Heroin users have a high burden of respiratory morbidity, including premature lung function impairment. Further, methadone treatment has been found to aggravate lung function impairment and can independently cause asthma. However, the lung function status among heroin users on medication-assisted therapy (MAT) in Tanzania is yet to be studied. This study aimed to assess the magnitude, pattern and factors associated with lung function impairment among heroin users on MAT.

This was a quantitative, analytical cross-sectional study.

This study was conducted at MAT Clinic at Muhimbili National Hospital in Dar-es-Salaam, Tanzania.

Individuals aged 18 years or above with heroin use disorder on stable dose of methadone without heroin withdrawal symptoms (Maintenance Phase of Treatment) were recruited.

Participants were enrolled through systematic sampling technique. Data were collected using a questionnaire, and lung functions were measured using a spirometer. Lung function impairment was defined as the percentage of participants with forced expiratory volume in 1 s (FEV1)

We enrolled 302 participants into the study (mean age of 42.78±7.56 years). Lung function impairment was observed in 28.5% of participants, with an average age of 44±8 years. Restrictive lung disease was the most common pattern of lung function impairment affecting 13.2% of the participants. The predictors of lung function impairment were being underweight (OR) 4.73, 95% CI) 2.61–8.59, p

Heroin users on MAT have a high magnitude of lung function impairment. Routine lung function testing is recommended.