Women face higher risk of COPD even without smoking history

Women' are around 50% more likely than men to develop COPD, the umbrella term for chronic lung conditions, such as emphysema and bronchitis, even if they have never smoked or smoked much less than their male counterparts, suggests observational research, published in the open access journal BMJ Open Respiratory Research.

The findings challenge the widely held belief that women's increased vulnerability to cigarette smoke likely explains this disparity, conclude the researchers.

Smoking is the principal cause of COPD. But despite significant falls in cigarette smoking over the past 50 years, it remains a leading cause of death in the USA, with the prevalence of COPD in women approaching that of men, say the researchers. 

Women with COPD tend to have more severe symptoms, and at a younger age, than their male counterparts, prompting the suggestion that the explanation may lie in a heightened susceptibility to the effects of cigarette smoke, explain the researchers.

To clarify the associations between gender, cigarette smoke, and COPD, and to update previous estimates of the prevalence and impact of COPD, the researchers drew on a large nationally representative US survey of adults from the 2020 National Health Interview Survey (NHIS). 

Respondents (12,638 women and 10,390 men aged at least 40) were asked about their smoking history, what tobacco products they used, and whether they vaped.

Women reported lower rates of both current and former cigarette, cigar, and pipe smoking, and smokeless tobacco use than men, but similar rates of vaping.

The prevalence of COPD was just under 8% for women and 6.5% for men. Women with COPD were more likely to have never smoked cigarettes than men with COPD (26.5% vs just over 14%), and less likely to use other tobacco products except for e-cigarettes (26.5% vs 20%).

Women also reported smoking fewer daily cigarettes than men, averaging around 18 compared with around 22, and to have done so for fewer years. And they were less likely than men to have started smoking before the age of 15:19% vs 28%.

Yet the prevalence of COPD was higher among women who had ever smoked than it was among men: 16% vs 11.5%. And among women who had never smoked the prevalence of COPD was almost twice as high as it was in male non-smokers: just over 3% compared with just over 1.5%. 

In further analysis, female gender was associated with a significantly (47%) higher risk of being diagnosed with COPD after accounting for potentially influential factors. 

This gender difference in risk persisted, irrespective of smoking history: among those who had never smoked, women were 62% more likely to be diagnosed with COPD, and among those who had ever smoked they were 43% more likely to do so. 

The researchers acknowledge that their study relied on self report rather than objectively measured data. And they lacked potentially important information on hormonal influences, family history, or infectious, occupational, and environmental exposures.

But they nevertheless suggest: "These findings should raise questions about whether differing susceptibility to tobacco smoke is the key factor driving the increased COPD prevalence in women in the USA. 

"If women were more susceptible to the effects of smoking, we would not expect to see a nearly identical risk per 10 pack-year exposure, nor would we expect to see a similarly increased relative risk among those who had never smoked." 

And they conclude: "Our findings refine prior estimates of COPD among those without a smoking history and re-emphasise the high burden of COPD in women, underscoring the need for thoughtful efforts to prevent, diagnose, and treat their disease."