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Nearly half of women with asthma may develop COPD

More than 4 in 10 women with asthma may go on to develop chronic obstructive pulmonary disease (COPD), according to a study conducted in Ontario, Canada. In the study, Dr Teresa To and co-authors report that of the 4,051 women with asthma included in their study, 1,701, or 42%, developed COPD. On average, the women were followed for about 14 years after being diagnosed with asthma.

The researchers examined risk factors for developing asthma and COPD overlap syndrome, known as ACOS. Those who develop ACOS experience increased exacerbations and hospitalisations and have a lower quality of life, compared to those who have asthma or COPD alone.

"Previous studies have found an alarming rise in ACOS in women in recent years and that the mortality rate from ACOS was higher in women than men," said To, a professor in the Graduate School of Public Health at the University of Toronto in Canada. "We urgently need to identify and quantify risk factors associated with ACOS in women to improve their health and save lives."

The authors report that individual risk factors played a more significant role in the development of ACOS than exposure to fine particulate matter, a major air pollutant that because of its microscopic size penetrates deep into the lungs.

Women who had a more than five-pack-year smoking history, meaning they had smoked more than the equivalent of a pack of cigarettes a day for five years, were much more likely to develop ACOS than those who smoked fewer cigarettes or never smoked.
However, ACOS did not affect only those who smoke: 38% of the women who developed ACOS in the study had never smoked.

In addition to smoking, the study identified obesity, rural residence, lower education levels and unemployment as significant risk factors for ACOS. The authors speculate that these factors indicative of low socioeconomic status may result in suboptimal access to care, under-treatment of asthma and poor compliance to medications, all of which lead to more frequent asthma attacks. These attacks in turn may lead to airway re-modeling that increases the chances of developing ACOS.

The researchers noted that they lacked the data to investigate this association directly. Study limitations also include not having information about exposure to second-hand smoke and exposure to air pollution over the entire time the women were followed.
The authors wrote that they were encouraged by the fact that most of the risk factors identified in their study were modifiable.

"The adverse impact of smoking and obesity on health may be even worse in those who are already living with asthma or COPD," said To, who is also senior scientist, Child Health Evaluative Sciences, at The Hospital for Sick Children (SickKids). "Identifying modifiable risk factors in the progression from asthma to COPD is an essential first step in developing prevention strategies that lead to a healthy, active lifestyle."

Rationale: Women with asthma are at a high risk of developing 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.
Objective: To quantify the risk of developing COPD in Ontario women with asthma and identify factors that are associated with increased risk.
Methods: Data for Ontario women with asthma who participated in the Canadian National Breast Screening Study from 1980─1985 were linked to health administrative databases and participants were followed from 1992─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.
Results: 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 old. Low education, high body mass index, rurality, and high levels of cigarette smoking were associated with ACOS incidence, while exposure to fine particulate matter (PM2.5), a major air pollutant, was not.
Conclusion: 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.

Teresa To, Jingqin Zhu, Natasha Gray, Laura Y Feldman, Paul J Villeneuve, Christopher Licskai, Andrea Gershon, Anthony B Miller

[link url=""]American Thoracic Society material[/link]
[link url=""]Annals of the American Thoracic Society abstract[/link]

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