US life expectancy is up for the first time in four years, driven by factors including a fall in the rate of fatal drug overdoses and cancer deaths, official statistics showed Thursday.

The increase in 2018, the latest year for which data is ready, was marginal: 78.7 years compared to 78.6 years for the year before, but it was enough to arrest a slide that began in 2014.

The figure was 76.1 for men and 81.2 for women.

"This has not happened through coincidence, it's happened through causation," said White House advisor Kellyanne Conway, announcing the figures. "It's owed in large part to a whole of government approach to treat the whole person, led by President Trump."

The government also said that 2018 saw the first decline in drug overdose deaths in almost three decades, confirming preliminary data that was announced last year.

There were more than 67,000 drug overdose deaths in the United States in 2018, a four percent decline from 2017 when there were just over 70,000 deaths.

But that still leaves 2018 as the second-worst year on record, with the rate of overdose deaths around triple what it was in 1999.

And the rate of drug overdose deaths involving synthetic opioids such as fentanyl, its analogs, and tramadol increased by 10 percent compared to the previous year.

Fentanyl, used medically as an intravenous anesthetic, can be lethal in a dose of as little as two milligrams, equivalent to a few grains of sand.

Despite overall good news on the life expectancy front, with death rates also down for heart disease, stroke and Alzheimer's, there were some negative factors too. The suicide rate ticked up 1.4 percent while the influenza and pneumonia death rate rose 4.2 percent.