SEATTLE—Recent epidemiologic studies brought to light some significant findings about chronic daily headache. Researchers have learned, for example, that the disorder is nearly twice as common in women as in men. Also, roughly equal proportions of chronic daily headache sufferers have tension-type or migraine headaches, and these individuals have had frequent headaches for seven years, on average. However, “there are people with [chronic daily headache] durations of 30, 40, and 50 years,” said Ann Scher, PhD, at the 44th Annual Scientific Meeting of the American Headache Society.

Only half of those with chronic daily headache seek physician care. Most self-treat with over-the-counter analgesics and about one third meet suggested criteria for analgesic overuse, related Dr. Scher, a postdoctoral fellow in the Laboratory of Epidemiology, Demography, and Biometry at the National Institute on Aging in Bethesda, Maryland.

In three epidemiologic studies, presumably spontaneous remission rates for chronic daily headache ranged from about 30% to 65% during one to four years of follow-up; remission was defined as fewer than 15 headache days per month. However, “true remission, meaning headache less than once a week, was uncommon,” Dr. Scher acknowledged.

DAUNTING DEMOGRAPHICS

Much of the data on chronic daily headache come from six major epidemiologic studies, which were often quite distinct regarding methodology, population demographics, and case definitions. Nevertheless, they all found similar rates of chronic daily headache in the population—around 4%. The disorder is more common in whites than in non-whites, though only somewhat. Onset and remission are usually gradual, but they occur rapidly (in less than a week) in roughly 30% of cases.

While chronic daily headache more often affects women, it has not shown an age effect. “It is possible that the prevalence is, in fact, fairly constant in the elderly and maybe even in childhood,” said Dr. Scher.

An inverse relationship between the disorder and education has appeared in some studies, she noted, and an inconsistent association also has been observed between chronic daily headache and marital status; people who were previously married (divorced, separated, or widowed) had an increased risk in one study but not in another.

MODIFIABLE RISK FACTORS

Several modifiable risk factors for chronic daily headache have been identified. In a two-year case-control study, daily snorers had an odds ratio for headache of 3.3 after adjustment for factors related to sleep-disordered breathing, Dr. Scher reported. Seventeen percent of the risk increase was actually attributable to habitual snoring, she said.

Chronic daily headache onset was also associated with certain potentially stressful life events, such as moving, the death of a family member or close friend, and marital status changes. This association was significant at younger and older ages but tended to be strongest for the over-40 age group.

Caffeine, whether dietary or in medications, was associated with chronic daily headache, too. “But the association was actually limited to the younger cases and was not significant for the older cases,” Dr. Scher remarked. Surprisingly, head injury was not an important risk factor.

VARIABLE PROGNOSIS

Three studies have considered prognostic factors over a one- to four-year follow-up period. The overall chances of true remission (eg, to less than one headache per week) in chronic daily headache are fairly slim, about 15%. Also, based on one study, remission seems to be especially unlikely in elderly cases, even when one uses the more liberal definition (fewer than 15 headache days a month). Indeed, remission rates in those cases tend to fall into the lower end of the reported ranges for that definition.

Other factors associated with a worse prognosis are daily headaches at baseline, later onset and longer duration of headaches, a lower education level, white race, and headache medication overuse. “Of course, high analgesic use could be considered a marker of intractability, not necessarily a risk factor [for a worse prognosis],” suggested Dr. Scher.

Factors unrelated to prognosis are gender, headache type, baseline psychiatric symptoms of depression, head injury, and age over 40. Primary prevention of chronic daily headache should be the ultimate goal of future studies of the disorder, Dr. Scher concluded.

NR

—Timothy Begany

Suggested Reading
Castillo J, Munoz P, Guitera V, Pascual J. Kaplan Award 1998: Epidemiology of chronic daily headache in the general population. Headache. 1999;39:190-196.

Hagen K, Zwart JA, Vatten L, et al. Prevalence of migraine and non-migrainous headache—head-HUNT, a large population-based study. Cephalalgia. 2000;20:900-906.

Lipton RB, Scher AI, Kolodner K, et al. Migraine in the United States: epidemiology and patterns of health care use. Neurology. 2002;58:885-894.

Lu SR, Fuh JL, Chen WT, et al. Chronic daily headache in Taipei, Taiwan: prevalence, follow-up and outcome predictors. Cephalagia. 2001;21:980-986.

Prencipe M, Casini AR, Ferretti C, et al. Prevalence of headache in an elderly population: attack frequency, disability, and use of medication. J Neurol Neurosurg Psychiatry. 2001;70:377-381.

Scher AI, Stewart WF, Liberman J, Lipton RB. Wolff Award 1998. Prevalence of frequent headache in population sample. Headache. 1998;38:497-506.

Wang SJ, Fuh JL, Lu SR, et al. Chronic daily headache in Chinese elderly: prevalence, risk factors, and biannual follow-up. Neurology. 2000;54:314-319.

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