CVD Mortality Down But Still Varies Widely Across the US

Pauline Anderson

May 18, 2017

While the overall mortality rate from cardiovascular disease (CVD) has declined by about 50% across the United States in recent decades, extensive variation in related deaths persists between counties, particularly for hypertensive heart disease, ischemic heart disease, and stroke, a new study shows.

Although it's been known for years that there's a wide geographic variation in CVD mortality, "we were surprised at how large the differences were, and we were also surprised at the way that high- and low-risk counties are sometimes right adjacent to each other," lead author, Gregory A. Roth, MD, assistant professor, medicine and cardiology, Institute for Health Metrics and Evaluation, University of Washington, Seattle, told Medscape Medical News.

"Disparities remain a major public health concern, and the federal government, states, counties, and health systems need to be focused on addressing health disparities because they're getting worse."

The study was published online May 16 in JAMA.

The researchers used de-identified death records from the National Center for Health Statistics and information from various other databases. They tabulated deaths and population by county, age group, sex, year, and cause.

For analysis of cause of death, the researchers used a list developed for the Global Burden of Disease study. They believe this is the first county-level analysis of deaths due to conditions other than coronary and cerebrovascular arterial disease, such as diseases of the myocardium, atrial fibrillation (AF), aortic and peripheral artery disease, rheumatic heart disease, and endocarditis.

The researchers applied small area estimation models to obtain mortality rates across the 3110 counties of residence in the United States.

From 1980 to 2014, cardiovascular diseases were the leading cause of death in the United States.

However, the mortality rate from CVD declined from 507.4 deaths per 100,000 persons in 1980 to 252.7 deaths per 100,000 in 2014, which represents a relative decline of 50.2% (95% uncertainty interval, 49.5% - 50.8%).

Nationally, in 2014, ischemic heart disease ranked highest (out of 10 CVD categories) in terms of the mortality rate (155.0 per 100,000 population). The lowest ranked was endocarditis (2.4 per 100,000).

The researchers uncovered large differences in CVD mortality rates between counties. For example, in 2014, hypertensive heart disease mortality was 17.9 deaths per 100,000 for counties at the 90th percentile but 4.3 deaths per 100,000 for counties at the 10th percentile.

There were also large differences between counties at the 90th and 10th percentiles for ischemic heart disease and for cerebrovascular disease.

The county with the highest CVD mortality rate in 2014 was Franklin Parish, Louisiana (545.23), followed by Buffalo County, South Dakota (512.27). The five counties with the lowest CVD morality rates were all in Colorado.

Broad Range

Previous studies have suggested that cardiovascular risk is higher in the southeastern states and lower in the West, and while the new analysis found that pattern to be generally true, it also uncovered other high-risk areas, said Dr Roth.

"Within every state, there is a broad range of risk, so each state contains both high- and low-risk counties. It's not just about these big national trends; it changes over very short distances, so from one freeway exit to the next, you may travel from a high-risk to a low-risk location."

Even within the same city, from one block to the next, there are large variations in risks, said Dr Roth.

The analysis also revealed new patterns of CVD deaths. For example, while the largest concentration of counties with high CVD mortality extended from southeastern Oklahoma along the Mississippi River Valley to eastern Kentucky, several conditions were clustered substantially outside the South. These included AF (Northwest), aortic aneurysm (Midwest), and endocarditis (Mountain West and Alaska).

Researchers also identified "hotspots" of CVD in locations such as Angelina County, Texas (cerebrovascular disease), and northern Michigan (peripheral artery disease).

Previous research has shown a stroke "belt" in the South and a stroke "buckle" across coastal plains of North Carolina, South Carolina, and Georgia, the researchers note. The new analysis showed additional counties with extremely high stroke mortality in California, Utah, North Dakota, South Dakota, and northern Idaho.

Places where CVD deaths are common "are everywhere," noted Dr Roth. "This not simply a problem isolated to just the South or to just to a subset of states."

In contrast to the national trend for CVD mortality rates, mortality rates due to AF, endocarditis, and peripheral artery disease have increased since 1980.

Tracking such trends is important, say the authors, because recommendations for screening and treatment continue to evolve, including rapid adoption of direct oral anticoagulants for AF, less frequent antibiotic prophylaxis to prevent endocarditis, and more percutaneous revascularization for peripheral artery disease.

Contributing Factors

Although the paper didn't address the reasons behind the geographic disparities, Dr Roth said there are likely many contributors, including smoking status, dietary habits, and exercise levels, some of which can affect cholesterol and blood pressure levels, as well as diabetes rates.

"Cardiovascular disease is preventable, which makes the disparities especially concerning," he said.

As well, he added, access to high-quality healthcare might affect CVD mortality rates.

"It's not true that within a city or county everyone has access to the same kind of healthcare or that everyone in general has an opportunity to follow a heart-healthy lifestyle."

Although no single explanation drives the variation in CVD mortality, poverty likely plays a role, Dr Roth speculated.

"What we now need to do is organize the information, the data, that's out there, so we can provide a prescription to counties and communities and tell them not only that they're at high risk but what are the leading factors. And that's something we are already working on," he said.

Researchers also want to "take away lessons" from those areas with the lowest CVD risks, added Dr Roth.

A limitation of the study was that researchers used vital statistics data and census population data to calculate mortality rates. Both of these sources are subject to error because deaths and individuals within the population may be missed or allocated to the wrong county.

Compelling Explanation

Authors of an accompanying editorial agree that variation in social determinants, such as poverty, education, occupation, lifestyle behaviors (diet, physical activity, tobacco and alcohol use, substance abuse), housing quality, and access to good-quality healthcare, are a "compelling explanation" for much of the variation in CVD death rates.

In the commentary, George A. Mensah, MD, Center for Translation Research and Implementation Science, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, and colleagues, note that safe and effective interventions are available for the prevention, treatment, and control of hypertension and that the mortality benefit of intensive blood pressure control in patients at high CVD risk has been demonstrated.

"Nevertheless, nonadherence with antihypertensive medication, a lack of taking actions to control blood pressure, and preventable hospitalizations for hypertension remain high in many of these counties, especially in southeast Oklahoma, northern Texas, northern Louisiana, and the Appalachian Mountain areas of Tennessee, Kentucky, and West Virginia."

The findings of marked geographic disparities in CVD mortality "serve as a critical reminder to challenge clinicians, investigators, and public health leaders to imagine a future in which an individual's risk of cardiovascular death is no longer determined by 'the place' he or she was born or resides and no longer prevents pursuing a healthy and fulfilling life" the editorialists write.

The wide variation in CVD mortality rates provides "a useful target" for developing innovative initiatives that enable communities to "race to the top" in achieving optimum cardiovascular health, they conclude.

"It is anticipated that novel solution discovery will involve collaborative, multilevel, multisector interventions that involve a systems approach to addressing health disparities."

This work was funded by grants from the Robert Wood Johnson Foundation, the National Institute on Aging, and a philanthropic gift from John W. Stanton and Theresa E. Gillespie. Dr Roth reports receiving funding from the Bill and Melinda Gates Foundation. Dr Mensah reports serving a 3-year term as a member of the Global Burden of Disease Scientific Council. This activity is part of his official duties at the National Institutes of Health/National Heart, Lung, and Blood Institute, and he receives no compensation or reimbursement from the Global Burden of Disease Scientific Council or its parent organization, the University of Washington.No other disclosures were reported.

JAMA. Published online May 16, 2017. Abstract, Editorial

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