Sex Differences in COPD Slow to Be Recognized, Treated

Neil Osterweil, MDedge News

April 14, 2022

When Sigmund Freud claimed that "anatomy is destiny" he was referring to anatomical sex as a determinant of personality traits.

That notion has been widely discredited, but Freud appears to be inadvertently right in one respect: When it comes to chronic obstructive pulmonary disease (COPD), anatomy really is destiny, and sex may be as well, pulmonary researchers say.

There is a growing body of evidence to indicate that COPD affects men and women differently, and that men and women patients with COPD require different clinical management. Yet women are often underdiagnosed or misdiagnosed, partly because of poorly understood sex differences, but also because of cultural biases.

But plunging any farther into the weeds, it's important to define terAlthough various investigators have used the terms "sex" and "gender" interchangeably, sex is the preferred term when referring to biological attributes of individual patients, while gender refers to personal identity.

These distinctions are important, contended Amik Sodhi, MBBS, MPH, from the division of allergy, pulmonology, and critical care medicine at the University of Wisconsin–Madison.

"Sex is essentially a biologic construct, so it's got to do with the sex chromosomes, the genetics of that person, and it refers to the anatomic variations that can change susceptibility to different diseases," she said in an interview.

An example of sex differences or "sexual dimorphism" can be found in a recent meta-analysis of sex-based genetic associations by Megan Hardin, MD, MPH from Brigham & Women's Hospital in Boston and colleagues.

They reported that CELSR1, a gene involved in fetal lung development, was expressed more among women than among men and that a single nucleotide polymorphism in the gene was associated with COPD among women smokers, but not among men smokers.

The finding points to a potential risk locus for COPD in women, and could help shed light on sexual dimorphism in COPD, Hardin and colleagues said.

In contrast to sex, "gender is more of a psychosocial construct which can impact how diseases manifest themselves, how they are potentially managed, and what outcomes might occur for that particular disease," Sodhi said.

She and her colleagues recently published a review of sex and gender in common lung disorders and sleep in the journal CHEST, where they wrote that the "influence of sex and gender is portrayed in epidemiological data, disease pathogenesis and pathophysiology, clinical manifestations, response to treatment, access to care, and health outcomes. Hence, sex and gender should be considered in all types of research, clinical practice and educational curricula."

For example, as previously reported at the 2021 annual meeting of the American Thoracic Society, sex-specific differences in the severity of symptoms and prevalence of comorbidities in patients with COPD may point to different criteria for diagnosing cardiac comorbidities in women and men.

Those conclusions came from a retrospective analysis of data on 795 women and 1,251 men with GOLD (Global Initiative for Chronic Obstructive Lung Disease) class 1-3 disease.

The investigators looked at the patients' clinical history, comorbidities, lung function, COPD Assessment Test scores, and modified Medical Research Council (mMRC) dyspnea score, and found significant differences between men and women for most functional parameters and comorbidities, and for CAT items of cough, phlegm, and energy.

In logistic regression analysis, predictors for cardiac disease in men were energy, mMRC score, smoking status, body mass index, age, and spirometric lung function, but in women only age was significantly predictive for cardiac disease.

An example of gender effects on COPD differences in men and women is the increase in cigarette advertising aimed at women in the 1960s and the advent of women-targeted brands such as Virginia Slims, which in turn lead to increased smoking rates among women. In addition, in the developing world, where the sex/gender gap in COPD is narrowing, women tend to have greater exposure to wood smoke and cooking fuels in unventilated or poorly ventilated spaces, compared with men.

Increasing Incidence Among Women

According to the Centers for Disease Control and Prevention, chronic lower respiratory diseases, primarily COPD, were the fourth-leading cause of death in women in the United States in 2018, following only heart disease, cancer, and accidents/injuries.

And as a CDC analysis of data from the 2013 Behavioral Risk Factor Surveillance System showed, women were more likely to report being told by a physician that they had COPD than did men (6.6%, compared with 5.4%).

Sodhi and colleagues noted that, at all time points examined from 2005 to 2014, women had a higher proportion than men of COPD hospitalizations and in-hospital deaths. They also noted that female sex is associated with a threefold risk for severe early-onset COPD, and that women with COPD have lower diffusion capacity of lungs for carbon monoxide, despite having higher predicted forced expiratory volume in 1 second, compared with men.

"Historically, COPD wasn't a disease that was so prevalent in women. It's been in the past 20 years that the trends have changed," said Patricia Silveyra, MSc, PhD, ATSF, associate professor of environmental and occupational health at the University of Indiana, Bloomington.

The increasing prevalence of COPD among women cannot be explained by smoking alone, she said in an interview.

"It used to be thought that it was because more women smoked, but actually a lot of women who don't smoke can develop COPD, so it appears to be probably something environmental, but because it used to be a disease of older men, in the clinic there was also a bias to diagnose men with COPD, and women with asthma, so a lot of women went underdiagnosed," Silveyra said.

In their review, Sodhi and colleagues noted that women with COPD "may be underdiagnosed as a result of having different symptoms from those classically recognized. Reasons for underdiagnosis or a delay in diagnosis may also be due to lack of a formal evaluation with spirometry, women seeking care later in the course of disease, physician bias, or associated fatigue or depression misdirecting diagnostic strategies. Underdiagnosis may be associated with psychological distress and worse health-related quality of life."

Although the evidence is mixed, women tend to present more frequently with the chronic bronchitis phenotype of COPD, compared with the emphysema phenotype, and women tend to have greater degrees of pulmonary function impairment when exposed to tobacco smoke, even after controlling for differences in height and weight.

"For the same amount of exposure to tobacco smoke, females are likely to develop more severe airflow limitation at an earlier age than males, and have more exacerbation," Sodhi and colleagues wrote.

Both Silveyra and Sodhi said that reason why men and women differ in their physiological reactions to smoke are still unknown.

Sex Differences in Drug Responses

There is only limited evidence to indicate that women and men respond differently to various therapeutic agents, but what is clear is that more research into this area is needed, Sodhi and Silveyra said.

For example, among the few studies that have documented sex differences, one showed no sex differences in the efficacy of salmeterol/fluticasone combination therapy for reducing exacerbations or improving quality of life, whereas another showed that women were more likely than men to experience COPD symptoms or exacerbations after stopping inhaled corticosteroids, Sodhi and colleagues noted.

Both Sodhi and Silveyra emphasized the need for clinical trials that study the effects of sex on treatment outcomes in COPD, which could lead to better, more personalized therapeutic regimens that take sex and gender into account.

Sodhi and colleagues offered the following advices to clinicians: "Interaction with female patients should take into account that their symptoms may not conform to traditionally accepted presentations. Challenges exist for female patients at all levels of health care interaction and as clinicians we need to acknowledge the bias and willfully work toward recognition and elimination of unconscious and conscious bias. Empowering our patients to have frank discussions with their health care team when they perceive bias is another step to help promote equity."

The review by Sodhi and colleagues was supported by grants from the National Institutes of Health. Sodhi and Silveyra reported having no conflicts of interest to disclose.

This article originally appeared in Chest Physician.


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