Trends in heart failure-related cardiovascular mortality in rural versus urban United States counties, 2011-2018: A cross-sectional study

Abstract

Background: Adults in rural counties in the United States (US) experience higher rates broadly of cardiovascular disease (CVD) compared with adults in urban counties. Mortality rates specifically due to heart failure (HF) have increased since 2011, but estimates of heterogeneity at the county-level in HF-related mortality have not been produced. The objectives of this study were 1) to quantify nationwide trends by rural-urban designation and 2) examine county-level factors associated with rural-urban differences in HF-related mortality rates.

Methods and findings: We queried CDC WONDER to identify HF deaths between 2011-2018 defined as CVD (I00-78) as the underlying cause of death and HF (I50) as a contributing cause of death. First, we calculated national age-adjusted mortality rates (AAMR) and examined trends stratified by rural-urban status (defined using 2013 NCHS Urban-Rural Classification Scheme), age (35-64 and 65-84 years), and race-sex subgroups per year. Second, we combined all deaths from 2011-2018 and estimated incidence rate ratios (IRR) in HF-related mortality for rural versus urban counties using multivariable negative binomial regression models with adjustment for demographic and socioeconomic characteristics, risk factor prevalence, and physician density. Between 2011-2018, 162,314 and 580,305 HF-related deaths occurred in rural and urban counties, respectively. AAMRs were consistently higher for residents in rural compared with urban counties (73.2 [95% CI: 72.2-74.2] vs. 57.2 [56.8-57.6] in 2018, respectively). The highest AAMR was observed in rural Black men (131.1 [123.3-138.9] in 2018) with greatest increases in HF-related mortality in those 35-64 years (+6.1%/year). The rural-urban IRR persisted among both younger (1.10 [1.04-1.16]) and older adults (1.04 [1.02-1.07]) after adjustment for county-level factors. Main limitations included lack of individual-level data and county dropout due to low event rates (<20).

Conclusions: Differences in county-level factors may account for a significant amount of the observed variation in HF-related mortality between rural and urban counties. Efforts to reduce the rural-urban disparity in HF-related mortality rates will likely require diverse public health and clinical interventions targeting the underlying causes of this disparity.

Fig 1. Annual nationwide heart failure-related mortality rates stratified by age and rural-urban status, Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research 2011–2018.

Heart failure mortality in the United States between 2011–2018 according to rural-urban status among adult age (A) 35–64 years and (B) 65–84 years. Rural-urban status determined based on the 2013 NCHS Urban-Rural Classification Scheme for Counties. AAMR expressed as number of deaths per 100,000 population. AAMR = age-adjusted mortality rate.

Fig 2. County-level heart failure-related age-adjusted mortality rates in the United States, Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research 2011–2018.

Counties were grouped according to their quintile of HF AAMR using pooled HF events between 2011 through 2018. Black and White decedents ages 35–84 were included. Counties censored for confidentiality purposes or counties with an AAMR reported as “unreliable” by CDC WONDER (<20 events) were excluded. AAMR = Age-adjusted mortality rate. Basemap Sources: Esri, TomTom North America, Inc., U.S. Census Bureau, U.S. Department of Agriculture (USDA), National Agricultural Statistics Service (NASS).

Fig 3. Contributions of aggregate county-level factors to the rural heart failure-related mortality penalty.

Forest plots for negative binomial regression models of rural status and HF-related mortality adjusted for groups of county-level factors. *Adjusted demographic factors including percent of residents over age 65 years, percent of female residents, percent of non-Hispanic Black residents, and percent of Hispanic residents according to the US Census Bureau 2011 Population and Housing Unit Estimates. †Adjusted for socioeconomic factors including percent of residents in poverty, percent of residents unemployed, percent of residents uninsured age 18–64, and median household income according to the US Census Bureau 2011 Small Area Income and Poverty Estimates Program and Small Area Health Insurance Estimates Program. ‡Adjusted for clinical characteristics of residents including percent of residents with diabetes and percent of residents with obesity from the Centers for Disease Control and Prevention 2011 Behavioral Risk Factor Surveillance System. §Adjusted for clinician density including number of primary care physicians and number of cardiologists per 100,000 residents according to the Health Resources and Services Administration Area Health Resources File (primary care physician density from 2011 and cardiologist density from 2010). | |Adjusted for all covariates in models 2–5.

Fig 4. Associations between county-level factors and age-adjusted heart failure-related mortality rates stratified by rural-urban status and age, Centers for Disease Control and Prevention Wide-Ranging Online Data for Epidemiologic Research 2011–2018.

IRRs for HF-related mortality between quintiles of individual county-level factors in fully-adjusted model relative to lowest quintile. Results are representative of four fully-adjusted negative binomial regression models for age (35-64y and 65-84y) and rural-urban subgroups. Data sources as in Fig 3. HF = heart failure; IRR = incidence rate ratio; PCP = primary care physician; y = year.