Prevalence of abnormal spirometry and correlates of lung function decline among a population in rural Uganda

Chronic lung disease, which is the third leading cause of death globally, places a disproportionate burden of morbidity and mortality on sub-Saharan Africa, where limited infrastructure results in a lack of understanding of how lung function changes over time, whether it varies among susceptible populations, or whether at-risk individuals could be identified before abnormal lung function develops. To address this gap, we aimed to characterise lung function patterns and identify correlates of lung function decline in rural Uganda.

Adults completed health questionnaires and American Thoracic Society/European Respiratory Society-acceptable spirometry up to three times over four years (2015-2019). Our primary outcome was lung function (forced expiratory volume in 1 second (EV₁) and FEV₁/forced vital capacity (FVC)); our secondary outcome was spirometry patterns. We characterised baseline patterns using Global Lung Initiative (GLI)-Global prediction equations and identified correlates of decline using generalised mixed effects linear regression. We then explored effect modification by sex, smoking, and socioeconomic status using interaction terms, with inverse probability of treatment weights balancing baseline characteristics.

A total of 902 participants completed 1,471 ATS/ERS-acceptable spirometry tests. Their median age was 35 years, 56% were women, 75% were never-smokers, and 31% experienced chronic respiratory symptoms. Abnormal lung function affected 14% of the cohort, more commonly women and those with respiratory symptoms. FEV₁ declined by 10mL/year (95% CI = -17, -2), and FEV₁/FVC declined by 0.006/year (95% CI = -0.008, -0.005) or 0.53% predicted/year (95% CI = -0.68, -0.37). Among those with normal baseline lung function, FEV₁ and FEV₁/FVC declined more rapidly (FEV₁ -18mL/year; FEV₁/FVC -0.66% predicted). There was no effect modification by sex, smoking, or SES.

Lung function decline may be more rapid in this young, mostly non-smoking population. Our findings extend the understanding of non-obstructive lung disease in sub-Saharan Africa and emphasise that risk persists despite normal spirometry. These data can inform regional public health strategies for risk mitigation, early disease detection, and building healthcare infrastructure for the growing population at risk for or living with chronic lung disease.