ORIGINAL ARTICLE. Abstract. Introduction

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1 ORIGINAL ARTICLE Prevalence and Characteristics of Headaches in a Socially Active Population Working in the Tokyo Metropolitan Area Surveillance by an Industrial Health Consortium Norihiro Suzuki 1, Yoshiki Ishikawa 2, Shintaro Gomi 3, Nobuhiko Ito 4, Shigeru Watanabe 4, Masako Yokoyama 5, Kazuo Funatsu 5, Hitoshi Miyake 6, Hirokazu Yokoyama 7, Toshihiko Shimizu 1 and Mamoru Shibata 1 Abstract Objective The goal of this study was to determine the prevalence and clinical characteristics of headaches among socially active people working in the Tokyo metropolitan area. Methods We cross-sectionally surveyed 7,917 individuals. The survey assessed demographic characteristics, the prevalence and characteristics of headaches and physician attendance. Results The lifetime prevalence of migraines was 8.9%, while that of tension-type headaches was 14.7%. Women exhibited a higher prevalence of migraines than men (15% vs. 3.7%; p<0.001). The prevalence of migraines and tension-type headaches differed among occupations. Susceptibility to migraines and tensiontype headaches related to working overtime was observed. With respect to the influence of migraines on social activities, 22.4% of the migraineurs had been obliged to miss work due to headaches several times a year. As many as 59.4% of the sufferers had never consulted a physician about their headaches. Moreover, 24.6% of the migraineurs were not in touch with any physician at the time of the survey. The most common reason why they had stopped visiting their physician was that they had been told their headaches were not fatal. Conclusion Migraines adversely affect social activities. These data provide important information for understanding the features of migraines and tension-type headaches in socially active people working in the Tokyo metropolitan area. Key words: migraine, tension-type headache, prevalence, overtime work, doctor attendance (Intern Med 53: , 2014) () Introduction Headaches are the most common neurological symptom in humans, and it has been reported that nearly half of the world s adult population suffers from active headaches. Migraines and tension-type headaches are included as primary headaches in the second edition of the International Classification of Headache Disorders (ICHD-II) (1). Among primary headaches, migraines significantly impact the patient s quality of life (2, 3). It is estimated that nearly 10% of the general population suffers from this potentially disastrous cephalalgic disorder, which mostly affects those between 35 and 45 years of age. The high prevalence of migraines observed during the peak years of employment results in a substantial financial burden on society due to increased Department of Neurology, School of Medicine, Keio University, Japan, Otemachi Medical Center, Mizuho Health Insurance Society, Japan, Health Administration Center, Aoyama Gakuin University, Japan, Tokyo Health Administration Center, Nippon Life Insurance Company, Japan, Mitsukoshi Health and Welfare Foundation Mitsukoshi Clinic, Japan, Fujitsu Limited, Health Promotion Unit, Japan and Health Center, Keio University, Japan Received for publication September 3, 2013; Accepted for publication October 14, 2013 Correspondence to Dr. Toshihiko Shimizu, shimizu-toshi@umin.ac.jp 683

2 medical costs and lost productivity in the United States of America and European countries (4, 5). Therefore, a large number of epidemiological studies of migraines and their economic impact have been published in these countries (6-8). However, in Japan, only a few studies have evaluated the prevalence of primary headaches, such as migraines, in the general population, and fewer still have investigated the prevalence of headaches in the workplace (9, 10). In this study, we determined the prevalence and characteristics of headaches among subjects in the prime of life, defined as socially active individuals, working in the Tokyo metropolitan area. In addition, our study provides important information regarding physician attendance among migraine sufferers in Japan, where triptans have been available for almost ten years. Materials and Methods Between September 2007 and September 2008, we conducted a survey of the prevalence and characteristics of headaches at four institutions located in the Tokyo metropolitan area. These institutions comprised a university hospital, department store, insurance company and computer manufacturing