Mortality involving breast cancer and chronic lower respiratory diseases among postmenopausal women in the United States: A CDC WONDER analysis (1999–2020).

e13785 Background: Breast cancer and chronic lower respiratory diseases (CLRD) are leading causes of mortality among postmenopausal women in the United States and frequently coexist due to shared risk factors such as aging and multimorbidity. Despite being leading causes of mortality, national trends and population-level disparities in deaths involving both conditions remain underexplored. Methods: We analyzed CDC WONDER data from 1999 to 2020 to assess mortality among postmenopausal women (≥55 years) with breast cancer and CLRD listed as multiple causes of death. Age-adjusted mortality rates (AAMRs) per 100,000 population were calculated using the 2000 U.S. standard population. Trends were stratified by age, race/ethnicity, census region, state, and urbanization status, and evaluated using Joinpoint regression to estimate annual percent change (APC) with 95% confidence intervals. Results: From 1999 to 2020, a total of 51,726 deaths involved co-listed breast cancer and CLRD. Overall AAMRs declined from 1999 to 2017 (APC: −0.80; p < 0.001) but rose sharply from 2017 to 2020 (APC: 4.41; p < 0.001). Non-Hispanic Black women experienced a sustained increase (APC: 1.40; p = 0.0004), while Non-Hispanic White women showed declines until 2018, followed by a reversal. Women aged ≥75 years had the highest mortality and largest recent increase. Regionally, the South showed a consistent upward trend post-2017, with state-level AAMRs ranging from highest in West Virginia to lowest in Utah. Metropolitan areas accounted for higher absolute deaths, whereas non-metropolitan areas exhibited persistently rising rates over time. Conclusions: Breast cancer and CLRD mortality rates among postmenopausal women declined for nearly two decades rising after 2017, with significant disparities by race, geography, urbanization and age. Higher mortality persisted among Non-Hispanic Black women, older adults, and rural populations emphasizes structural inequities and vulnerability to healthcare disruptions. Focused public health interventions addressing multimorbidity and access to care are essential to reduce mortality in high risk populations. Joinpoint APC in age-adjusted mortality, US subgroups (1999–2020). Variable Duration APC Lower 95% CI Upper 95% CI p-value Overall 1999–2017 -0.8 -1.02 -0.58 <0.01 Northeast 1999–2018 -1.52 -2.19 -1.13 0.01 Midwest 1999–2018 -1.04 -3.06 -0.23 0.04 South 2017–2020 6.45 1.12 12.32 <0.01 West 1999–2018 -1.49 -4.87 3.67 0.07 Age 55–74 1999–2017 -1.47 -1.98 -1.2 <0.01 Age 75+ 2006–2017 -1 -3.72 -0.57 <0.01 Metropolitan 1999–2017 -1.03 -1.23 -0.83 <0.01 Black or African American 1999–2020 1.4 0.76 2.25 <0.01 White 1999–2018 -0.53 -0.8 -0.32 <0.01