Chronic daily headache relates to the daily or almost-daily occurrence of headache for a prolonged period of time. However, not all daily or almost-daily headaches fall under this denominator, as is the case with the daily or almost-daily headaches of (chronic) cluster headache and (chronic) paroxysmal hemicrania. These conditions can be referred to as paroxysmal daily headaches in which the headaches occur in well-defined attack patterns. In cluster headache, the attack pattern is that of headaches occurring once or twice a day and lasting 1 to 2 hours, whereas in paroxysmal hemicrania, it is that of headaches occurring 5 to 15 times per day and lasting 10 to 30 minutes.

Of the nonparoxysmal daily headaches, hemicrania continua is a condition that does not fall under the denominator of chronic daily headache, either. However, it is discussed in this chapter because it is very difficult, if not impossible, to distinguish from chronic daily headache on the basis of presentation alone. It differs from chronic daily headache in having a somewhat more consistent and less variable intensity of the pain and in an absolute response to preventive treatment with indomethacin.

In The International Classification of Headache Disorders, 2nd edition,¹ hemicrania continua is described under 4.7 as a persistent, strictly unilateral headache responsive to indomethacin. The diagnostic criteria are:

1. 
   

   Headache for more than 3 months fulfilling criteria B through D.

   
   
2. 
   

   All of the following characteristics:

   
   
   
   
   1. 
      

      Unilateral pain without side-shift.

      
      
   2. 
      

      Daily and continuous, without pain-free periods.

      
      
   3. 
      

      Moderate intensity but with exacerbations of severe pain.

   
   
3. 
   

   At least one of the following autonomic features occurs during exacerbations and ipsilateral to the side of pain:

   
   
   
   
   1. 
      

      Conjunctival injection and/or lacrimation.

      
      
   2. 
      

      Nasal congestion and/or rhinorrhea.

      
      
   3. 
      

      Ptosis and/or miosis.

   
   
4. 
   

   Complete response to therapeutic doses of indomethacin.

   
   
5. 
   

   Not attributed to another disorder.

In terms of the diagnoses listed in The International Classification of Headache Disorders, chronic daily headache comprises the following three: chronic migraine (1.5.1), chronic tension-type headache (2.3), and new daily-persistent headache (4.8).

Chronic migraine is described as migraine headache occurring on 15 or more days per month for more than 3 months in the absence of medication overuse. The diagnostic criteria are:

1. 
   

   Headache fulfilling criteria C and D for 1.1 Migraine without aura on 15 or more days per month for more than 3 months.

   
   
2. 
   

   Not attributed to another disorder.

The criteria C and D for 1.1 Migraine without aura are as follows:

3. 
   

   Headache has at least two of the following characteristics:

   
   
   
   
   1. 
      

      Unilateral location.

      
      
   2. 
      

      Pulsating quality.

      
      
   3. 
      

      Moderate or severe pain intensity.

      
      
   4. 
      

      Aggravation by or causing avoidance of routine physical activity.

   
   
4. 
   

   During the headache, at least one of the following:

   
   
   
   
   1. 
      

      Nausea and/or vomiting.

      
      
   2. 
      

      Photophobia and phonophobia.

In 2006, the Headache Classification Subcommittee² changed the diagnostic criteria for chronic migraine as follows to be more inclusive:

1. 
   

   Headache on 15 days or more per month for more than 3 months.

   
   
2. 
   

   Occurring in a patient who has had at least five attacks fulfilling criteria for 1.1 Migraine without aura.

   
   
3. 
   

   On 8 or more days per month for more than 3 months, headache has fulfilled C1 and/or C2 below, that is, it has fulfilled criteria for pain and associated symptoms of 1.1 Migraine without aura

   
   
   
   
   1. 
      

      Has at least two of a through d:

      
      
      
      
      1. 
         

         Unilateral location.

         
         
      2. 
         

         Pulsating quality.

         
         
      3. 
         

         Moderate or severe intensityc.

         
         
      4. 
         

         Aggravation by or causing avoidance of routine physical activity and has at least one of a or b.

         
         
      5. 
         

         Nausea and/or vomiting.

         
         
      6. 
         

         Photophobia and phonophobia.

      
      
   2. 
      

      Treated and relieved by triptan(s) or ergot before the expected development of C1 above.