company. A self-administered questionnaire including items assessing demographic characteristics (age, sex and occupation), the incidence of headaches, characteristics of headaches, the frequency of seeking medical attention due to headaches and the relationship between the frequency and severity of headaches and burdens on work within the past 12 months was distributed to all staff at these institutions (Table 1). Questionnaires with missing data for age, sex or occupation were eliminated from the analysis. We diagnosed the type of headache based on the answers provided in the questionnaire. The questionnaire included diagnostic criteria for migraine without aura, such as the frequency, duration and characteristics of headaches, as well as accompanying symptoms, including nausea or photophobia. A migraine was diagnosed if the headache fulfilled these criteria. However, the questionnaire did not include details about aura. Although the questionnaire included questions regarding visual symptoms, such as the occurrence of scintillating scotoma before the headache, it was difficult to diagnose whether the symptoms were truly indicative of focal cerebral dysfunction as defined by the ICHD-II (1). Therefore, in our study, both migraine without aura and migraine with aura were simply classified as migraines. Tension-type headaches were also diagnosed according to the ICHD-II diagnostic criteria. If the headache fulfilled the diagnostic criteria for infrequent episodic, frequent episodic or chronic tension-type headaches, the headache was diagnosed as tension-type headache. Since patients can receive more than one diagnosis in the ICHD-II, respondents with both migraines and tension-type headaches were are included in both the diagnostic group with migraines and the diagnostic group with tension-type headaches. Frequency and contingency tables were used to examine categorical data, which were evaluated with the χ 2 and McNemar tests. A multivariate logistic regression analysis was performed with the prevalence of migraines and tension-type headaches as the dependent variable and occupation, occupational position, sex, age and duration of overtime work as independent variables. Because there were sex differences in the prevalence of migraines and tension-type headaches, we evaluated the independent variables (occupation, occupational position and duration of overtime work) according to sex and thus created new independent variables. Another multivariate logistic regression analysis was performed using the new independent variables, with the prevalence of migraines and tension-type headaches as the dependent variable. The goodness of fit was evaluated according to the Hosmer and Lemeshow test and omnibus tests of model coefficients. Odds ratios (ORs) and their 95% confidence intervals (CIs) are presented. All statistical analyses were performed using the SPSS version 20.0 software package (SPSS Inc.). A value of p<0.01 was considered to be statistically significant. All questionnaire data were obtained after the respondents provided their informed consent, and the study was approved by the Keio University institutional review board (approval ID: ). Results Completed questionnaires were received from 7,917 individuals (4,160 men, 3,675 women, 112 missing sex data); a 77% response rate. Of the responders, 46% were women (Table 2). Lifetime prevalence of migraines and tension-type headaches Among the respondents, the lifetime prevalence of migraines was 8.9% (n=704), while that of tension-type headaches was 14.7% (n=1,167). In terms of sex, the prevalence of migraines was 3.7% (n=154) among 4,159 men and 15% (n=545) among 3,638 women (Table 2). The female/male ratio was 4.1. Women exhibited a higher prevalence of migraines than men (p<0.001, χ 2 test). The highest prevalence of migraines was among subjects between 35 and 39 years of age (19.3%; n=149) in women (n=773) and between those 25 and 29 years of age (7.0%; n=17) in men (n=244). The prevalence of tension-type headaches was 13.2% (n= 552) among men and 16.7% (n=606) among women (Table 2). Women also showed a higher prevalence of tensiontype headaches than men (p<0.001, χ 2 test). Association between the prevalence of headaches and occupation The OR of migraines for women in clerical, sales, system engineering, nursing and other occupations was 3.90 (95% CI= ), 4.64 (95% CI= ), (95% CI= ), 3.68 (95% CI= ) and 4.06 (95% CI= 684

3 Table 1. A Self-administered Questionnaire 685

