Geographic Disparities in Declining Rates of Heart Disease Mortality in the Southern United States, 1973–2010

Final published version: http://dx.doi.org/10.5888/pcd11.140203 Copyright information: Conditions for Use of CDC Text and Materials General text information, publications available for download, and graphs developed by CDC and presented on CDC's website are works of the United States Government and are in the public domain. This means that they are meant for public use and are not subject to copyright law protections. Permission is not required for use of public domain items.


Background
In the United States, heart disease mortality has decreased since the 1950s (1). However, these declines have not occurred uniformly across the country, and slower rates of decline may indicate increased need for heart disease prevention policies and programs (2). In this article, we document the geographic inequalities in declining heart disease death rates in the South -a region with high heart disease mortality rates. We also consider methods for generating county-level estimates of changing heart disease death rates.

Methods
Our analysis was limited to 1,420 counties in the South US Census Region. The annual number of county-level heart disease deaths from 1973 to 2010 among people aged 35 years or older was obtained from the National Center for Health Statistics (NCHS). Heart disease deaths were defined according to the following International Classification of Diseases (ICD) codes: ICD-8: 390-398, 402, 404, 410-429; ICD-9: 390-398, 402, 404-429; ICD-10: I00-I09, I11, I13, I20-I51. County-level population estimates were also obtained from the NCHS Centers for Disease Control and Prevention (CDC) WONDER database. These data were sequentially 1) aggregated into 2-year intervals, 2) age-standardized (using the 2000 US standard population), and 3) spatially smoothed using Bayesian methods, with the first and third steps enhancing rate stability of counties with small populations (3). Only counties with 2-year populations greater than 1,000 at all intervals were included.
These stabilized, age-standardized, biennial county-level heart disease death rates were modeled using a spatially independent Poisson generalized linear mixed model with a fixed intercept and temporal slope and county-level random intercept and temporal slope using SAS version 9. www.cdc.gov/pcd/issues/2014/14_0203.htm • Centers for Disease Control and Prevention this model, county-level temporal changes (ie, percentage declines) in heart disease death rates were summarized as the exponentiated linear combination of the fixed and random slopes. The resulting county-level percentage declines in heart disease death rates  were mapped (ArcMap, ESRI), with categories defined according to the mean and standard deviation.

Main Findings
This map illustrates substantial geographic disparities in declining heart disease death rates in the South from 1973 to 2010. Although the mean county-level percentage decline in heart disease mortality was 49.9% (standard deviation, 11.1%), the magnitude of change varied among counties from a decline of 79.9% to an increase of 2.8%. The largest declines were concentrated in central and west Texas and the Atlantic Coast, and the smallest declines were observed in counties along the Mississippi River, eastern Kentucky, and parts of Oklahoma and Alabama.

Action
This map illustrates impressive reductions in heart disease mortality in most counties in the South during the past 40 years. By employing statistical models widely used in public health, we have summarized multiple years of data into a single, readily interpretable value, enabling greater understanding of the geographic variation in declining heart disease mortality. The wide range and geographic patterning of declining heart disease death rates in the South reinforces the importance of place on the population burden of heart disease (5). Areas with slower rates of decline, including parts of the Mississippi Delta, Kentucky, Oklahoma, and Alabama, suggest the need for enhanced heart disease prevention efforts. Future research is needed to better understand the observed spatial variation in declining heart disease mortality, including exploration of disparities in declines by race, sex, and social context.