Women with asthma are at a high risk of developing chronic obstructive pulmonary disease (COPD) or asthma and COPD overlap syndrome (ACOS) as they age, which is a condition associated with a high mortality rate, low quality of life, and high healthcare costs. However, factors influencing the development of ACOS remain unclear.To quantify the risk of developing COPD in women in Ontario with asthma and identify factors that are associated with increased risk.Data for women in Ontario with asthma who participated in the Canadian National Breast Screening Study from 1980 to 1985 were linked to health administrative databases, and participants were followed from 1992 to 2015. A competing risks survival model was used to measure the associations between sociodemographic, lifestyle, and environmental risk factors and time to COPD incidence, accounting for death as a competing risk.A total of 4,051 women with asthma were included in the study, of whom 1,701 (42.0%) developed COPD. The mean age at the study end date was 79 years. Low education, high body mass index, rurality, and high levels of cigarette smoking were associated with ACOS incidence, whereas exposure to fine particulate matter, a major air pollutant, was not.Individual risk factors appear to play a more significant role in the development of ACOS in women than environmental factors, such as air pollution. Prevention strategies targeting health promotion and education may have the potential to reduce ACOS incidence in this population.
