Objectives: To examine the prevalence of chronic headache (> or =15 days/month) associated with analgesic overuse in relation to age and gender and the association between analgesic overuse and chronic pain (i.e., migraine, nonmigrainous headache, neck and low-back pain).
Methods: In the Nord-Trøndelag Health Study 1995 to 1997 (HUNT-2), a total of 51,383 subjects responded to headache questions (Head-HUNT), of which 51,050 completed questions related to musculoskeletal symptoms and 49,064 questions regarding the use of analgesics.
Results: The prevalence of chronic headache associated with analgesic use daily or almost daily for > or =1 month was 1% (1.3% for women and 0.7% for men) and for analgesic overuse duration of > or =3 months 0.9% (1.2% for women and 0.6% for men). Chronic headache was more than seven times more likely among those with analgesic overuse (> or =1 month) than those without (odds ratio [OR] = 7.5, 95% CI: 6.6 to 8.5). Upon analysis of the different chronic pain subgroups separately, the association with analgesic overuse was strongest for chronic migraine (OR = 10.3, 95% CI: 8.1 to 13.0), intermediate for chronic nonmigrainous headache (OR = 6.2, 95% CI: 5.3 to 7.2), and weakest for chronic neck (OR = 2.6, 95% CI: 2.3 to 2.9) and chronic low-back (OR = 3.0, 95% CI: 2.7 to 3.3) pain. The association became stronger with increasing duration of analgesic use for all groups and was most evident among those with headache, especially those with migraine.
Conclusions: Chronic headache associated with analgesic overuse is prevalent and especially chronic migraine is more strongly associated with frequent intake of analgesics than other common pain conditions like chronic neck and chronic low-back pain.