Trends in the Prevalence of Chronic Obstructive Pulmonary Disease Among Adults Aged ≥18 Years — United States, 2011–2021

Chronic obstructive pulmonary disease (COPD) is a leading cause of death in the United States. Overall COPD prevalence declined during 1999-2011. Trends in COPD prevalence during the previous decade have not been reported. CDC analyzed 2011-2021 Behavioral Risk Factor Surveillance System data to assess trends and differences in self-reported physician-diagnosed COPD prevalence among U.S. adults aged ≥18 years. Age-standardized prevalence of COPD did not change significantly from 2011 (6.1%) to 2021 (6.0%). Prevalence was stable for most states and subgroups; however, it decreased significantly among adults aged 18-44 years (average annual percent change [AAPC] = -2.0%) and increased significantly among those aged ≥75 years (AAPC = 1.3%), those living in micropolitan counties (0.8%), and among current (1.5%) or former (1.2%) smokers. COPD prevalence remained elevated in the following groups: women, adults aged ≥65 years, those with a lower education level, unable to work, living in rural areas, and who ever smoked. Evidence-based strategies, especially those tailored for adults disproportionately affected, can reduce COPD prevalence, and address the continued need for prevention, early diagnosis, treatment, and management.


Introduction
Chronic obstructive pulmonary disease (COPD) is a group of progressive lung diseases, including emphysema and chronic bronchitis.COPD accounts for most of the deaths from chronic lower respiratory diseases, the sixth leading cause of death in the United States in 2021 (1).Elevated prevalence of COPD has been reported in the following groups: women, older adults (aged ≥65 years), residents in rural areas, adults with a lower education level, and those who ever smoked (2).During 1999-2011, estimates from the National Health Interview Survey (NHIS) indicated that the prevalence of self-reported physician-diagnosed COPD significantly declined among U.S. adults (aged ≥25 years) overall and among adults aged 25-44 years (3).Trends and differences in COPD prevalence during the previous decade have not been reported overall and by subgroups.

Data Collection
The Behavioral Risk Factor Surveillance System (BRFSS) is an annual state-based, random-digit-dialed mobile and landline telephone survey among noninstitutionalized U.S. adults aged ≥18 years; the survey covers all 50 states, the District of and by state.Overall and for all subgroups, linear and nonlinear trends in COPD prevalence during 2011-2021 were assessed using permutation tests in Joinpoint trend analysis software (version 4.8.0.1;National Cancer Institute § § ).Annual percent change (APC) for each line segment (when joinpoints were identified) and average annual percent change (AAPC) from 2011 to 2021 were estimated.Differences by selected characteristics (compared with a reference category) in COPD prevalence for years 2011 and 2021 were assessed using t-tests.Linear trend tests were performed using orthogonal polynomial contrasts for ordinal variables.¶ ¶ The statistical significance level for all the tests was set at alpha = 0.05.Analyses were conducted using SAS software (version 9.4; SAS Institute) and SAS-callable SUDAAN software (version 11.0.1;RTI International) to account for the complex sample design and weighting.This activity was reviewed by CDC, deemed not research, and was conducted consistent with applicable federal law and CDC policy.***

Differences by Sociodemographic Characteristics
An estimated 6.4% of U.S. adults (population estimate = 14.3 million) in 2011 and 6.5% (14.2 million) in 2021 had COPD (Table 1   ).Florida was unable to collect data during enough months to meet the minimum requirements for inclusion in the 2021 public-use dataset.† Indicates a nonlinear trend if the number of joinpoints is equal to one or more.§ Dashes indicate that no joinpoints (no line segments) were identified using permutation test in the best-fit joinpoint model.¶ Age-standardized COPD prevalence was calculated using the 2000 U.S. Census Bureau projected U.S. adult population with five age groups (18-24, 25-34, 35-44, 45-64, and ≥65 years) Distribution #9.https://www.cdc.gov/nchs/data/statnt/statnt20.pdf** Indicates statistically significant difference on the basis of t-tests in the COPD prevalence between the reported level of each characteristic and the Ref (p<0.05).
prevalence was higher among women than among men, higher among non-Hispanic American Indian or Alaska Native and non-Hispanic other persons than among non-Hispanic White persons, higher among persons who were unemployed, retired, homemakers or students, and unable to work than among those who were employed, and higher among adults who were current or former smokers than among never smokers; prevalence was lower among non-Hispanic Asian, Native Hawaiian, Pacific Islander, or Hispanic persons than among non-Hispanic White persons.COPD prevalence increased with increasing age, decreasing education level, and decreasing urbanicity.

Discussion
An estimated 14.2 million (6.5%)U.S. adults had physiciandiagnosed COPD in 2021.Overall prevalence remained unchanged since 2011.These results are consistent with overall COPD mortality rates, which remained unchanged during 1999−2019 (4).The prevalence of COPD among adults aged <45 years declined from 2011 to 2021, consistent with the trend during 1999-2011 (3).One reason might be the more pronounced decline in prevalence of current smoking among adults aged 18-44 years (36.4% relative decline) than among those aged 45-64 years (22.6%) and those aged ≥65 years (2.1%) from 2005 to 2015 (5); cigarette smoking is the dominant cause of COPD among U.S. adults.† † † Explanations for the higher prevalence in COPD among those living in micropolitan and noncore counties might include the persistently high prevalence of smoking among adults in rural areas (6), the lower rates of persons quitting smoking (7), and the increasing proportion of older adults living in rural areas.§ § § The variation in the prevalence of COPD by states is likely related to factors including differences in smoking rates, occupations or industries with higher risk for COPD, and access to health care for screening and detection of COPD (8,9).Approximately 25% of adults with COPD (3.8 million) reported having never smoked, similar to 1988-1994 (10).In addition to cigarette smoking, secondhand smoke and occupational and environmental exposures are also risk factors for developing COPD among nonsmokers (8).Therefore, promotion of smoke-free environments ¶ ¶ ¶ and workplace interventions (e.g., raising awareness of harmful work-related respiratory exposures, elimination or substitution of hazardous exposures, and improving ventilation) can help reduce or eliminate COPD-related risk factors.****¶ ¶ ¶ https://www.cdc.gov/tobacco/secondhand-smoke/index.html**** https://www.sciencedirect.com/science/article/pii/S2213260021005063? via%3Dihub

Limitations
The findings in this report are subject to at least four limitations.First, the diagnosis of COPD, sociodemographic characteristics, and smoking status are all self-reported, and might be subject to recall and social desirability bias.Second, potential systematic bias resulting from low response rates might affect the results.The flat overall trend is also observed in the 2014-2018 NHIS, † † † † suggesting that nonresponse bias did not significantly affect the conclusions of this report.Third, because there were no differences in COPD prevalence in 2020 or 2021 relative to 2019, it appears unlikely that the COVID-19 pandemic influenced reporting of physician-diagnosed COPD.Finally, the findings might not be extrapolated to adults in long-term † † † † https://www.lung.org/research/trends-in-lung-disease/copd-trends-brief/copd-prevalence ).In 2011 and 2021, age-standardized COPD § § https://surveillance.cancer.gov/joinpoint/ ¶ ¶ https://www.cdc.gov/nchs/data/series/sr_02/sr02_179.pdf*** 45 C.F.R. part 46.102(l)(2), 21 C.F.R. part 56; 42 U.S.C.Sect.241(d); 5 U.S.C.Sect.552a; 44 U.S.C.Sect.3501 et seq.