CVD Hospitalization in Older Adults Higher in US Than in Denmark

Americans are much more likely to be hospitalized for a cardiovascular event, particularly MI and heart failure (HF), than those from Denmark, another high-income country with a distinctly different healthcare system.

The international comparison provides important public health insights into the burden of cardiovascular disease, with investigators saying the higher hospitalization rate in the US is likely attributable to multiple factors.

Regardless of the reasons, senior researcher Rishi Wadhera, MD (Beth Israel Deaconess Medical Center, Boston, MA), said, the magnitude of difference took him aback. “Fifty percent higher, or a 1.5-fold higher [rate of hospitalization] in the US, is significant both from a public health standpoint and from an economic standpoint,” he told TCTMD.

The study, which was published this week in JAMA Cardiology, also exposed income-based disparities in hospitalizations in both countries.

“In the US, when you look at low-income versus higher-income adults, the magnitude of the disparity in cardiovascular hospitalizations was much larger than in Denmark,” said Wadhera. “Low-income adults in the US are 2.5 times more likely to be hospitalized for a cardiovascular condition compared with higher-income adults—that’s a huge difference. It feels unacceptable to have these stark disparities in hospitalizations for cardiovascular events in a high-income country like the US.”

Apples-to-Apples Comparison

The US study population included adults 65 years or older captured using Medicare inpatient claims data, while the National Patient Registry was used to identify patients of similar ages in Denmark. The rationale of the study, said Wadhera, was to assess the burden of cardiovascular disease hospitalizations in the US and compare outcomes with another high-income country with a universal healthcare system. The focus on US Medicare data and the Danish registry allowed researchers to capture nearly all adults 65 years or older.

“It’s really an apples-to-apples comparison in terms of age groups,” said Wadhera.

The US population included 58,614,110 adults (mean age 74.6 years; 54.9% female), of whom 2.0% were hospitalized for a cardiovascular event (MI, ischemic stroke, or HF). In Denmark, 1,176,542 patients (mean age 75.3 years; 53.9% female) were included in the analysis, of whom 1.4% were hospitalized for an event.

The overall age- and sex-standardized cardiovascular hospitalization rate was 20.8 per 1,000 persons in the US versus 13.9 per 1,000 persons in Denmark (risk ratio 1.50; 95% CI 1.47-1.52). The difference between countries was largest for HF hospitalizations, with the relative rate more than twofold higher in the US (RR 2.37; 95% CI 2.31-2.43). With MI, the hospitalization rate was also higher in the US than in Denmark (RR 1.56; 95% CI 1.51-1.61), a difference that was largely driven by more hospitalizations for NSTEMI. Hospitalizations for stroke were less common in the US than in Denmark (RR 0.90; 95% CI 0.88-0.93).

It feels unacceptable to have these stark disparities in hospitalizations for cardiovascular events in a high-income country like the US. Rishi Wadhera

The researchers also looked at cardiovascular hospitalizations by income level in each country. In the US, low-income adults—defined as those in the lowest 15th percentile of household income based on the past 3 years of data—were more than twofold more likely to be hospitalized for cardiovascular events than high-income adults (RR 2.38; 95% CI 2.25-2.47).

There was also an income gap seen in Denmark, although it was smaller than in the US. Low-income Danish adults were nearly 1.5 times more likely to be hospitalized for MI, stroke, or HF compared with their high-income counterparts. 

Multiple Reasons for Differences

In terms of what explains the results, Wadhera said there are several hypotheses. For one, the prevalence of cardiometabolic risk factors—hypertension, dyslipidemia, and diabetes—is much higher among older adults in the US compared with older adults in Denmark, and this likely contributes to the higher rates of acute cardiovascular hospitalization. 

Additionally, the healthcare systems are very different, with the US system highly fragmented, which creates barriers to accessing care, including for screening and primary prevention, he said. In Denmark, the universal healthcare system allows free access to people of all ages. 

“It provides access to medical services without direct out-of-pocket costs at the point of care,” said Wadhera. “Contrast that to the United States, where many folks, before they reach the age of 65, rely on commercial insurance plans or are uninsured. They are often responsible for copayments, or different forms of cost-sharing, which we know can be a barrier to accessing important preventative screening services.”

This “crisis of affordability” among the insured and 26 million Americans who lack health insurance likely plays a significant role explaining the different hospitalization rates between countries, he said. 

Finally, there are different social risk factors at play, said Wadhera. While both are high-income countries, Denmark has one of the lowest poverty rates (the US has one of the highest) and also ranks among the best when it comes to income equality. Social determinants of health—access to healthy food, housing stability, and other environmental exposures—are more favorable in Denmark than in the US.

All of the reasons listed, added Wadhera, are related to each other, with none existing in isolation.

In an editor’s note, Sadiya Khan, MD (Northwestern University Feinberg School of Medicine, Chicago, IL), says the comparison with Denmark is apt given their universal healthcare system and greater focus on prevention. She points out that Denmark is roughly the same size as Colorado, and that there are considerable differences in risk factors, morbidity, and mortality seen across state and county lines in the US.

“To change course, and to improve the health of Americans, there needs to be fundamental changes in the national approach to healthcare delivery with a greater focus on public health preventive efforts and health equity,” writes Khan.