The average length of how long Americans live is declining, according to new research published online by medical journal JAMA.

The report says adults 25 to 54 saw the largest increase in mortality rates, up 6 percent. The report also says the northeast is suffering from the biggest increase in deaths.

Obesity, alcohol-related illnesses and overdoses are mostly to blame.

The U.S. had been making steady progress, as life expectancy increased to 78 years old over the last half century -- but the pace slowed over time.

The average life expectancy is now in the high 70s.

The report says other countries with high income continue to see a steady rise in life expectancy.