Doctors coming up the pipeline had better learn to multitask if they’re ever going to make it in tomorrow’s hospitals. A new study finds more and more Americans are suffering from multiple chronic conditions at once, and their life expectancies — indeed, the entire country’s — hang in the balance.

Researchers from Johns Hopkins Bloomberg School of Public Health wanted to find out what effect multiple conditions have on people’s life expectancy, in particular when people contract more and more. They found that for each additional ailment, people lived an average of 1.8 years fewer; however, the scale isn’t linear. Two conditions wipe out not even a year from your life, but the seventh condition could knock out five or six. According to the World Health Organization, the average American will die right before his 80th birthday.

Eva H. DuGoff, a recent PhD recipient and lead author of the study, says the problem is here to stay. "Living with multiple chronic diseases such as diabetes, kidney disease, and heart failure is now the norm and not the exception in the United States,” she said in a statement.

DuGoff and her colleagues looked at the medical records of 1.4 million people 67 years and older who were enrolled in Medicare as of Jan. 1, 2008. They found the average 75-year-old woman, with no conditions, would go on to live an additional 17.3 years. With five conditions, she would live 12 years; with 10, only five. The type of disease also matters. Heart disease is mild: People can expect 21 years with typical management strategies. Meanwhile, Alzheimer’s disease affords only 12 years.

The findings should change how we think about disease, says senior author Gerard F. Anderson, professor in the Department of Health Policy and Management. "The balancing act needed to care for all of those conditions is complicated, more organ systems become involved as do more physicians prescribing more medications,” he said. In truth, the U.S. health care system isn’t designed to handle co-occurring diseases. Specialized medications have side effects, and those side effects don’t always line up with each disease. “Each one adds up and makes the burden of disease greater than the sum of its parts."

What to do about all this is the larger question. Chronic diseases are in part a personal challenge. Diet-related diseases, such as hypertension and type 2 diabetes, are wholly preventable, barring any genetic predisposition. Neurodegenerative diseases, like Alzheimer’s, which carry no singular root cause, depend more on clinicians to treat. And for those, the researchers suggest funding changes from the top down.

"We already knew that living with multiple chronic conditions affects an individual's quality of life, now we know the impact on quantity of life," DuGoff said. In fact, two-thirds of people older than 67 had three or more conditions. These may be mostly manageable, but what she and her team don’t want to happen is these conditions outpacing the myriad medical advances, and life expectancy to change course.

"The growing burden of chronic disease could erase decades of progress,” she said. “We don't want to turn around and see that life expectancy gains have stopped or reversed."

Source: DuGoff E, Canudas-Romo V, Buttorff C, Leff B, Anderson G. Multiple Chronic Conditions and Life Expectancy: A Life Table Analysis. Medical Care. 2014.