4 Table 2. Lifetime Prevalence of Migraines and Tension-type Headaches by Sex and Age Group Sex Age Total Migraine Tension-type headache Sample Men (0%) 0 (0%) (1.0%) 11 (10.5%) (7%) 33 (13.5%) (4.7%) 78 (18.5%) (6.0%) 95 (17.4%) (5.6%) 130 (20.9%) (3.9%) 84 (18.1%) (2.1%) 65 (8.7%) (1.3%) 39 (5.8%) (1.5%) 17 (5.1%) Total 4, (3.7%) 552 (13.2%) Women 6 1 (16.7%) 0 (0%) (11.8%) 37 (16.8%) (13.4%) 79 (20.3%) (12.6%) 94 (18.0%) (19.3%) 135 (17.5%) (18.8%) 113 (20.1%) (18.3%) 78 (17.6%) (11.9%) 41 (12.5%) (7.4%) 22 (7.8%) (3.5%) 7 (6.2%) Total 3, (15.0%) 606 (16.7%) Unstated (4.2%) 9 (7.5%) Total 7, (8.9%) 1,167 (14.7%) Table 3. Association between the Prevalence of Migraines and Occupation Sex and Migraine (n = 693) Type of Odds ratio (95% CI) p Occupation Men: Clerical 1 (reference) Men: Sales 1.47 ( ) 0.22 Men: R & D 1.87 ( ) 0.08 Men: SEs 1.01 ( ) 0.97 Men: Physicians 0.44 ( ) 0.20 Men: Lab. Assistants 2.64 ( ) 0.29 Men: Others 0.88 ( ) 0.73 Women: Clerical 3.90 ( ) Women: Sales 4.64 ( ) Women: SEs ( ) Women: Physicians 2.97 ( ) 0.02 Women: Nurses 3.68 ( ) Women: Pharmacists 7.93 ( ) 0.02 Women: Lab. Assistants 2.74 ( ) 0.03 Women: Others 4.06 ( ) R & D: Research and Development SEs: System engineers Table 4. Association between the Prevalence of Tension-type Headaches and Occupation Sex and Tension-type headache (n = 1,138) Type of Odds ratio (95% CI) p Occupation Men: Clerical 4.06 ( ) Men: Sales 2.76 ( ) Men: R & D 2.17 ( ) 0.03 Men: SEs 4.00 ( ) Men: Physicians 9.22 ( ) Men: Lab. Assistants 1.53 ( ) 0.64 Men: Others 4.61 ( ) Women: Clerical 1.04 ( ) 0.87 Women: Sales 0.87 ( ) 0.64 Women: SEs 0.37 ( ) 0.11 Women: Physicians 1.36 ( ) 0.52 Women: Nurses 1.10 ( ) 0.75 Women: Pharmacists 0.51 ( ) 0.45 Women: Lab. Assistants 1.48 ( ) 0.42 Women: others 1 (reference) R & D: Research and Development SEs: System engineers ), respectively, compared with men employed as clerical personnel (Table 3). In terms of tension-type headaches, the OR for men employed as clerical personnel, sales personnel, system engineers, physicians and others was 4.06 (95% CI= ), 2.76 (95% CI= ), 4.00 (95% CI= ), 9.22 (95% CI= ) and 4.61 (95% CI= ), respectively, compared with women in the other occupations category (Table 4). Duration of overtime work We analyzed the association between the incidence of headaches and the duration of overtime work. As shown in Table 5, the OR of migraines for men worked <45 h/month of overtime and those who worked 45 h/month of overtime was 0.34 (95% CI= ) and 0.35 (95% CI= ), respectively, compared with women who worked 45 h/ 686

5 Table 5. Association between the Incidence of Headaches and the Duration of Overtime Work Sex and Migraine (n = 693) Tension-type headache (n = 1,138) the duration of Odds ratio (95% CI) p Odds ratio (95% CI) p overtime work Men: <45 h/month 0.34 ( ) ( ) Men: 45 h/month 0.35 ( ) ( ) Women: <45 h/month 1.35 ( ) ( ) 0.28 Women: 45 h/month 1 (reference) 1 (reference) Men: <45 h/month 1 (reference) 1 (reference) Men: 45 h/month 1.03 ( ) ( ) 0.87 Women: <45 h/month 3.92 ( ) ( ) Women: 45 h/month 2.90 ( ) ( ) month. Among women, the OR of migraines for those who worked <45 h/month and those who worked 45 h/month was 3.92 (95% CI= ) and 2.90 (95% CI= ), respectively, compared with men who worked <45 h/month. In terms of tension-type headaches, the OR for men who worked <45 h/month and those who worked 45 h/month was 2.90 (95% CI= ) and 2.79 (95% CI= ), respectively, compared with women who worked 45 h/ month. Among women, the OR of tension-type headaches for those who worked <45 h/month and those who worked 45 h/month was 0.25 (95% CI= ) and 0.34 (95% CI= ), respectively, compared with men who worked <45 h/month. Influence on social activities The influence of migraine on social activities was remarkable, as witnessed by the fact that 25.1% of the migraineurs (n=704) had been obliged to miss work due to headaches several times during the course of a single year. In fact, 2.7% of the 704 migraineurs were unable to work once a month. In comparison, tension-type headache sufferers (n= 1,167) were less frequently affected in terms of restrictions on their social activities; 89.9% reported no impact of headaches on their work. Therefore, our results indicate that the effects of migraines on social activities are greater than those of tension-type headaches (p<0.001, χ 2 test). Physician attendance and medication use Among the migraineurs (n=704), only 1.3% regularly visited their physicians, and 59.4% had never consulted with a physician about their headaches. A total of 