting, photophobia, and phonophobia. A tensionlike patient cluster was also identified, reflecting more frequent pressing/tightening pain, mild to moderate pain, bilateral location, and absence of nausea/vomiting. These patient clusters were consistent across subsamples. International Headache Society diagnoses corresponded with classification based upon statistically derived clusters ( P <.001). These results indicate that headache symptoms cluster empirically in a manner consistent with IHS criteria for migraine and tension-type headaches. Criterion overlap problems regarding pain intensity and duration were identified. Overall, these data support migraine and tension-type headache as distinct entities, and provide support for the IHS diagnostic criteria with minor modifications.     

Lifetime prevalence and characteristics of recurrent primary headaches in a population-based sample of Swedish twins

OBJECTIVE: To examine the lifetime prevalence and other characteristics of recurrent primary headaches in twins. BACKGROUND: The twin model may provide insights into the role of genetic and environmental influences in headache disorders. However, assumptions as to whether twins are representative of the general population, and whether monozygotic and dizygotic twins are similar have rarely been addressed. METHODS: The study population consisted of a random sample of 17- to 82-year-old twins from the Swedish Twin Registry (n = 1329). Structured interviews on the telephone by lay personnel and the International Headache Society criteria were used for assessment and diagnosis of recurrent primary headaches. Prevalence data of the general population for migraine and tension-type headache was obtained from various published reports. RESULTS: A total of 372 subjects (29%) had ever had recurrent headaches. In total, 241 recurrent headache sufferers fulfilled the criteria for migraine or tension-type headache, and the lifetime prevalence was 7.1% for migraine without aura, 1.4% for migraine always with aura, 1.9% for migraine occasionally with aura, 9.4% for episodic tension-type headache, and 1.3% for chronic tension-type headache. The lifetime prevalence of all migraine and all tension-type headache, including another 84 subjects fulfilling all but one of the criteria for migraine or tension-type headache, was 13.8% and 13.5%, respectively. The corresponding prevalence risk for women was 2.4 (95% confidence interval [CI] 1.7, 3.4) and 1.5 (95% CI 1.1, 2.1), respectively. Zygosity was not a significant predictor for migraine. In tension-type headache, the prevalence risk for dizygotic twins and unlike-sexed twins as compared with monozygotic twins was 1.9 (95% CI: 1.2, 3.1) and 1.8 (95% CI: 1.1, 2.9), respectively. CONCLUSION: There is no twin-singleton or monozygotic-dizygotic difference for the risk of migraine. In tension-type headache, twins seem to have a lower risk than singletons, and this is especially true for monozygotic twins.     

Weekend headache: a retrospective study in migraine without aura and episodic tension-type headache

Our retrospective study was aimed at determining the existence of weekend headache and, if so, whether it has the same clinical features as migraine without aura and episodic tension-type headache, or whether it occurs as a separate form of headache which could find its own place in the International Headache Society classification.
For this study, we reviewed the clinical records of 120 patients with migraine without aura and 120 patients with episodic tension-type headache randomly selected among all those referred to the Headache Center of the University of Parma Institute of Neurology between 1985 and 1996.
A review of these records suggests that weekend headache exists for both types of headache considered. Clinically, it is interesting to note that the male-to-female ratio for the weekend form of tension-type headache was 1:1, as opposed to 1:3 for general episodic tension-type headache. As regards classification, no evidence so far seems to suggest that weekend headache should be considered as an independent entity. Apart from certain features that appear to be peculiar to this form of headache—such as increased pain intensity—it thoroughly fulfills the diagnostic criteria of the primary headaches from which it evolves. Finally, a few clinical features suggest that the weekend may simply be a triggering factor in migraine without aura attacks, while playing a major role in episodic tension-type headache. However, weekend headache is a clinical entity that clearly needs further study.     

Classification of chronic daily headache by International Headache Society criteria: limits and new proposals

We conducted a retrospective study of 150 patients with chronic daily headache (CDH) to determine how to categorize their headache according to the classification of the International Headache Society (IHS). All patients were first evaluated at Parma and Pavia Headache Centres (from January 1992 to March 1993) and had had headache for at least 15 days a month during the previous 6 months. Four patients were thereafter excluded due to poor reliability. The 146 patients who met our CDH criteria (92 with and 54 without clear-cut migraine attacks) could be classified into four groups: (i) chronic tension-type headache (CTTH)-27 patients; (ii) coexisting migraine plus CTTH-65 patients; (iii) unclassifiable daily headache-27 patients; and (iv) migraine and an unclassifiable interval headache-27 patients. Seventy-two percent of patients with CDH had migraine as the initial form of their headache. We therefore propose to revise the IHS classification for migraine, taking into account its evolution, and add two subcategories, migraine with interparoxysmal headache and chronic migraine.     

Headache induced by chronic substance use: analysis of medication overused and minimum dose required to induce headache

BACKGROUND: The International Headache Society has defined the diagnostic criteria for headache induced by substance use. Recently, a revision to these criteria has been proposed. OBJECTIVE: To consider whether the International Headache Society criteria for headache induced by substance use and the proposed revisions for the classification of daily and near-daily headache with medication abuse permit classification of patients commonly seen in a headache center. METHODS: One hundred fourteen consecutive patients (96 women [84.2%] and 18 men [15.8%]; mean age, 54.2 years [SD, 14]) with headache and chronic overuse of medications, admitted for detoxification to the inpatient unit of a headache center, participated in the study. The initial headache, medications and doses used, duration of daily medication use, and means of medication administration were studied. RESULTS: Eighty-one patients (71%) had an initial headache of migraine without aura, 13 patients (11.4%) had migraine without aura and coexistent tension-type headache, 11 (9.7%) patients had migraine with and without aura, and 9 patients (7.9%) had episodic tension-type headache. Medications overused by patients included analgesics combined with barbiturates or other nonnarcotic substances in 39.5%, simple analgesics in 38.6%, triptans in 11.4%, and ergotamine in 10.5%. Using the International Headache Society diagnostic criteria, we were able to classify only 28.1% of our patients; the proposed revised criteria for daily and near-daily headaches with medication abuse permitted the classification of 46.4% of patients. CONCLUSION: The minimum dose of medication required to induce chronic headache should be revised because a high proportion of patients are not classifiable using either the International Headache Society diagnostic criteria or the revised criteria recently proposed. A more comprehensive definition for the required minimum dose might be used. Triptan abuse can cause chronic headache and should be included in the International Headache Society classification.