Head or neck injury increases the risk of chronic daily headache - A population-based study

Objective: To evaluate the extent to which head and neck injury ( HANI) contributes to chronic daily headache ( CDH). Background: In prospective studies, head injury is associated with headache ( HA) that remains a problem at 12 to 24 months post- head injury in 20 to30% of patients. Of these, up to 30 to 50% manifest CDH. The degree to which head injury contributes to CDH has not been evaluated in a non- clinical population. We evaluate the relationship between lifetime occurrence of HANI and CDH in a randomly chosen population sample. Methods: Study participants are from the Frequent Headache Epidemiology Study. Cases with CDH ( >= 180 HA/ year) and a comparison group with episodic headache ( EH, 2 to 102 HA/ year) were identified from the general population. Subjects were asked about lifetime occurrence of HANI. HANI were further classified as potentially precipitating injuries ( PPI) if they occurred within 2 years of CDH onset for cases or in an equivalent 2- year period for EH controls. Results: Lifetime occurrence of HANI was more frequent in cases than controls for men ( adjusted OR = 3.1 [ 1.3 to 7.2]), women ( OR = 1.5 [ 0.97 to 2.3]), and overall ( OR = 1.7 [ 1.1 to 2.4]). The attributable risk was 15% ( 36% men, 11% women). Results were similar for PPI. The odds of CDH increased with the number of lifetime HANI in all groups ( p < 0.05 trend). Conclusions: Results suggest that head and neck injury ( HANI) accounts for approximately 15% of chronic daily headache ( CDH) cases in this non- clinical population. The relationship between HANI and CDH was not limited to injuries proximate to CDH onset. The lifetime risk of CDH increases with increasing number of HANI.