Geographic variation in the utilisation of specialist healthcare for patients with substance use disorders in Norway: a population-based registry study.

PURPOSE: The purpose of this study is to analyse geographic variation in rates of patients and service utilisation for persons with substance use disorders (SUD) across Norwegian hospital catchment areas from 2017 to 2021, considering both outpatient and Inpatient care across substance use diagnosis. METHOD AND MATERIAL: This registry-based study used data from the Norwegian Patient Registry and Statistics Norway, covering 58,889 unique patients and 121,495 patient-years. Adjusted for age and sex this material yields a national SUD treatment rate of 14.0 per 1,000 over five years, on average 5.8 per year with a declining annual rate from 6.1-5.5. Analyses included diagnoses related to alcohol, opioids, cannabis, and other substances, excluding tobacco and opioid maintenance treatment. Three variation measures-Extreme Quotient (EQ), Coefficient of Variation (CV), and Systematic Component of Variation (SCV)-were used to assess disparities. RESULTS: Geographic variation in SUD treatment rates ranged from 3.6 to 11.5 per 1,000 inhabitants reaching a threefold difference between areas (EQ = 3.1). We found that SCV values (8.7-23.5) and SCV 5-95 (5.7-14.5) for diagnose groups and service type consistently exceeded the threshold of high and extremely high variation. Procurement of private services increased capacity significantly but did not markedly reduce variation. Variation remained extremely high even when the highest and lowest rates were excluded (SCV 13.8, SCV5-95 11.3). CONCLUSION: Patient rates in SUD treatment fell every year between 2017-2021 and the geographic variation was high to extremely high. Treatment of substance use disorders in Norway may require stronger regional governance to reduce unwarranted variation and ensure equitable access to treatment. Substantial reductions in variation can be achieved by i) redistributing capacity among catchment areas, ii) purchasing fewer and shorter Inpatient stays and iii) increasing outpatient treatment. In addition, such means could dramatically increase patient rates. There is a need for more consistent clinical practices and adjusted capacity for treating specific substance diagnoses.