   
   
4. 
   

   No medication overuse and not attributed to another causative disorder.

Chronic tension-type headache is described as a disorder evolving from episodic tension-type headache, with daily or very frequent episodes of headache lasting minutes to days. The diagnostic criteria are:

1. 
   

   Headache occurring on 15 or more days per month on average for more than 3 months (180 or more days per year) and fulfilling criteria B through D.

   
   
2. 
   

   Headache lasts hours or may be continuous.

   
   
3. 
   

   Headache has at least two of the following characteristics:

   
   
   
   
   1. 
      

      Bilateral location.

      
      
   2. 
      

      Pressing/tightening (nonpulsating) quality.

      
      
   3. 
      

      Mild or moderate intensity.

      
      
   4. 
      

      Not aggravated by routine physical activity such as walking or climbing stairs.

   
   
4. 
   

   Both of the following:

   
   
   
   
   1. 
      

      No more than one of photophobia, phonophobia, or mild nausea.

      
      
   2. 
      

      Neither moderate or severe nausea nor vomiting.

   
   
5. 
   

   Not attributed to another disorder.

New daily-persistent headache is described as headache that is daily and unremitting from very soon after onset (within 3 days at most). The diagnostic criteria are:

1. 
   

   Headache for more than 3 months fulfilling criteria B through D.

   
   
2. 
   

   Headache is daily and unremitting from onset of within 3 days from onset.

   
   
3. 
   

   At least two of the following pain characteristics:

   
   
   
   
   1. 
      

      Bilateral location.

      
      
   2. 
      

      Pressing/tightening (nonpulsating) quality.

      
      
   3. 
      

      Mild or moderate intensity.

      
      
   4. 
      

      Not aggravated by routine physical activity such as walking or climbing stairs.

   
   
4. 
   

   Both of the following:

   
   
   
   
   1. 
      

      No more than one of photophobia, phonophobia, or mild nausea.

      
      
   2. 
      

      Neither moderate or severe nausea nor vomiting.

   
   
5. 
   

   Not attributed to another disorder.

Regarding the preceding diagnostic criteria, of the four nonparoxysmal, daily-headache conditions, two remarks should be made: (1) The diagnosis of the condition Sjaastad and I³ described as hemicrania continua does not require “exacerbations of severe pain” or “autonomic features.” (2) The criteria under C and D for the diagnosis of chronic tension-type headache are the same as those under C and D for that of new daily-persistent headache. This suggests that abrupt, as opposed to gradual, onset of daily or almost daily headache is unique to chronic tension-type headache; in my experience, it is not and is also quite common in chronic migraine. In addition, chronic migraine can also develop out of a history of episodic tension-type headache.

With regard to the prevalence of daily headache in the general population, the most reliable information comes from a non-headache study conducted in the Netherlands in 1975–1976.⁴ The study was conducted in two districts of Zoetermeer, a midsize town near Leiden, and involved a random sample of 15,563 subjects. The sample size was 4522 (29% of the population), and the response rate was 77%, generating 2198 subjects who were 20 years of age or older. The respondents were asked to fill out a questionnaire that included the following question: “How often do you have headache?” One of the answer options was “daily.” In the study, 6% of the respondents aged 20 years or older (4% of the men, 8% of the women) acknowledged the daily occurrence of headache. The highest prevalence was found in the age groups 20 to 24 years (8%) and older than 64 years (8%), and the lowest prevalence in the age group 35 to 54 years (5%).

The prevalence of frequent headache, that is, headaches occurring at least 180 days per year, in the general population is known from two more recent studies.^5,6 One of the studies was conducted in Baltimore County, Maryland. It involved 13,343 randomly selected subjects 18 to 65 years of age, comprising 77% of the total of 17,237 eligible subjects. Of the respondents, 40% were men and 60% were women, and their median age was 38 years. The 1-year prevalence of frequent headache was 4%: 3% in men and 5% in women. Using the International Headache Society (IHS) criteria for chronic tension-type headache and Silberstein’s modified criteria for transformed migraine,⁷ the investigators found a prevalence of 2.2% for chronic tension-type headache, 1.3% for frequent headache with migrainous features, and 0.6% for other frequent headaches. They found the prevalence of frequent headache to be highest in the age group 41 to 55 years and lowest in the age group 56 to 65 years.

