The higher your income, the better your chances of surviving cardiac surgery in both the short and long term, say researchers from Sweden's Karolinska Institutet. Their claim is based on an investigation of medical records from more than 100,000 patients who had undergone cardiac surgery.

Doctors use heart surgery to repair or replace heart valves which control blood flow, repair damaged structures, implant medical devices that control heartbeat, replace a damaged heart with a donor heart, and treat heart failure. The most common type of heart surgery, though, is coronary artery bypass grafting or CABG, according to the National Institutes of Health. During this procedure, a healthy artery or vein is connected to a blocked coronary artery. Heart surgeries frequently save lives, despite its risks.

What, though, is the relationship between income and survival rates following cardiac surgery?

To investigate, a research team led by Dr. Ulrik Sartipy, a cardiac surgeon and associate professor in the department of molecular medicine and surgery, examined the Swedeheart registry for the years 1999 through 2012. The team cross-referenced data from more than 100,000 heart patients with other databases, including that of the National Board of Health and Welfare, which provides information on cause of death, and Statistics Sweden's LISA database, which contains income, level of education, civil status, and other personal details.

Next, the researchers divided all the patients into five equal-sized groups of approximately 20,000 individuals on the basis of household income. Then, they tracked the quintiles for an average of just over seven years. By the end of this period, 29 percent of the patients had died: 43 percent representing the lowest income group and only 14 percent representing the highest.

Certain factors are known to increase post-cardiac surgery death rates: older age, sex (women have a higher risk of dying), kidney disease, diabetes, and suffering from other cardiovascular diseases. To account for the influence of these, the researchers adjusted their figures and discovered the risk of dying after cardiac surgery was about 30 percent lower in the group with the highest income compared to the group with the lowest.

Importantly, the research team did not take into account smoking, diet, physical activity, or adherence to drug regimen following surgery, all of which also affect survival rates, because they lacked the data. The team said these factors, which are also linked to socioeconomic background, might explain the differences in survival rates. Generally, though, people from lower socioeconomic backgrounds are more likely to die at younger ages, the authors explained, which may be due to cardiovascular factors. For this reason, they hope to explore prevention measures targeted at lower-income groups.

Source: Dalén M, Ivert T, Holzmann MJ, Sartipy U. Household Disposable Income and Long-Term Survival After Cardiac SurgeryA Swedish Nationwide Cohort Study in 100,534 Patients. JACC. 2015.