Nearly 80% of older Americans are now living with multiple chronic medical conditions, and the more ailments people have after retirement age, the shorter their life expectancy, a new US study shows.

Life expectancy in the US is rising more slowly than in other parts of the developed world, and this is widely blamed on the obesity epidemic and its related health conditions. However, 60% of people aged 67 and older in the US are now living with three or more chronic conditions, and the medical advances that have allowed sick people to live longer may not be able to keep up with this growing burden, say the researchers, from the Johns Hopkins Bloomberg School of Public Health.

Eventually, there may be a tipping point, when the medical advances that have boosted life expectancy for so long can no longer keep pace with the many illnesses that people are collecting as they age, they warn, reporting their findings in the August issue of the journal Medical Care.

On average, a 75-year-old American woman with no chronic conditions will live to just over age 92, but with five chronic conditions she will live on average to 87, and with 10 or more chronic conditions she will survive only to 80, they find.

Which diseases people have also matters. At age 67, an individual with heart disease will live an additional 21.2 years on average, while someone diagnosed with Alzheimer’s disease is only expected to live 12 additional years. And while life expectancy is reduced by 1.8 years on average with each additional chronic condition, the impact grows as the diseases add up.

Lead author Eva Du Goff points out that living with multiple chronic conditions such as diabetes, kidney disease and heart failure is now the norm, not the exception, in the US.

“It is becoming very clear that preventing the development of additional chronic conditions in the elderly could be only way to continue to improve life expectancy,” she says.

“We tend to think about diseases in isolation. You have diabetes or you have heart failure. But many people have both, and then some,” adds senior author Gerard Anderson.

“The balancing act needed to care for all of these conditions is complicated - more organ systems become involved as do more physicians prescribing more medications. Our system is not set up to care for people with so many different illnesses. Each one adds up and makes the burden of disease greater than the sum of its parts,” he says.