Frequency of headache is related to sensitization: a population study

Central sensitization is thought to play an important role in the chronification of tension-type headache and in the maintenance and exacerbation of the migraine attack. It has, however, almost exclusively been studied in highly selected patients from headache clinics. The aim of the present study was to evaluate pain perception in primary headaches in the general population. Stimulus-response functions for pressure versus pain, tenderness and pressure pain thresholds were studied in a random sample of 523 adults from the general population. All results were controlled for the effects of age and gender. The area under the stimulus-response function was increased in chronic- and frequent episodic tension-type headache compared with subjects without headache (p<0.001, p<0.001) and in chronic tension-type headache compared with migraine (p=0.01). Increasing slope (p<0.0001) and displacement towards lower pressures was found in the following order: no headache, migraine, frequent episodic tension-type headache, chronic tension-type headache. The displacement of the stimulus-response function was closely associated with frequency of headache. Finally, the stimulus-response function tended to be qualitatively altered in patients with frequent headache. The findings demonstrate, for the first time in a population-based study, a close relation between altered pain perception and chronification of headache, which most likely can be explained by central sensitization.