Vitamin B12 Levels, Substance Use Patterns and Clinical Characteristics among People with Severe Substance Use Disorders: A Cohort Study from Western Norway

Abstract

People with severe substance use disorder (SUD) have a higher burden of micronutrient deficiency compared with the general population. The aim of this study was to investigate vitamin B12 status and risk factors of deficiency related to substance use, opioid agonist therapy (OAT), as well as hepatitis C infection and liver fibrosis. In this prospective cohort study, participants were recruited from outpatient OAT and SUD clinics in western Norway, and assessed annually with a clinical interview and exam, including venous blood sampling. Data were collected between March 2016 and June 2020, and a total of 2451 serum vitamin B12 measurements from 672 participants were included. The median serum vitamin B12 concentration was 396 (standard deviation 198) pmol/L at baseline, 22% of the population had suboptimal levels (<300 pmol/L) and 1.2% were deficient at baseline (<175 pmol/L). No clear associations were seen with substance use patterns, but liver disease and younger age were associated with higher vitamin B12 levels. Although the majority of participants had satisfactory vitamin B12 levels, about a fifth had suboptimal levels that might or might not be adequate for metabolic needs. Future studies could investigate potential gains in interventions among patients with suboptimal but non-deficient levels.

Keywords: Norway; liver disease; micronutrients deficiencies; opioid agonist therapy; substance use disorder; vitamin B12.

Figure 1

Distribution of vitamin B12 status in the first and second annual assessments. This figure displays the changes in vitamin B12 status categories from the first (left) to the second (right) assessment for participants with at least two vitamin B12 measurements.

Figure 2

Association of substance use severity with serum vitamin B12 concentration. The figure to the left was constructed using generalized additive models in R and displays of the associations of vitamin B12 concentration in serum with the substance use severity index. The solid line depicts the association at various severity scores, whereas the shaded area represents the 95% confidence interval of this association. The figure to the right displays the distribution of substance use severity scores in the population.