Purpose: Analgesics are commonly used drugs. The long-term effectiveness is mostly unproven, while the risk of several serious adverse effects is well established. We aimed to estimate the prevalence and incidence of persistent analgesic use and the association with chronic pain and sociodemographic and comorbid risk factors.
Methods: The Tromsø Study is an epidemiological, prospective study of health and diseases. We linked the sixth wave (Tromsø 6, 2007-08, n = 12,981) with the Norwegian Prescription Database (NorPD, 2004-13). Persistent analgesic use was defined as the use of analgesics, i.e., either non-steroidal anti-inflammatory drugs, opioids or paracetamol, for ≥90 days with proportion-of-days-covered ≥40 %. The study design provided both cross-sectional and longitudinal data; a cohort of 11,905 persons was followed for 4.5 years.
Results: The prevalence of persistent analgesic use was 4 % in general and 10 % among those reporting chronic pain. The incidence rate of persistent analgesic use was 21 per 1000 person-years in general. Baseline chronic pain doubled the risk of incident persistent analgesic use (HR = 2.05, 95 % CI 1.80-2.33). The risk increased with increasing chronic pain severity, as measured by chronic pain duration, frequency, intensity, and number of body locations. Sociodemographic risk factors were older age, female sex, lower education, and most likely lower physical activity. Psychological distress was not a statistical significant risk factor.
Conclusions: This study showed a relatively low prevalence of persistent analgesic use and that the majority of persons reporting chronic pain do not use analgesics persistently.
Keywords: Acetaminophen; Analgesics; Chronic pain; Non-steroidal anti-inflammatory agents; Opioids; Persistence; Pharmacoepidemiology.