Abstract
BACKGROUND: Although associations between chronic obstructive pulmonary disease (COPD) or ischaemic heart disease (IHD) and lifestyle factors or air pollution factors (referred as LAFs below) are well-established, it is unclear the influences of LAFs on the trajectory of IHD and COPD multimorbidity (referred as ICM below). Therefore, this study investigated the influences of LAFs on the trajectory of ICM from healthy to IHD or COPD, to ICM, and to all-cause death. METHODS: A cohort of 339,213 participants from the UK Biobank aged 37-73 who were free of IHD and COPD were included. A multi-state model was used to analyse the influences of high-risk factors including current smoking or quitting due to illness or physician's advice, current excessive alcohol drinking, physical inactivity, unhealthy body shape, and excessive air pollution with particulates matter with an aerodynamic diameter ≤2.5 μm (PM(2.5)) on ICM trajectory. RESULTS: During a median follow-up of 13.74 years, 46,398 participants developed IHD or COPD (referred as IOC below), 3949 developed ICM, and 35,691 died from any cause. All five high-risk factors played crucial but different roles in these transitions. The hazard ratios (95 % confidence intervals) per one-factor increase were 1.29 (1.27-1.3), 1.38 (1.33-1.44), and 1.69 (1.56-1.84) for transitions from baseline to IOC, from IOC to ICM, and from baseline to ICM and 1.19 (1.17-1.21), 1.18 (1.15-1.21), and 1.12 (1.05-1.19) for mortality risk from baseline to all-cause death, from IOC to all-cause death, and from ICM to all-cause death, respectively. CONCLUSIONS: Our study revealed that LAFs have a stronger impact on morbidity outcomes than on morbidity outcomes. These findings provide evidence to develop strategies for managing the trajectory of ICM.