The other study was conducted in Camargo, Spain. The study involved 1883 subjects older than 14 years of age, which was 84% of the randomly selected sample of 2252. Of the respondents, 47% were men and 53% were women. Participants who indicated that they had headaches 10 days per month or more were requested to keep a headache diary for 1 month. On the basis of the diary, the prevalence of frequent headache—that is, headaches occurring 15 days per month or more—was determined to be 4.7%: 1.0% in men and 8.7% in women. The mean age of the subjects with frequent headache was 50 years; the mean age at onset of the frequent headaches was 38 years. Using the criteria presented earlier, the prevalence of chronic tension-type headache was determined to be 2.2% and that of transformed migraine 2.4%. Overuse of abortive medications was found to be the case in (only) 19% of the patients with chronic tension-type headache and in 31% of those with transformed migraine.

With regard to frequent headache, Langemark and colleagues⁸ studied the clinical features of 148 patients with chronic tension headache. The patients had to have at least 10 days with headache per month and no more than one migraine attack. Ninety-three percent of them turned out to have at least 28 days with headache per month, that is, daily headaches (Fig. 32-1). With regard to headache dynamics, this suggests that once headaches have increased to a frequency of 2 or 3 days per week, they rapidly progress to daily or almost-daily occurrence. The implication of this observation for the diagnostic criteria of chronic daily headache is that there is no need for an arbitrary number such as 15 (or 180). The diagnostic criterion for the condition with regard to frequency of headache could simply be “daily or near/almost daily,” and the same simplification could be made for chronic tension-type headache. Everything that falls short of this frequency criterion would be episodic, that is, episodic tension-type headache or (episodic) migraine. This observation also means that the prevalence of frequent headache can be equated with that of daily headache.

On the basis of the preceding epidemiologic studies, and taking the study by Langemark and colleagues into account, it can safely be stated that the prevalence of daily headache in the general population is approximately 5%. About half of these headaches are accounted for by chronic tension-type headache. With regard to age and gender characteristics of chronic daily headache, women are affected two times more often than are men, but age does not seem to have much of an effect on the prevalence of the condition.

The prevalence of chronic tension-type headache in the general population was also separately determined in Denmark.⁹ The study included 740 (76%) of 975 randomly selected subjects out of a total population of 325,621. The subjects were interviewed clinically, generating a prevalence number for chronic tension-type headache of 3%: 2% in men and 5% in women. It can, therefore, be safely stated that the prevalence of chronic tension-type headache in the general population is 2% to 3%, which accounts for about half of daily headaches.

In a study of chronic daily headache that my colleagues and I conducted,^10–12 we defined the condition as headaches occurring at least 5 days per week for a period of 1 year or longer. We excluded only the patients with paroxysmal daily headaches—that is, cluster headache and paroxysmal hemicrania—in order to capture as much of the presentation, development, and outcome of chronic daily headache as possible. The study was conducted in 258 patients from my private headache practice, 19% men and 81% women, with an average age at consultation of 42 years. The distribution of the age of (any) headache onset for the men and women separately is shown in Figure 32-2. Seventy-seven percent of the patients (69% of the men and 79% of the women) experienced the onset of headache before the age of 30 years. The onset of headache occurred in the second decade of life in 36% of the women, compared with 24% of the men. The peak of headache onset in the second decade in women is consistent with the importance of the menstrual cycle in headache occurrence.

With regard to diurnal pattern, the daily headaches were present on awakening or occurred in the course of the morning in 79% of the patients, occurred in the afternoon or evening in 6%, and had a variable time of onset in 15% (Fig. 32-3). In 25% of patients, the headaches were worst on awakening or in the course of the morning; in 53%, they were worst in the afternoon or evening, and in 22%, they were worst at a variable time of the day. The results agree with my clinical observation that daily headaches come in two distinct diurnal patterns. In the most common pattern, the headaches gradually increase in intensity as the day progresses, being worst in the afternoon or evening. According to the results of the study, this is the pattern in more than half of the patients with chronic daily headache. In the less common pattern, which I have referred to as the reversed diurnal pattern, the headaches are worst on awakening in the morning and gradually improve as the day progresses. This was the case in one-quarter of the patients, while in the remaining one-quarter, the diurnal course of the headaches was variable.