Associations between lung function and future cardiovascular morbidity and overall mortality in a predominantly First Nations population: a cohort study.

Background: Spirometric lung function impairment is an independent predictor of respiratory and cardiovascular disease, and mortality across a broad range of socioeconomic backgrounds and environmental settings. No contemporary studies have explored these relationships in a predominantly regional/remote First Nations population, whose health outcomes are worse than for non-First Nations populations, and First Nations people living in urban centres. Methods: This was a retrospective cohort study of 1,734 adults (1,113 First Nations) referred to specialist respiratory outreach clinics in the state of Queensland, Australia from February 2012 to March 2020. Regression modelling was used to test associations between lung function and mortality and cardiovascular disease. Findings: At the time of analysis (August 2020), 189 patients had died: 88 (47%) from respiratory causes and 38 (20%) from cardiovascular causes. When compared to patients with forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) Z-scores of >0 to -1, patients with Z-scores <-1 were at elevated mortality risk (HR=3•2, 95%CI 1•4-7•4; HR=2•6, 95%CI 1•3-5•1), and elevated cardiovascular disease risk (OR=1•5, 95%CI 1•1-2•2; OR=1•6, 95%CI 1•2-2•3). FEV1/FVC% Z-scores <-1 were associated with increased overall mortality (HR=1•6, 95%CI 1•1-2•3), but not cardiovascular disease (OR=1•1, 95%CI 0•8-1•4). These associations were not affected by First Nations status. Interpretation: Reduced lung function even within the clinically normal range is associated with increased mortality, and cardiovascular disease in First Nations Australians. These findings highlight the importance of lung function optimisation and inform the need for future investment to improve outcomes in First Nations populations. Funding: None.