24.6% were not in touch with any physician at the time of the survey and 12.5% visited their physician on an as-needed basis. Among the tension-type headache sufferers (n= 1,167), 79.7% had never visited a physician about their headaches, 12.5% had visited a physician only in the past, 6.2% visited a physician on an as-needed basis and 0.5% reported visiting a physician regularly. Although both the migraine and tension-type headache sufferers exhibited a low rate of physician attendance, the percentage of respondents visiting a physician was significantly higher among the migraineurs than among the tension-type headache sufferers (p<0.001, χ 2 test). The most common reason why respondents stopped visiting their physician (n=173 in migraineurs who had visited a physician; n=146 in tension-type headache sufferers who had visited a physician) was that they had been told that their headaches were not fatal (45.1% of migraineurs and 45.9% of tension-type headache sufferers). The rate of this response was significantly higher than that of the other reasons (p<0.0001, McNemar test). The second most common reason was that the respondents had been unable to obtain adequate advice about their headaches from their physician (20.2% of migraineurs and 10.3% of tension-type headache sufferers). Other reasons included that there was no time to see a physician (14.5% of migraineurs and 8.9% of tension-type headache sufferers) and that no headache medications were given on past visits to a physician (2.9% of migraineurs and 0.7% of tension-type headache suffers). In regard to how the headache sufferers dealt with their headaches, the respondent reported that they tended to use drugs obtained from pharmacies (60.8% of the 704 migraineurs and 48.1% of the 1,167 tension-type headache sufferers, both proportions were significantly higher than that for other headache types; p<0.0001, McNemar test). The second most common measure for dealing with headaches was physical therapy (46.0% of migraineurs and 32.6% of tension-type headache sufferers). Only 23.2% of the migraineurs and 15.9% of the tension-type headache sufferers reported using drugs prescribed at medical institutions. Doing nothing in particular to relieve their headaches was reported by 2.4% of the migraineurs and 15.1% of the tension-type headache sufferers. Discussion Our study revealed the prevalence of migraines and tension-type headaches among workers in the metropolitan area around Tokyo. A previous nationwide survey in Japan demonstrated that the overall prevalence of migraines was 8.4%, while that of tension-type headaches was 22.4% (9). Another population-based survey in Japan revealed that the one-year prevalence of migraines and tension-type headaches was 6.0% and 21.7%, respectively (10). Our data are consistent with previously reported incidences of migraines 687

6 and tension-type headaches; therefore, it is inferred that our questionnaire is appropriate for screening primary headaches, although it did not completely eliminate the detection of secondary headaches. Since the lifetime prevalence of headaches is known to exhibit a cumulative trend, the incidence of headaches is expected to reach a saturated level in midlife and maintain a steady-state level thereafter. However, our data indicated that the lifetime prevalence of migraines and tension-type headaches tended to be lower at older ages. Similar observations have been reported in other surveys (11-14). According to these studies, this discrepancy can be explained by recall bias, which refers to the tendency to report the most recent experience with headaches, as well as cohort effects and mortality bias. Therefore, these factors may have also affected the lifetime prevalence of migraines and tension-type headaches in this study. The present study also examined the association between the prevalence of headaches and occupation. Although many clinicians have the impression that there is an association between the prevalence of headaches and occupation, there have thus far been no published epidemiological data showing such an association. Therefore, in this study, we demonstrated differences in the prevalence of headaches among various types of jobs for the first time. Since several epidemiological studies have raised the possibility that long work hours constitute a risk factor of cerebro- and cardiovascular diseases, we evaluated the association between the prevalence of migraines or tension-type headaches and overtime work (15, 16). In Japan, employers