Post-Discharge Factors Could Explain Why Poor Heart Disease Patients Have Worse Outcomes
DURHAM, NC -- A Duke University Medical Center analysis of the relationship between income and heart disease has shown that poverty is associated with worse short- and intermediate-term outcomes -- despite the fact that low- and high-income patients generally receive similar levels of care while in the hospital.
This finding leads researchers to conclude that post-discharge factors, rather than in-hospital care, could explain the differences in outcomes. Such factors include poor diet, a higher likelihood of smoking, non-compliance with medications and an inability to afford medications.
The researchers said that their analysis was based on actual household income data, unlike past observational studies that have used such "proxies" as education levels or the median income for their ZIP code. The patients Duke studied showed that when compared to high-income patients, those with family incomes below $20,000 a year tended to be older, female, African-American and less educated. Low-income patients also tended to have higher rates of diabetes, high blood pressure and prior heart procedures.
"We are dealing with a rapidly aging population requiring increasing levels of care for heart disease, and we as physicians are obligated to treat everyone the same," said Sunil Rao, MD, fellow at the Duke Clinical Research Institute. The results of the Duke analysis were published today (June 4, 2003) in the Journal of the American College of Cardiology. "As a society, we have an obligation to help patients be able to afford and take their medications."
For their analysis, the Duke researchers mined the data gathered from the economic substudy of the much larger PURSUIT (Platelet Glycoprotein IIb/IIIa in Unstable Angina: Receptor Suppression Using Integrilin Therapy) trial, which enrolled 10,928 patients in a study of a new drug to prevent blood clots from forming in heart attack patients. Of that group of patients, 2,207 completed a questionnaire about their economic status.
"This was the first time that this type of information was collected in an American clinical trial in cardiology," Rao said. "Since everyone enrolled in a specific clinical trial receives the same standardized care while in the hospital, this set of data gave us a unique opportunity to look at these economic issues without being clouded by other factors."
In their analysis, the researchers divided the patients into three groups: 1,000 low-income patients with annual household incomes less than $20,000; 952 middle-income patients with annual household incomes between $20,000 and $60,000; and 255 high-income patients with annual household income greater than $60,000. The researchers then examined how all the patients fared after 30 days and six months after being discharged from the hospital.
After 30 days, 14.2 percent of low-income patients had died or had another heart attack, compared to 12.9 percent in the middle-income group and 9 percent for the high-income group. After six months, 18.8 percent of the low-income group had died or suffered another heart attack, compared to 15.7 percent for the middle-income group and 11.4 percent of the high-income group.
In terms of the treatment received while in the hospital, low-income patients were less likely to receive lipid-lowering agents, but were more likely to receive ACE inhibitors when compared to high-income patients. Lower income levels were associated with lower use of cardiac catheterization and angioplasty, but higher rates of coronary artery bypass surgery.
"However, when we controlled for the baseline differences between the income groups, the trend toward worse outcomes persisted for the low-income patients, but the differences were no longer statistically significant," Rao explained. "Also, the six-month outcomes were worse for low-income patients than the 30-day outcomes, when compared to the high-income patients."
Since the in-hospital care received by the patients was similar, the trend toward worse outcomes could be explained by specific patient or environmental factors. Previous studies have shown that lower income people tend to smoke more and exercise less, and they also tend to have such heart disease risk factors as high cholesterol and blood pressure, said the researchers.
"The poor are intuitively less able to afford medications prescribed for them at discharge from the hospital," Rao continued. "Although many insurance policies provide coverage for prescription drugs, a greater proportion of the low-income patients were covered by Medicare, which currently doesn't provide a prescription drug benefit."
The findings raise important health care policy issues, Rao said, since most of the very poor tend to be elderly. In the current analysis, the average age of the low-income group was 65, compared to 61 in the middle-income group and 56 in the high-income group.
"The elderly, whose numbers continue to grow, are those who are the most impacted by heart disease," Rao continued. "They keep coming to the hospital with heart problems, which we treat and then send them home on medications they may have trouble affording."
The PURSUIT trial was funded by Millennium Pharmaceuticals, Cambridge, MA, and Key-Schering-Plough, Kenilworth, NJ. Rao's analysis was funded by the DCRI.
Other Duke members of the team were: Padma Kaul, PhD, Kristin Newby, MD, Robert Harrington, MD, Daniel Mark, MD and Eric Peterson, MD. Also part of the team were A. Michael Lincoff, MD, Cleveland Clinic Foundation, and Judith Hochman, St. Luke's-Roosevelt Medical Center, New York.