Incidence and determinants of CoVID-19 in patients seeking treatment of Substance Use Disorder: a population-based linkage study

It was hypothesized at the beginning of the COVID crisis, that people with substance use disorder (SUD) would be exposed to a higher risk of COVID-19 infection. However, there is little evidence regarding the incidence and determinants associated with infection among this group. The aims of the study are to determine the cumulative incidence (AI) and the determinants associated with COVID-19 infection.

This is a population-based retrospective observational study. The study population is people who started treatment for SUD (N=23,124) in public health centres in 2018 and 2019. We calculated the adjusted incidence (AI) of COVID-19 confirmed by PCR (polymerase chain reaction) during 2020, according to sex and type of substance used. Finally, we constructed a log binomial generalized linear model (GLM) with log link, to estimate, using relative risk, the strength of association between study variables and infection. Of the 23,124 persons who initiated treatment for SUD, 601 were infected with COVID-19, confirmed by PCR test. Those who started treatment for alcohol use had a statistically higher risk of infection, with an AI of 3.00% (95% CI: 2.70 -3.33), than those who started treatment for heroin use, AI [1.94% (95% CI: 1.47 -2.55)]. Being a migrant, living in institutionalized centres, having HIV, and having a high comorbidity, were associated with a higher risk of infection. The incidence of COVID-19 in people with SUD in Catalonia during 2020 was not higher than in the general population.