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Four in 10 women with asthma may develop COPD

Individual risk factors play a more significant role in the development of ACOS than exposure to fine particulate matter

Ingrid Torjesen

Monday, 13 August 2018

More than four in 10 women with asthma may go on to develop chronic obstructive pulmonary disease (COPD), according to a study* published online in the Annals of the American Thoracic Society.

Researchers accessed data on women who participated in the Canadian National Breast Screening Study from 1980─1985 which were linked to health administrative databases and participants were followed from 1992─2015.

A total of 4,051 women with asthma were identified and included in the study, of whom 1,701 (42%) developed COPD.

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

The authors report that individual risk factors played a more significant role in the development of ACOS than exposure to fine particulate matter (PM2.5), 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 per cent 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 remodelling that increases the chances of developing ACOS.

The study lacked data to investigate this association directly, and also did not include information about exposure to second-hand smoke and exposure to air pollution over the entire time period over which the women were followed.

"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. We urgently need to identify and quantify risk factors associated with ACOS in women to improve their health and save lives,” said Dr To, a professor in the Graduate School of Public Health at the University of Toronto in Canada.

He added that it was encouraging that most of the risk factors identified in the 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," he said.

"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."

*To T, Zhu J, Gray N, et al. Asthma and COPD Overlap in Women: Incidence and Risk Factors. Annals of the American Thoracic Society. Doi: 10.1513/AnnalsATS.201802-078OC

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