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Various forms of headache, properly called headache disorders, are among the most common disorders of the nervous system. They are pandemic and, in many cases, life-long conditions.
Headache itself is a painful and often disabling feature of a relatively small number of primary headache disorders. It also occurs secondarily to a considerable number of other conditions. A wide range of headache types have been classified in detail by the International Headache Society (table I). The most common among them � tension-type headache (TTH), migraine, cluster headache and the so-called chronic daily headache syndromes � cause substantial levels of disability. Headache has been and continues to be underestimated in scope and scale, and headache disorders remain under-recognized and under-treated throughout the world.
A worldwide problem
Although the epidemiology of headache disorders is only partly documented, taken together, headache disorders are extraordinarily common. Population-based studies have mostly focused on migraine which, although the most frequently studied, is not the most common headache disorder. Other types of headache, such as the more prevalent TTH and sub-types of the more disabling chronic daily headache, have received less attention. Few population-based studies exist for developing countries where limited funding and large and often rural populations, coupled with the low profile of headache disorders compared with other diseases, prevent the systematic collection of information.
In developed countries, Tension Type Headache (TTH) alone affects two-thirds of adult males and over 80% of females. Extrapolation from figures for migraine prevalence and attack incidence suggests that 3000 migraine attacks occur every day for each million of the general population. Less well recognized is the toll of chronic daily headache: up to one adult in 20 has headache every or nearly every day.
Not only is headache painful, but headache disorders are also disabling. Worldwide, according to the World Health Organization (WHO), migraine alone is 19th among all causes of years lived with disability (YLDs). Headache disorders impose recognizable burden on sufferers including sometimes substantial personal suffering, impaired quality of life and financial cost. Repeated headache attacks, and often the constant fear of the next one, damage family life, social life and employment. For example, social activity and work capacity are reduced in almost all migraine sufferers and in 60% of TTH sufferers.
The long-term effort of coping with a chronic headache disorder may also predispose the individual to other illnesses. For example, depression is three times more common in people with migraine or severe headaches than in healthy individuals.
Migraine is a primary headache disorder with, almost certainly, a genetic basis. Activation of a mechanism deep in the brain causes release of pain-producing inflammatory substances around the nerves and blood vessels of the head. Why this happens periodically, and what brings the process to an end in spontaneous resolution of attacks, are to a large extent uncertain. Adults with migraine describe episodic attacks with specific features (see table below), of which nausea is the most characteristic. Attack frequency is anywhere between once a year and once a week (most commonly once a month). In children, attacks tend to be of shorter duration and abdominal symptoms more prominent.
Commonly starting at puberty, migraine most affects those aged between 35 and 45 years but can trouble much younger people, including children. European and American studies have shown that 6-8% of men and 15-18% of women experience migraine each year. A similar pattern is seen in Central and South America. Researchers in Puerto Rico, for example, have found 6% of men and 17% of women suffering from migraine. A survey conducted in Turkey revealed even greater prevalence in that country: 10% in men and 22% in women. The higher rates in women everywhere (2-3 times those in men) are hormonally-driven.
Migraine appears somewhat less prevalent, but still common, in Asia (3% of men and 10% of women) and in Africa (3-7% in community-based studies). Major studies have yet to be conducted. But for example in India, anecdotal evidence suggests similar levels. �High temperatures and light levels for more than eight months of the year, the heavy noise pollution, the Indian habit of not having breakfast, frequent fasting and eating rich, spicy and fermented food, are common triggers,� says Dr K. Ravishankar from Mumbai, a leading specialist.
Tension-type headache (TTH)
The mechanism of TTH is poorly understood, although it has long been regarded as a headache with muscular origins. It may be stress-related or associated with musculoskeletal problems in the neck. TTH has distinct sub-types. As experienced by very large numbers of people, episodic TTH occurs, like migraine, in attack-like episodes. These usually last no more than a few hours, but can persist for several days. Chronic TTH, one of the chronic daily headache syndromes, is less common than episodic TTH but present most of the time: it can be unremitting over long periods. This variant of TTH is much more disabling. Headache in either case is usually mild or moderate and generalized, though it can be one-sided. It is described as pressure or tightness, like a band around the head, sometimes spreading into or from the neck. It lacks the specific features and associated symptoms of migraine.
TTH often begins during the teenage years, affecting three women to every two men, and reaches peak levels in the 30s. Episodic TTH is the most common headache disorder, reported by over 70% of some populations. Its prevalence varies greatly. African community-based studies, for example, have found only 1.7% of the population affected, but cultural attitudes to reporting a relatively minor complaint may largely explain this finding. Chronic TTH affects 1-3% of adults.
