High magnitude of lung function decline among heroin users attending Medication- Assisted Therapy clinic at Muhimbili National Hospital, Tanzania

Heroin users have a high burden of respiratory morbidity, including premature lung function decline at age of 41 years. This early decline in lung function has been attributed to exposure to multiple risk factors. Further, methadone treatment has been found to aggravate lung function decline and independently cause asthma. However, the lung function status among heroin users on Medication-Assisted Therapy clinic in Tanzania is yet to be studied. This study aimed to assess the magnitude, pattern, and factors associated with lung function decline among heroin users attending MAT clinic at the Muhimbili National Hospital in Dar-es-salaam, Tanzania. This was a quantitative, analytical cross-sectional study conducted between May, 2022 - July, 2023. Individuals aged 18 years or above with heroin use disorder on the maintenance phase of treatment were recruited into the study. Data were collected using a questionnaire, and lung functions were measured using a portable spirometer. Lung function decline was defined as the percentage of participants with FEV1 <70%. The association between socio-demographic characteristics, substance use history and comorbidities with lung function decline was assessed via binary logistic regression. We enrolled 302 participants into the study (mean age of 42.78{+/-}7.56 years), whereby 95.7% were male. Of the study participants, 28.5% had lung function decline with mean age at onset of 44 {+/-}8 years. Restrictive lung disease was the commonest pattern of lung function decline with a proportion of 13.2%. Independent predictors of lung function decline were being underweight (aOR 4.73, 95% CI 2.61-8.59, p<0.001), living with HIV infection (aOR 2.61, 95% CI 1.20-5.66, p=0.016) and having a history of pulmonary TB (aOR 2.48, 95% CI 1.48-4.17, p=0.001). Heroin users on methadone therapy in Dar-es-salaam have high magnitude of lung function decline compared to the general population. Routine lung function testing is recommended.