Objective: To evaluate the Severity of Dependence Scale (SDS) in people with primary chronic headache and analyze pattern of medication overuse.
Design: Cross-sectional epidemiological survey. A posted questionnaire screened for chronic headache. Neurological residents interviewed those with self-reported chronic headache. The International Classification of Headache Disorders was used. Split file methodology was employed for data analysis.
Setting: Akershus University Hospital, Oslo, Norway.
Participants: A random sample of 30 000 people, 30-44 years, from the general population of Akershus County, Norway. 405 people had primary chronic headache.
Main outcome measure: SDS score in those with and without medication overuse.
Results: The screening questionnaire response rate was 71%, the participation rate of the interview 74%. Among 405 people with primary chronic headache, 95% had chronic tension-type headache, 4% had chronic migraine, and <1% had other primary chronic headaches. Of 386 persons with chronic tension-type headache, 44% had medication overuse and 47% had co-occurrence of migraine. Simple analgesics, combination analgesics, triptans, ergotamine, opioids and combination of acute medications were overused by 65%, 27%, 4%, <1%, 1% and 2%, respectively. The mean SDS score was significantly higher in those with than without medication overuse (5.6 vs. 2.7; p<0.001).
Conclusion: The SDS questionnaire detects medication overuse and dependency-like behaviour in persons with primary chronic headache.
Key words: Epidemiology; headache; chronic headache; chronic tension-type headache; medication-overuse headache; general population; dependency; SDS