LAUSR

never-smokers (3). This study has limitations, some of which highlight the unique challenges of studying rural COPD. Although NHANES was designed to be representative of U.S. demographics, it does not sample all 50 states. Rural residents faced a greater burden of COPD in the West, Midwest, and South, but data were not available for adults living in isolated rural areas of the Northeast (Figure 2). This underscores the need to build a more robust infrastructure to investigate COPD in understudied rural areas. We also note that although GOLD guidelines recommend postbronchodilator spirometry to confirm airflow obstruction, the primary analyses used prebronchodilator spirometry to capture the most participant data; post-bronchodilator spirometry was only available for a subset of participants. Multiple large epidemiologic studies have described a strong correlation between preand post-bronchodilator spirometry in predicting outcomes, and lower-limit-of-normal values, which define obstruction according to ATS criteria, are determined using prebronchodilator spirometry (10). Furthermore, a sensitivity analysis that applied the GOLD criteria of FEV1/FVC, 0.70 for individuals with post-bronchodilator spirometry produced results consistent with those obtained in the primary analysis. Lastly, there is a need for individual-level environmental exposure assessments in future studies to better quantify the contribution of factors such as secondhand smoke and heating with solid fuels to disease development in rural areas—a limitation of the present study. Despite these limitations, by using an approach that allowed us to uniquely link multiple nationally representative studies, we confirmed that individuals living in rural areas are at increased risk for spirometry-defined COPD and face greater respiratory morbidity. Further studies are now needed to better understand the risk factors that are unique to rural regions and enable the development of strategies to improve respiratory health and reduce disparities. n