# Characteristics and comorbidities of patients on opioid agonist therapy in Switzerland: A descriptive analysis of the nationwide SAMMSU cohort

## TL;DR

This study describes the health and aging trends of Swiss patients on opioid treatment, highlighting the need for broader chronic care.

## Contribution

The paper provides a nationwide analysis of OAT patients in Switzerland, revealing shifts in treatment and increasing chronic health issues.

## Key findings

- Ongoing illicit drug use declined, while OAT shifted to long-acting morphine and diacetylmorphine.
- Over half of patients showed polypharmacy, often involving psychotropic drugs.
- OAT services must transition to comprehensive chronic care for an aging, multimorbid population.

## Abstract

Opioid agonist therapy (OAT) is the gold standard of treatment for opioid dependence and a cornerstone of Swiss drug policy. The Swiss Association for the Medical Management in Substance Users (SAMMSU) cohort was established to monitor health trends and improve care for OAT patients across Switzerland.

Baseline and follow-up data collected from eight centres between 2014 and 2024 were analysed descriptively, including demographic and psychosocial characteristics, substance use history, prescribed OAT, co-medications, and somatic and psychiatric comorbidities.

During the study, the SAMMSU cohort included 1 502 participants. Median individual age at registration was 44.3 years, rising to a cohort median of 50.9 years by the end of 2024; 75.7 % of participants were male. Lifetime heroin use was reported by 97.2 %, with 73.2 % having a history of intravenous drug use. Ongoing illicit and intravenous drug use declined over time, while prescribed OAT shifted from methadone to long-acting morphine and diacetylmorphine. The most prevalent lifetime somatic comorbidities were hepatitis C (56.5 %), (pre)hypertension (18.6 %), musculoskeletal disorders (13.8 %), and needle abscesses (13.7 %). Psychiatric disorders – primarily affective (34.8 %), personality (23.2 %), and anxiety disorders (18.0 %) – contributed to multimorbidity and a high prevalence of polypharmacy (49.2 %). There were 120 deaths, mainly from malignancy, overdose, and liver failure, with a median age at death of 51.6 years.

SAMMSU cohort trends corroborate the effectiveness of OAT in reducing illicit drug use and underscore the need for OAT services to evolve from an addiction-focused model to comprehensive chronic care for an ageing and highly vulnerable population.

•The ageing OAT cohort increasingly shows a chronic multimorbidity profile.•Hypertension, diabetes, COPD, and osteoporosis appear at markedly younger age.•Mood disorders and schizophrenia drive the cohort’s high psychiatric comorbidity.•Over half of OAT patients exhibit polypharmacy, often including psychotropic drugs.•OAT services must evolve from addiction-focused to comprehensive chronic care.

The ageing OAT cohort increasingly shows a chronic multimorbidity profile.

Hypertension, diabetes, COPD, and osteoporosis appear at markedly younger age.

Mood disorders and schizophrenia drive the cohort’s high psychiatric comorbidity.

Over half of OAT patients exhibit polypharmacy, often including psychotropic drugs.

OAT services must evolve from addiction-focused to comprehensive chronic care.