Patients with heart failure in the USA are more likely to be hospitalised and more likely to die during the colder winter months, according to two studies presented at the American College of Cardiology’s 66th Annual Scientific Session (ACC; 17-19 March, Washington, DC, USA). One study also shows the costs per hospitalisation for heart failure also increase during winter.
Although studies from Europe, Australia, Asia and elsewhere have shown similar seasonal trends in heart failure hospitalisations and deaths, these studies are the first to look at these trends in the USA. Previous research has also shown that heart attacks, sudden cardiac death and cholesterol levels tend to increase during the winter months in the country.
“Over five and a half million people live with heart failure in the USA, and it is one of the leading causes of hospitalisation. But little to nothing has been known about how seasonal variation impacts hospitalisation outcomes nationally,” says Emmanuel Akintoye, resident physician in internal medicine at Wayne State University/Detroit Medical Center, Detroit, USA, and the lead author of one of the studies. Understanding these patterns can help doctors, hospital administrators and patients plan for and perhaps prevent excess admissions in winter, he says.
Akintoye and his colleagues examined data from approximately 600,000 hospital admissions for heart failure collected between 2011 and 2013 from the Nationwide Inpatient Sample, which includes the health records of patients admitted at more than 1,000 hospitals comprising about 20 percent of US medical centres. They found that the likelihood of dying during hospitalisation for heart failure, as well as the cost and length of that hospitalisation, all spiked during the winter. A patient with heart failure admitted in winter had a 6% higher risk of dying than one admitted in spring, as well as an 11% higher risk of dying than one admitted in summer or autumn. The median cost for heart failure-related hospitalisations in the winter was US$7,459, while for summer it was US$7,181, a statistically significant difference.
Akintoye says that while the study design did not allow them to explore reasons for these upticks in mortality and cost, the increased prevalence of co-morbidities such as respiratory infections in winter, which can exacerbate heart failure symptoms, likely play a role. So do cold temperatures, he added, which can lead to increased heart rate and increased blood pressure, further taxing an already overworked heart.
A second study, led by Soumya Patnaik, internal medicine physician at the Albert Einstein Medical Center in Philadelphia, USA, found similar results. Patnaik and her colleagues looked at data from almost two million hospitalisations for heart failure between 2002 and 2011 from the National Institutes of Health database. In their sample, hospitalisations and deaths from heart failure while in hospital were both highest in winter and lowest in late summer.
The researchers further analysed heart failure hospitalisations by geographical region—the Northeast, Midwest, South and West. Interestingly, in their dataset, the South had the largest number of overall admissions for heart failure, but the Northeast had the highest mortality: 4.3% of admitted patients died, compared to a national average of 3.8%. This risk of death was highest in January and February, even in parts of the country with overall warmer temperatures.
“Based on our findings, it is fair to suggest that heart failure patients should take extreme caution in wintertime—being extra cautious about taking timely medications, not getting exposed to cold [temperatures] if it is not necessary, and being careful about their diet as well, such as limiting salt and not overindulging over the holiday season,” Patnaik says.
Clinicians should also be careful to counsel patients about medication and diet compliance during winter and, if appropriate, implement more frequent follow-up for heart failure patients at high risk of hospitalisation, she says.
Neither research group tracked how patients fared after discharge from the hospital, nor were they able to factor in whether patient hospitalisations were due to acute episodes of heart failure or readmissions.
Currently, the US Centers for Medicare and Medicaid Services penalises hospitals for 30-day readmissions for heart failure.
Researchers say they believe awareness of these trends in heart failure admissions could enable policymakers and health care providers to anticipate the surge of hospitalisations and poorer outcomes during winter and plan ahead, Akintoye says. In addition, he says, if this seasonal variability is well appreciated, that could stimulate research into its causes.
“Once we understand the causes, we can work towards trying to address the problem and increase survival for patients with heart failure,” he says.