Average life expectancy in the United States is actually rising more slowly than in other parts of the developed world and the culprit may be chronic conditions. As people live longer, thanks in part to improvements to acute care, they become more likely to develop chronic conditions such as heart disease or cancer.

This means that further breakthroughs in life expectancy may depend on finding new ways to combat chronic conditions. According to a new report from John Hopkins, each chronic condition costs a person an average of 1.8 years of life and multiple conditions increase that impact.

This problem is widespread. According to the Centers for Disease Control and Prevention about half of all adults are now living with at least one chronic medical condition and one in four have multiple. The CDC also reports that seven of the top ten causes of death in 2010 were from chronic conditions, that the majority of US healthcare costs are for those associated with chronic diseases, and that heart disease and stroke alone cost the United States over $315 billion in 2010.

Multiple disease states, also known as multimorbidity, often results in polypharmacy, the taking of multiple drugs, which increases the chance for drug-drug, drug-gene or cumulative interactions, as well as adverse drug effects and treatment failures.

“The medical advances that have allowed sick people to live longer may not be able to keep up with the growing burden of chronic disease. It is becoming very clear that preventing the development of additional chronic conditions in the elderly could be the only way to continue to improve life expectancy,” said Eva H. DuGoff, a PhD at John Hopkins. “The growing burden of chronic disease could erase decades of progress. We don’t want to turn around and see that life expectancy gains have stopped or reversed.”