According to new research published in the CDC’s MMWR, the COPD prevalence in some states is similar for residents regardless of whether they are smokers or nonsmokers.

There is a strong correlation between the state-level incidences of COPD in both nonsmoking and currently smoking populations, indicating that in certain US regions, nonsmoking adults are more likely to be exposed to secondhand smoke, according to a study published in MMWR.

“Cigarette smoking is the leading cause of COPD in the United States,” the researchers wrote. “However, an estimated one-fourth of adults with COPD have never smoked. CDC analyzed state-specific Behavioral Risk Factor Surveillance System data from 2017, which indicated that, overall among US adults, 6.2% (age-adjusted) reported having been told by a healthcare professional that they had COPD.”