BACKGROUND: This study examined the patterns of medical comorbidities among aging people who use drugs (PWUD) enrolled in a heroin-assisted treatment (HAT) program in Bern, Switzerland, over ten years.

METHODS: Cross-sectional assessments were conducted at a single HAT center in 2009 (n = 200), 2012 (n = 215), and 2019 (n = 203). A group of long-term participants (n = 102) present at all three time points was identified and compared to other participants over time. Data on demographics; infectious, psychiatric, and medical comorbidities; substance use; and opioid agonist treatment (OAT) were analyzed using descriptive statistics and logistic regression.

RESULTS: In 2019, the median age of long-term participants was 52 years, one-third of patients were women. Hepatitis C virus (HCV) RNA positivity declined from 50/102 (49%) in 2009 to 10/102 (9.8%) in 2019, whereas HIV prevalence remained stable at 12% with high treatment uptake. Medical multimorbidity (≥2 medical comorbidities) increased from 8.8% to 37.3% ( < 0.001), with cardiovascular and musculoskeletal diseases being the most common comorbidities. In 2019, non-long-term participants were younger (median 42 years) with lower multimorbidity (16.8% vs. 37.3%,  = 0.008). Ongoing use of non-prescribed drugs (odds ratio (OR) 2.49; 95% confidence interval (CI) 1.17-5.28;  = 0.018) and advancing age (OR 1.08; 95% CI 1.03 - 1.14;  = 0.002) independently predicted multimorbidity in 2019.

CONCLUSIONS: Over 10 years, prevalence of active HCV infection among PWUD in long-term HAT declined, whereas non-communicable diseases increased. Integrated care models combining OAT with medical services are essential to meet the evolving health needs of this population.