Individual Characteristics, Not Pollution, Factor Into Which Women Develop ACOS

Lifestyle factors and individual characteristics, rather than air pollution, explain which women with asthma go on to develop chronic obstructive pulmonary disease (COPD), resulting in asthma and COPD overlap syndrome (ACOS), according to a new study published in the Annals of the American Thoracic Society.

Those who develop ACOS experience increased exacerbations, hospitalizations, and healthcare costs and have a lower quality of life compared with those who have asthma or COPD alone. Women have a higher prevalence of ACOS than men, as well as a higher mortality rate.

The research looked at women in Ontario who were part of another study from 1980 to 1985. They were linked to another health administrative database and followed from 1992 to 2015.

Satellite data were used to estimate the earth’s surface concentrations of fine particulate matter, a major air pollutant that penetrates deep into the lungs because of its microscopic size.

The primary outcome was time between first documented date of prevalent asthma and the date of incident COPD. Individuals were defined as having COPD if they were 35 years or older and had 1 or more COPD hospitalization and/or 1 or more COPD ambulatory care claim.

Of the 4051 women with asthma, 1701 (42%) developed COPD. On average, the women were followed for about 14 years after being diagnosed with asthma. The mean age at the study end date was 79 years.

Women who had a smoking history of more than 5 pack-years, meaning they had smoked more than the equivalent of a pack of cigarettes a day for 5 years, were much more likely to develop ACOS (62.3%) than those who smoked fewer cigarettes or never smoked.

The researchers were surprised that 38% of the women who developed ACOS in the study had never smoked.

In addition, 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, undertreatment of asthma, and poor compliance to medications, all of which lead to more frequent asthma attacks. These attacks in turn may lead to airway remodeling that increases the chances of developing ACOS.

Efforts are needed to improve asthma care, addressing both socioeconomic and geographic access to healthcare, the researchers said. In addition, health education and promotion efforts targeting smoking cessation, weight, and other issues need to be enhanced. Most of the risk factors for ACOS are modifiable, they said.

There were some limitations to the study. The researchers noted that they lacked the data to investigate this association directly. Study limitations also include not having information about exposure to secondhand smoke and exposure to air pollution over the entire time the women were followed.

Reference

To T, Zhu J, Gray N, et al. Asthma and COPD overlap in women: incidence and risk factors [published online July 17, 2018]. Ann Am Thorac Soc. doi: 10.1513/AnnalsATS.201802-078OC.