National study of discontinuation of long-term opioid therapy among veterans.

Veterans have high rates of chronic pain and long-term opioid therapy (LTOT). Understanding predictors of discontinuation from LTOT will clarify the risks for prolonged opioid use and dependence among this population. All veterans with at least 90 days of opioid use within a 180-day period were identified using national Veteran's Health Affairs (VHA) data between 2009 and 2011. Discontinuation was defined as 6 months with no opioid prescriptions. We used Cox proportional hazards analysis to determine clinical and demographic correlates for discontinuation. A total of 550,616 veterans met criteria for LTOT. The sample was primarily male (93%) and white (74%), with a mean age of 57.8 years. The median daily morphine equivalent dose was 26 mg, and 7% received high-dose (>100mg MED) therapy. At 1 year after initiation, 7.5% (n=41,197) of the LTOT sample had discontinued opioids. Among those who discontinued (20%, n=108,601), the median time to discontinuation was 317 days. Factors significantly associated with discontinuation included both younger and older age, lower average dosage, and having received less than 90 days of opioids in the previous year. Although tobacco use disorders decreased the likelihood of discontinuation, co-morbid mental illness and substance use disorders increased the likelihood of discontinuation. LTOT is common in the VHA system and is marked by extended duration of use at relatively low daily doses with few discontinuation events. Opioid discontinuation is more likely in veterans with mental health and substance use disorders. Further research is needed to delineate causes and consequences of opioid discontinuation.