The rise in drug-related deaths in America -- particularly from opioids like painkillers and heroin -- has taken close to three months off US life expectancy, researchers said Tuesday.

Opioids alone contributed to a loss of 2.5 months -- or 0.21 years -- in life expectancy, said the research letter published in the Journal of the American Medical Association.

The study, led by researchers at the US Centers for Disease Control and Prevention, aimed to narrow down the effect of drug use on US life expectancy, which began to tick downward in 2015 for the first time since the AIDS crisis of the 1980s.

Deaths from drug poisoning have more than tripled in the United States since the year 2000.

Overall, this surge in drug-related deaths has taken 3.36 months off average US life expectancy.

"Between 2000 and 2015, life expectancy increased overall but drug-poisoning deaths contributed a loss of 0.28 years," said the letter in JAMA.

"This loss, mostly related to opioids, was similar in magnitude to losses from all the leading causes of death with increasing death rates during this period combined."

Increases in deaths from unintentional injuries, Alzheimer disease, suicide, chronic liver disease and septicemia all together contributed to a loss of 0.33 years in life expectancy.

Overall, life expectancy at birth in the United States has increased by two years since 2000, when it was 76.8 years -- to 2015 when it rose to 78.8 years.

These gains have been driven by dropping rates of death from top killers like heart disease, cancer, diabetes, influenza and pneumonia, and kidney disease.

But the effect of opioid deaths was noticeable.

More than 17,000 deaths in 2000 were attributed to drug overdoses compared to more than 52,000 in 2015.

Previous research has shown that after years of increasing life expectancy, the trend began to reverse in recent years, particularly among whites.

"US life expectancy decreased from 2014 to 2015 and is now lower than in most high-income countries, with this gap projected to increase," said the letter.

Drug-related deaths are likely an underestimate due to limits on the accuracy and completeness of information recorded on death certificates, researchers added.

A specific drug is not recorded in as many as 25 percent of drug-poisoning deaths.

Source: AFP