Headache is a common pain symptom that inflicts a substantial burden on individuals and on society. Headache has many causes; a range of headache diagnoses was defined for the first time by the International Headache Society (IHS) in 1988 in the first edition of the International Classification of Headache Disorders (ICHD-1).1 The second edition of the International Classification of Headache Disorders (ICHD-2) was published by the IHS in 2004, and the third edition (ICHD-3 beta version) was published in 2013.2,3 The ICHD-3 beta version classifies headache disorders into three major categories: (1) primary headaches; (2) secondary headaches; and (3) painful cranial neuropathies, other facial pains, and other headaches. Secondary headache disorders result from an underlying condition, such as a sinus infection or brain tumor. In primary headache disorders, the headache disorder is the fundamental problem. The primary headaches include four categories: migraine, tension-type headache (TTH), trigeminal autonomic cephalalgias (TACs), and other primary headache disorders. The two most common types of primary headache disorders are episodic tension-type headache (ETTH) and migraine.
The epidemiology of headache varies by headache type and demographics. ETTH, the most common headache type, affects slightly more women than men.4–9 Between the ages of 18 and 65 years, about 36% of men and 42% of women have ETTH.10 In contrast, migraine occurs approximately three times more often in women than in men: approximately 18% of women and 6% of men between 12 and 80 years of age have migraine.11,12
Episodic tension-type headache exerts a modest impact on the individual; however, the aggregate societal impact is high because the disorder is so prevalent. Although migraine is less common, individual attacks are considerably more painful and disabling and often result in lost work time. Because the societal impact of both ETTH and migraine is significant, this chapter focuses on the epidemiology of the two disorders. This chapter does not cover secondary headaches because the epidemiology of the underlying condition is an important determinant of the epidemiology of the related headaches. This chapter begins with a review of the diagnostic criteria for migraine and TTH followed by a review of migraine epidemiology, including incidence, prevalence, and public health impact. The chapter closes with a review of the epidemiology of TTH.
Migraine is characterized by various combinations of neurologic, gastrointestinal, and autonomic changes that occur during different phases of the migraine attack. Although the ICHD-3 beta version defines five major categories of migraine, by far the two most important are migraine without aura (1.1) and migraine with aura (1.2). The ICHD-3 beta version definitions for migraine with and without aura are found in Tables 27-1 and 27-2. The revised diagnostic criteria for 1.3, chronic migraine, as published by the IHS in the ICHD-3 beta version, are found in Table 27-3.