make efforts to reduce the number of overtime work hours in order to improve accumulated fatigue due to excessive work. As a consequence, the Ministry of Health, Labour and Welfare of Japan revised the Labour Standards Act, and Japanese employers are now required to limit the number of overtime hours an employee can work to 45 hours per month (Ministry of Health, Labour and Welfare of Japan. Revised Labour Standards Act. english/policy/affairs/dl/07.pdf., 5 October 2013, date last accessed). Therefore, we used 45 hours per month as a cutoff value to assess the impact of overtime. However, our data did not show a robust increase in the prevalence of headaches in the subjects who worked more than 45 hours per month of overtime work. These findings suggest that it is important to set the cut-off value to less than 45 hours per month of overtime in order to reduce the impact of headaches induced by overtime work. The present study found that approximately 60% of migraine patients had never consulted a physician, despite experiencing a remarkable influence of headaches on their social life. Migraines are known to cause severe disability in their social activities. However, only a fraction of headache patients seek medical assistance from a doctor (17). Some studies have indicated the possibility that the low rate of physician attendance results in the reliance of a large number of migraineurs on over-the-counter medications to treat their headaches (18, 19). In fact, our data also indicated that approximately 60% of migraineurs use over-the-counter analgesics (20, 21). This is likely to put migraine sufferers at a greater risk of developing medication-overuse headaches. Several studies have attempted to address this issue by exploring reasons why migraine and tension-type headache patients do not seek medical attention (22, 23). In addition to these studies, Kotani et al. conducted a survey of this issue in Japanese migraine and tension-type headache patients (24). According to these reports, reasons for not seeking medical attention include an insufficient severity of headaches and/or the amenability of the headaches to overthe-counter medications. An important finding of this study is the identification of reasons why migraine and tensiontype headache patients in Japan do not consult physicians. Although the response that the subjects did not obtain adequate advice about their headaches from their physician was a similar reason to that observed in the results of a Canadian Population Survey, the answers that the headaches were not fatal and there was no time to see a physician were not included in the results of that survey. These findings provide important clues to preventing Japanese headache patients from not consulting a physician. However, our population-based study has potential limitations related to recall and selection bias. Recall bias may be present because the recall of events occurring almost a decade in the past is likely to be imperfect. In addition, selection bias may have affected our results because we included only four institutions in this study. Despite these caveats, our data provide intriguing information in terms of the prevalence of primary headaches among socially active people working in the Tokyo metropolitan area. Furthermore, our study highlights the potential importance of providing lectures by headache specialists for office workers who suffer from headaches. Author s disclosure of potential Conflicts of Interest (COI). Nobuhiko Ito: Employment, Nippon Life Insurance. Shigeru Watanabe: Employment, Nippon Life Insurance. Hitoshi Miyake: Employment, Fujitsu. Acknowledgement The authors express our gratitude to Professor Kazuyuki Omae (Department of Preventive Medicine and Public Health, School of Medicine, Keio University) for his insightful comments on the statistical analysis in this article. This research received no specific grants from any funding agency in the public, commercial or not-for-profit sectors. References 1. Headache Classification Subcommittee of the International Headache Society. The international classification of headache disorders, 2nd edition. Cephalalgia 24 (Suppl. 1): 9-160, Freitag FG. The cycle of migraine: patients quality of life during and between migraine attacks. Clin Ther 29: , Turner-Bowker DM, Bayliss MS, Ware JE Jr, Kosinski M. Usefulness of the SF-8 Health Survey for comparing the impact of migraine and other conditions. Qual Life Res 12: ,

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