The outcome included the prevalence of migraine, tension-type headache, cluster headache, and other headache types, stratified by age (19–29, 30–39, 40–49, 50–59, and ≥ 60 years old) and sex (male or female). The headache type and its probable cases were classified based on the questionnaire responses including internal diagnostic criteria according to ICHD-3 ; Additional files 1–3). Individuals not classified in migraine, tension-type headache, and cluster headache were included in other headache types.
The use of medical care, based on questionnaire response, was categorized as following: frequency of current medical visits (regularly visited, not regularly visited, and not visited); frequency of medical visits in the past 6 months before answering the survey (≥ once/week, once/2 weeks, once/month, once/2 months, once/3 months, <once/3 months); reasons for initially seeing a doctor for headache (top four responses: unable to tolerate headaches, worried about other brain diseases, increased headache frequency, and over-the-counter [OTC] analgesics no longer effective); reasons for seeing a doctor once for headache and not seeing thereafter (top four responses: relieved not to have brain disease that threatened life, too much trouble, no time, and prescription drugs ineffective); and reasons for not seeing a doctor in the past 3 years (top four responses: OTC analgesics effective, used to having a headache, spontaneously resolving after endurance, and pain not sufficiently severe). All responses were provided for the first two questions whereas the top four responses in the migraine group were provided for the last three questions for all headache types.
Clinical features and symptoms, based on questionnaire response, were classified as following: symptoms associated with headache (top nine responses: nausea or vomiting, stiff shoulder, neck pain, photophobia, phonophobia, dizziness, osmophobia, weakness or lethargy, and teary eye on the side of headache); site of pain (unilateral, bilateral, frontal, occipital, periorbital, and other); time of day of headache onset (upon waking, morning, afternoon, evening, other, and no particular time); headache triggers (top 18 responses: fatigue, stress, bad weather such as the time of typhoon, lack of sleep, turning points of the seasons, sunny or rainy days, work or housework, menstruation, excessive sleep, feeling nervous, weekdays, weekends [including holidays], drinking alcohol, release from nervousness, no particular triggers, smell of perfume or cigarettes, and sleep); activities that were interfered by headache (top seven responses: no focus on work or study, unable or unwilling to conduct housework, unwilling to work or study, cancelling plans or appointments, absence from work or school, unable to go outside, and unable to stay in crowded places); and activities that were refrained from or reduced by headache (operating a computer or smartphone, drinking alcohol, going to crowded places, exercising such as playing sports and walking, driving a car, housework [excluding grocery shopping, laundry, and cooking], socializing with friends and playing with children, going to grocery shopping, taking public transportation, cooking, taking a bath, doing laundry, dropping-off and picking-up children or family members, socializing with neighbors, putting on make-up, and other). Time of day of headache onset was stratified by the aforementioned age categories, and activities refrained from or reduced by headache stratified by sex.
Medication use, based on questionnaire responses and medical claims data, was classified as following: medication use in the past 6 months (no prescription drugs, OTC analgesics only, prescription drugs only [acute and prophylactic], and OTC and prescription drugs); number of OTC analgesics types (1 or ≥ 2); and types of prescription drugs for prophylactic treatments (antidepressants, anti-epileptics, calcium channel blockers, angiotensin-receptor blockers/angiotensin converting enzyme inhibitors, beta-blockers, and other) and for acute treatments (acetaminophen, NSAIDs, triptans, ergotamine antiemetic drugs, and other) in the past 6 months.
Severity of pain and activity impairment, based on survey response, was classified as following: severity of pain when not taking or taking medicines (severe = extreme pain or quite a bit of pain, moderate = moderate pain, mild = little pain or no pain); impairment in daily activities (severe = extreme difficulty or severe disruption in daily life, moderate = moderate difficulty in daily life, mild = slightly interferes with daily life or no trouble at all); hoped reduction in headache for improving daily life (slight, almost half, almost none, reduction in pain intensity per attack rather than reduction in pain frequency); migraine-specific quality of life (MS-QOL) scores ; and Work Productivity Activity Impairment (WPAI) scores . MS-QOL was estimated using MSQ version 2.1, which is a 14-item questionnaire measuring the impact of migraine during the past 4 weeks across three domains: role function-restrictive that measures functional limitations on daily, work, and social activities (seven items); role function-preventive that measures functional prevention on daily, work, and social activities (four items); and emotional function that measures the impact on emotion (three items) [16, 17]. The source response data were scaled to range from 0 to 100, with higher score indicating better quality of life . WPAI scores were estimated using the WPAI Questionnaire-General Health for the last 7 days before responding to the survey as follows: 1) percentage of work time missed in the last week due to health conditions (absenteeism); 2) percentage of impairment while working due to health conditions (presenteeism); 3) percentage of overall work impairment due to health conditions; and 4) percentage of activity impairment due to health conditions .