March 22, 2016
6 min read
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US heart disease death rates declining, but more slowly in South

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Mortality rates from heart disease in the United States declined from 1973 to 2010, but the rate of decline was lowest in the South, according to data published in Circulation.

At the beginning of the study period, the counties with the highest death rates from heart disease were concentrated in the Northeast, but at the end, they were concentrated in the South, Michele Casper, PhD, and colleagues reported.

“This is the most comprehensive study to compare county-level patterns of geographic disparities in heart disease death rates over an extended timeframe,” Casper, epidemiologist at the CDC’s Division for Heart Disease and Stroke Prevention, said in a press release. “These findings provide local communities with important historical context regarding their current burden of heart disease, and emphasize the importance of local conditions in heart disease prevention and treatment efforts.”

Casper and colleagues calculated age-adjusted and spatially smoothed death rates from heart disease in adults aged 35 years or older by county for 2-year intervals from 1973-1974 to 2009-2010. They used a Bayesian spatiotemporal model to calculate precise rate estimates in all counties, even the smallest ones.

Geographic shift

In 1973-1974, the highest tier of age-adjusted heart disease mortality, 974.6 to 1,306 per 100,000 people, “formed an arc stretching from the Northeast through much of Appalachia and into the Midwest,” Casper and colleagues wrote. However, in 2009-2010, the highest tier had a rate of 450 to 769.1 per 100,000 people and “the strong concentration of high-rate counties in the Northeast had dissipated, and a large concentration of high-rate counties emerged in the South and southern Appalachia,” they wrote.

They noted that the counties with the lowest rates of death from heart disease were concentrated in the West in both periods.

The North had 48% of the counties in the highest quintile of heart disease mortality in 1973-1974 but just 4% in 2009-2010, and the Midwest had 17% in 1973-1974 but 6% in 2009-2010, whereas the South had 24% in 1973-1974 and 38% in 2009-2010, Casper and colleagues wrote.

The decline in heart disease mortality rates between 1973-1974 and 2009-2010 ranged by county from 9.2% to 83.4% (average, 61.6%). In the quintile with the slowest declines (9.2% to 49.6%) were primarily counties from Alabama, Mississippi, Louisiana, Arkansas, Oklahoma and parts of Texas, according to the researchers.

The magnitude of geographic inequality for heart disease mortality rates doubled between 1973-1974 and 2009-2010, with the coefficient of variation increasing 3.62% each year on average, they wrote.

The results “suggest that systematic changes may have occurred in a variety of biomedical, behavioral and socioenvironmental factors,” Casper and colleagues wrote.

Race , education could play role

In a related editorial, Donald A. Barr, MD, PhD, from the Program in Human Biology, Stanford Health Care, wrote that previous research showing that “the longitudinal shifts in rates of CHD and HF suggest that black Americans are increasingly bearing the burden of heart disease” could be a factor in the present findings.

Lower rates of smoking and cholesterol levels combined with higher rates of diabetes, obesity and high BP indicate that HF is making a large impact on heart disease mortality, and “this shift disproportionately impacts blacks and others with lower levels of education, population groups found disproportionately in southern states,” Barr wrote.

“As physicians, we need to be able to incorporate [rigorous biosocial training] into our own practice, while also assuring that future physicians will gain this understanding as part of their medical education,” he concluded. – by Erik Swain

Disclosure: The researchers report no relevant financial disclosures. Barr reports receiving royalties from Johns Hopkins University Press for writing three textbooks related to this issue.