Heart disease, cancer and chronic respiratory disease are the top three leading cause of death in the United States, but a recent study shows that medical errors have caused more deaths than chronic respiratory diseases, claiming the third spot in the rankings.

According to the study published in the journal BMJ, medical errors has claimed more than 250,000 lives in 2013, while 611,105 people died of heart disease, 584,881 died of cancer and 149,205 died of chronic respiratory disease.

Medical errors are oftentimes disregarded in the ranking because it doesn't CDC's way of collecting national health statistics fails to classify medical errors separately on the death certificate, which simply means medical error doesn't appear as the cause of death in patient's death certificate.

Due to the unintentional exclusion of medical errors from the national health statistics, only minimal amount of attention are focused in tackling the causes of medical errors.

"Top-ranked causes of death as reported by the CDC inform our country's research funding and public health priorities," said Martin Makary, M.D., M.P.H., professor of surgery at the Johns Hopkins University School of Medicine and author of the study, in a statement. "Right now, cancer and heart disease get a ton of attention, but since medical errors don't appear on the list, the problem doesn't get the funding and attention it deserves."

For the study, researchers analyzed four separate studies that analyzed medical death rate data from 2000 to 2008, the used hospital admission rates from 2013 to extrapolate total number of hospitalizations and deaths stemmed from medical errors.

Upon crunching all the data, researchers found out that 251,454 out of 35,416,020 hospitalizations resulted to death caused by medical errors, which means 9.5 percent of all deaths in U.S. can be attributed to medical errors.

Medical errors don't necessarily mean that doctors or nurses are inadequate. Most of the errors represent systemic problems, including poorly coordinated care, fragmented insurance networks, the absence or underuse of safety nets, and other protocols.