More than 4 in 10 individuals with asthma run the risk of developing chronic obstructive pulmonary disease (COPD), a group of lung diseases that block airflow and make it harder to breathe, says a new study involving around 4,000 women.
The researchers examined risk factors for developing asthma and COPD overlap syndrome, known as ACOS.
The findings, published in the journal Annals of the American Thoracic Society, showed 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 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 as the researchers found that 38 per cent of the women who developed ACOS in the study had never smoked.
The study also identified obesity, rural residence, lower education levels and unemployment as significant risk factors for ACOS.
The authors believe that these factors 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.
"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 Teresa To, Professor at 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," To added.