Co-morbidity in persistent opioid users with chronic non-malignant pain in Norway.
BACKGROUND
In patients with chronic non-malignant pain (CNMP), co-morbid physical or mental health disorders are common and may have a negative impact on health-related quality of life and treatment outcomes. The purpose of this study was to examine the occurrence of chronic psychiatric and somatic diseases in persistent opioid users with CNMP compared with the general population in Norway.


METHODS
In this cross-sectional study, prescription patterns of dispensed opioids were used to identify a study population of persistent opioid users with CNMP from the general population. Reimbursed prescriptions marked with diagnostic codes were used to identify the occurrence of 21 somatic and 3 psychiatric diseases for a 1-year period in the Norwegian Prescription Database. Occurrence of disease in persistent opioid users was compared to an age- and gender-specific population of all Norwegian residents aged 18-79 years in 2009. Standardized morbidity ratios (SMRs) for each disease were calculated.


RESULTS
Eighty-five percent of the persistent opioid user population had at least one co-morbid disease compared with 45% of the general population. Forty-two percent had three or more co-morbidities. SMRs in both men and women were generally increased except for dementia, glaucoma and renal disease, indicating a higher occurrence of disease in persistent opioid users.


CONCLUSIONS
A higher occurrence of both somatic and psychiatric co-morbidities in disease stages warranting pharmacological treatment was found in persistent opioid users with CNMP compared with the general population of Norway.
Department of Circulation and Medical Imaging, Pain and Palliation Research Group, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway; National Competence Centre for Complex Symptom Disorders, St. Olav's University Hospital, Trondheim, Norway.
A
A
Mellbye
Ø
Ø
Karlstad
S
S
Skurtveit
P C
PC
Borchgrevink
O M S
OM
Fredheim
D000293:Adolescent; D000328:Adult; D000368:Aged; D000701:Analgesics, Opioid / Q000627:therapeutic use*; D059350:Chronic Pain / Q000188:drug therapy* / Q000453:epidemiology*; D015897:Comorbidity; D003430:Cross-Sectional Studies; D016208:Databases, Factual; D011307:Drug Prescriptions; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology*; D008875:Middle Aged; D009664:Norway / Q000453:epidemiology; D055815:Young Adult
D000701:Analgesics, Opioid