Lung Cancer Incidence in Nonmetropolitan and Metropolitan Counties — United States, 2007–2016

Mary Elizabeth O'Neil, MPH; S. Jane Henley, MSPH; Elizabeth A. Rohan, PhD; Taylor D. Ellington, MPH; M. Shayne Gallaway, PhD

Disclosures

Morbidity and Mortality Weekly Report. 2019;68(44):993-998. 

In This Article

Abstract and Introduction

Introduction

Lung and bronchus (lung) cancer is the leading cause of cancer death in the United States.[1] In 2016, 148,869 lung cancer deaths were reported.* Most lung cancers can be attributed to modifiable exposures, such as tobacco use, secondhand smoke, radon, and asbestos.[1] Exposure to lung cancer risk factors vary over time and by characteristics such as sex, age, and nonmetropolitan or metropolitan residence that might affect lung cancer rates.[1,2] A recent report found that lung cancer incidence rates were higher and decreased more slowly in nonmetropolitan counties than in metropolitan counties.[3] To examine whether lung cancer incidence trends among nonmetropolitan and metropolitan counties differed by age and sex, CDC analyzed data from U.S. Cancer Statistics during 2007–2016, the most recent years for which data are available. During the 10-year study period, lung cancer incidence rates were stable among females aged <35, 45–64, and ≥75 years in nonmetropolitan counties, were stable among females aged <35 years in metropolitan counties, and decreased in all other groups. Overall, among males, lung cancer incidence rates decreased from 99 to 82 per 100,000 in nonmetropolitan areas and from 83 to 63 in metropolitan areas; among females, lung cancer incidence rates decreased from 61 to 58 in nonmetropolitan areas and from 57 to 50 in metropolitan areas. A comprehensive approach to lung cancer prevention and control includes such population-based strategies as screening for tobacco dependence, promoting tobacco cessation, implementing comprehensive smoke-free laws, testing all homes for radon and using proven methods to lower high radon levels, and reducing exposure to lung carcinogens such as asbestos.[1] Increasing the implementation of these strategies, particularly among persons living in nonmetropolitan counties, might help to reduce disparities in the decline of lung cancer incidence.

Data on new cases of invasive lung cancers diagnosed during 2007–2016 were obtained from U.S. Cancer Statistics. During this 10-year period, data from all registries met data quality criteria,§ but county-level data were not available for Kansas and Minnesota; therefore, data in this report cover approximately 97% of the U.S. population. The U.S. Department of Agriculture Economic Research Service 2013 vintage rural-urban continuum classification scheme was used to categorize county of residence at diagnosis as nonmetropolitan (rural-urban continuum codes 4–9) or metropolitan (rural-urban continuum codes 1–3).

Calculation of annual incidence rates per 100,000 persons used modified annual population estimates in the denominator and was age-adjusted by the direct method to the 2000 U.S. standard population.** Rates were examined by sex, age group, and nonmetropolitan or metropolitan county status. Rate ratios were calculated to test whether sex-, age- and year-specific rates in nonmetropolitan counties differed from those in metropolitan counties; rates were considered significantly different (p<0.05) if the 95% confidence interval (CI) for the rate ratio excluded one. Annual percentage change (APC) was used to quantify the change in incidence over time and was calculated using least-squares regression. A two-sided t-test was used to determine whether APC was significantly different from zero. Rates were considered to increase if APC >0 (p<0.05) and to decrease if APC <0 (p<0.05); otherwise rates were considered stable. Absolute change was calculated as the difference in incidence from 2007 to 2016. To allow for informal comparisons, without specifying a referent group, 95% CIs for rates and APCs are presented. Analyses were performed using SEER*Stat software (version 8.3.6; National Cancer Institute).

From 2007 to 2016, lung cancer incidence rates declined in both nonmetropolitan and metropolitan counties among both males and females, but the rate of decline differed by sex and rural-urban status. In 2007, lung cancer incidence rates among males in nonmetropolitan counties (99 per 100,000) were 60% higher than that among females in nonmetropolitan counties (61 per 100,000); in 2016, the rate among males (82 per 100,000) in nonmetropolitan counties was 40% higher than that of females in nonmetropolitan counties (58 per 100,000) (Figure 1).

Figure 1.

Trends* in lung cancer incidence rates in nonmetropolitan and metropolitan counties,§ by sex — United States, 2007–2016
Abbreviation: APC = annual percentage change.
*Trends were measured with APC in rates; all APCs were significantly different from zero (p<0.05).
Per 100,000 persons and age-adjusted to the 2000 U.S. standard population.
§The U.S. Department of Agriculture Economic Research Service 2013 vintage rural-urban continuum codes were used to categorize county residence at time of cancer diagnosis as nonmetropolitan (codes 4–9) or metropolitan (codes 1–3). https://www.ers.usda.gov/data-products/rural-urban-continuum-codes.
Cancer incidence data were compiled from 49 cancer registries that meet the data quality criteria for all invasive cancer sites combined, representing approximately 97% of the U.S. population. (County-level data were not available for Kansas and Minnesota.)

In metropolitan areas, incidence rates declined more sharply among both males (APC = −2.9%) and females (−1.5%) than it did among males (−2.1%) and females (−0.5%) in nonmetropolitan areas (Figure 1). Lung cancer incidence rates decreased among males in all age groups in both nonmetropolitan and metropolitan counties. Among males, the largest declines were among those aged 45–54 years in metropolitan counties (APC = −5.2%) and those aged 35–44 years in nonmetropolitan counties (APC = −5.0%) (Table). Lung cancer incidence rates also decreased among females in metropolitan counties for most age groups, except those aged <35 years; the largest decline was among females aged 35–44 years in metropolitan counties (APC = −5.0%). Among females in nonmetropolitan counties, incidence rates declined among those aged 35–44 years (APC = −3.6%) and 65–74 years (APC = −1.3%) and were stable in all other age groups (Table).

In 2016, among persons aged ≥55 years, the highest lung cancer incidence rates were observed among men in nonmetropolitan counties (Figure 2). Among persons aged 35–54 years, rates in nonmetropolitan and metropolitan counties did not differ by sex but were higher in nonmetropolitan counties than in metropolitan counties. Rates were higher among women aged 35–64 years in nonmetropolitan counties than among men in metropolitan counties (Figure 2).

Figure 2.

Rate* of lung cancer in nonmetropolitan and metropolitan counties, by sex and age at diagnosis — United States 2016
*Per 100,000 persons and age-adjusted to the 2000 U.S. standard population.
The U.S. Department of Agriculture Economic Research Service 2013 vintage rural-urban continuum codes were used to categorize county residence at time of cancer diagnosis as nonmetropolitan (codes 4–9) or metropolitan (codes 1–3). https://www.ers.usda.gov/data-products/rural-urban-continuum-codes.
§Cancer incidence data were compiled from 49 cancer registries that meet the data quality criteria for all invasive cancer sites combined, representing approximately 97% of the U.S. population. (County-level data were not available for Kansas and Minnesota.)

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