In the 1980s, health researchers discovered that childhood growth was influenced by socioeconomic status rather than race or ethnicity. In response, U.S. health providers phased out separate race-based growth curves and began to use a single reference curve instead.
A trio of RWJF scholars argues that health providers should get rid of race-based lung-function charts for the same reasons. Socioeconomic status affects lung function, and explains differences in lung function between racial groups to a greater degree than initially thought.
"Lung function is not physiologically fixed," said Sheryl Magzamen, PhD, MPH, a Robert Wood Johnson Foundation (RWJF) Health & Society Scholar (2007-2009) and an assistant professor in the College of Public Health at the University of Oklahoma Health Sciences Center. "There's no good medical reason to have separate reference equations for different racial groups."
In a recent study, Magzamen and her co-authors found that White adults who had completed high school—a proxy for socioeconomic status—had healthier lungs than Whites who had not completed high school. The same was true for Blacks, they found. Similar racial patterns were found with regard to college completion.
"We've been attributing poor normal lung function to a racial effect, when in fact, what we're seeing in large part appears to be the accumulated impact of socioeconomic factors," David Van Sickle, PhD, MA, also an RWJF Health & Society Scholar (2006-2008), explained in a recent news release.
Earlier Research Masks Influence of Socioeconomic Status on Lung Function
The finding breaks from previous research, which found that education and poverty explain only a small proportion of racial differences in adult lung function. But those earlier studies are skewed, Magzamen said, because they do not include smokers and, as a result, place a disproportionate emphasis on non-smokers, who tend to have higher education than smokers. Overemphasizing non-smokers masks the considerable effects of socioeconomic status on lung function, she said.
In previous studies, respondents were rejected if they had smoked 100 cigarettes, regardless of when the smoking occurred, Magzamen explained. But this type of analysis does not represent the underlying population and leads to bias, she and her co-authors wrote.
For the study, Magzamen, Van Sickle and co-author John Mullahy, PhD, a professor of population health science at the University of Wisconsin in Madison and co-director of the RWJF Health & Society Scholars program, analyzed lung function data from a national survey of health and nutrition. It was published in the September 1 issue of the American Journal of Respiratory and Critical Care Medicine and was accompanied by an editorial in the same issue.
"The importance of the present study is as much in the conceptual basis of how experimental subject groups need to be carefully chosen … as it is in the actual and specific findings reported," the editorial stated. "At the end of the day, socioeconomic status … appears to be an independent (and under-recognized) factor separate from race."
The relationship between low socioeconomic status and poor lung function merits further study, however, Magzamen said. It is unclear whether poorer lung function among adults who did not complete high school is related to higher rates of smoking, exposure to second-hand smoke, poor prenatal health, hazardous housing conditions or exposure to pollution from nearby roadways or other sites.
"We're trying to understand how the structure of our society contributes to development of illness," Magzamen said. "We need to think about the implications of socioeconomic status not only in economic terms but also in terms of the health and wellness of the population."