Published On October 20, 2022
In the mid-1800s, physician Samuel Cartwright undertook the first studies of lung function in people of different races. Using the recently invented spirometer, which measures the amount of air someone is able to breathe in and out, he noted a 20% deficit in the lung capacity of enslaved Black people compared to that of white people. Instead of concluding that being enslaved might not be ideal for lung health, Cartwright—unabashedly pro-slavery—attributed this difference to innate racial deficiencies.
More than 150 years later, the idea that lung function varies according to race endures. Race is still built into calculations to determine whether a person’s lung function is normal or disordered. As race-based metrics throughout medicine have drawn attention, in particular for their ability to perpetuate inequality, a new wave of research is looking at spirometry and its basic assumptions.
Spirometry remains an essential means of testing for pulmonary disease, used currently to diagnose asthma, chronic obstructive pulmonary disease (COPD) and other lung disorders. So guidelines saying that the norm for Black and white patients are essentially different can have profound effects. Daniel Colón Hidalgo, a fellow in Pulmonary Sciences and Critical Care Medicine at the University of Colorado Anschutz, notes that a Black patient who scores lower than a white patient could still be considered to have normal lung function—and thus might be delayed in receiving needed care for a lung condition.
Data has been used to support the continued use of these innate racial differences. Assessments of lung function in more than 20,000 people in the National Health and Nutrition Examination Survey III (NHANES III, which concluded in 1994), for instance, suggested that values for Black Americans were about 12% to 15% lower than for white people.
But many have argued that these differences, rather than being innate or genetic, have better explanations. “In medicine, we tend to use race as an easy surrogate for a bunch of other things,” says Colón Hidalgo, who cites childhood nutrition, pollution and exposure to smoking among other factors that may affect lung function.
Bolstering this argument, no gene or group of genes can, as yet, explain apparent racial differences in lung function. In contrast, many environmental factors that have been proven to affect lung function often disproportionately affect people of color. Research has shown that in the United States, people who are Black, Hispanic or Asian are exposed to higher levels of air pollution than white people, for example.
A recent study also showed that using racial assumptions about normal lung function may not actually help predict health outcomes. The 2022 study of more than 3,000 people of various races found that race-based equations were no better than equations that didn’t include race in determining chronic lower respiratory disease-related hospitalizations or deaths.
There is also substantial potential for harm, especially when racial classifications lead to underdiagnosis and lack or delay of treatment. In an abstract presented at the 2021 American Thoracic Society Conference, Alexander Moffett, a fellow in Pulmonary and Critical Care Medicine at the University of Pennsylvania, showed with his fellow researchers that in a cohort of approximately 14,000 Black patients, removing race correction would have led to 414 more diagnoses of obstructive lung disease and 665 more of restrictive lung disease.
Moffett believes that failing to understand the impact of environmental exposures is a major problem for the reference data sets that are used to determine what is “normal” for different races. “Not controlling for many kinds of exposure can effectively reproduce historical sources of disparity by normalizing what has been, in fact, the product of systemic racism,” says Moffett.
Yet despite growing concern that lung function testing needs to be reexamined, the medical community has been slow to change, says Colón Hidalgo.
Some steps have been taken. In March of 2022, the American Thoracic Society and European Respiratory Society issued an update on pulmonary function testing which stated, “The historical approach of fixed adjustment factors for race is not appropriate and is unequivocally discouraged. As there are observed population differences in body proportions and lung function, in some contexts it may be relevant to interpret results for an individual relative to that of a similar ancestral grouping, whereas in others it may be more appropriate to compare to the whole population.”
Moffett feels this guidance is still murky. “I don’t think anyone who uses ‘race’ in clinical medicine today has any idea what ‘race’ is supposed to represent,” he says. “I am not sure that ‘ancestral grouping’ is any more clear than ‘race,’ or that our current use of ‘race’ captures anything so precise.”
Colón Hidalgo says that while there have been some proposals for change published in medical journals, “none of them, in my opinion, is yet strong enough to lead to widespread improvement.” More research demonstrating the harms to patients will be needed, he says, to convince the pulmonary medicine community to end the practice.
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