Cluster headache (CH)
CH is one of a group of primary headache disorders (trigeminal autonomic cephalalgias) of uncertain mechanism that are characterized by frequently recurring, short-lasting but extremely severe headache. CH also has episodic and chronic forms. Episodic CH occurs in bouts (clusters), typically of 6-12 weeks� duration once a year or two years and at the same time of year. Strictly one-sided intense pain develops around the eye once or more daily, mostly at night, until the pain diminishes after 30-60 minutes. The eye is red and waters, the nose runs or is blocked on the affected side and the eyelid may droop. In the less common chronic CH there are no remissions between clusters. The episodic form can become chronic, and vice versa, but once CH has struck it may recur over 30 years or more.
Though relatively uncommon (affecting fewer than 1 in 1000 adults), CH is clearly highly recognizable. It is unusual among primary headache disorders in affecting six men to each woman. Most people developing CH are in their 20s or older.
Medication-overuse headache (MOH)
Chronic and excessive use of medication to treat headache is the cause of MOH, another of the chronic daily headache syndromes. A typical history of MOH begins with episodic headache � migraine or TTH. The condition is treated with an analgesic or other medication. Over time, headache episodes become more frequent, as does medication intake, until both are daily. A common and probably key factor in the development of MOH is a switch to pre-emptive use of medication. MOH is oppressive, persistent and often at its worst on awakening. What constitutes overuse is not clear. Suggested limits are the regular intake of simple analgesics on 15 or more days per month or of codeine- or barbiturate-containing combination analgesics, ergotamine or triptans on more than 10 days a month. In prevalence, MOH far outweighs all other secondary headaches. It affects up to 5% of some populations, women more than men.
Headache disorders and public health
While those suffering from headache disorders bear much of the burden, they do not carry it all. Because headache disorders are most troublesome in the productive years (late teens to 50s), estimates of their financial cost to society � principally from lost working hours and reduced productivity � are massive. In the United Kingdom, for example, some 25 million working- or school-days are lost every year because of migraine alone. TTH, less disabling but more common, and chronic daily headache, less common but more disabling, together cause losses which are almost certainly of at least similar magnitude. Headache rarely signals serious underlying illness; its public-health importance lies in its causal association with these personal and societal burdens of pain, disability, damaged quality of life and financial cost. Headache is high among causes of consulting medical practitioners. A survey of neurologists found that up to one-third of all their patients consulted because of headache � more than for any other complaint.
Headache ought to be a public-health concern. Yet there is good evidence that very large numbers of people troubled by headache do not receive effective care. For example, in representative samples of the general populations of the United States of America and the United Kingdom, only half of those identified with migraine had seen a doctor for headache-related reasons in the previous 12 months, and only two-thirds had been correctly diagnosed. Most were solely reliant on over-the-counter medications.
Barriers to effective care
The common headache disorders require no special investigation and they are diagnosed and managed with skills that should be generally available to physicians. In theory, therefore, most headache can be optimally managed in primary care. The barriers vary throughout the world, but may be classified as clinical, social or political/economic.
Lack of knowledge among health-care providers is the principal clinical barrier. This problem begins in medical schools where there is limited teaching on the subject, the consequence of low priority accorded to it. It is likely to be even more pronounced in countries with fewer resources generally and, as a result, more limited access to doctors and effective treatments.
Poor awareness extends to the general public. Headache disorders are not perceived by the public as serious since they are mostly episodic, do not cause death and are not contagious. In fact, headaches are often trivialized. These important social barriers inhibit people who might otherwise seek help from doctors. Surprisingly poor awareness exists even among people directly affected A Japanese study found, for example, that many patients were unaware that their headaches were migraine, or that this required proper medical care. The low consultation rates in developed countries may indicate that many sufferers are unaware that effective treatments exist.
Many governments, seeking to constrain health-care costs, do not acknowledge the substantial burden of headache on society. They might not recognize that the direct costs of treating headache are small in comparison with the huge indirect-cost savings that might be made (eg, by reducing lost working days) if resources were allocated to treat headache disorders appropriately.
Management and prevention of headache disorders
The great majority of headache disorders can be successfully managed. However:
The key in most areas of the world is education, which first should create awareness that headache disorders are a medical problem requiring treatment. Education of health-care providers should encompass correct recognition, diagnosis and treatment of common headache disorders.
What needs to be done?
The evident burden of headache disorders on individuals and on society is sufficient to justify a strategic change in the approach to headache management. In order to implement beneficial change, the following must be achieved globally:
These steps form the framework of the Global Campaign to Reduce the Burden of Headache World-wide, a joint action between WHO and the World Headache Alliance, International Headache Society and European Headache Federation.
Sources: US Department of Health; The World Health Organization