Life expectancy at birth in the U.S. fell slightly in 2016 -- to 78.6 years from 78.7 years in 2015, according to the CDC's National Center for Health Statistics (NCHS).

The changes are the first consecutive declines in life expectancy at birth since the early 1960s, the CDC said, and they come 3 years after the record high of 78.8 years.

They also come after a statistical analysis earlier this year suggested gains in life expectancy over the next few decades will be the rule in most industrialized countries, but the U.S. will be among the poorest performers.

Life expectancy at birth is a statistical construct that assumes current mortality rates for various age groups will apply throughout the lives of babies born in a given year. It is heavily influenced by death rates at younger ages, including infant mortality.

In 2016, the decline in life expectancy was entirely for males -- to 76.1 years in 2016 from 76.3 in 2015 -- but for females, life expectancy remained the same at 81.1 years.

NCHS estimated life expectancy for people reaching age 65 at another 19.4 years in 2016 compared with 19.3 in 2015. Life expectancy for men age 65 was unchanged at 18 more years, but the odds for women improved slightly, to 20.6 years from 20.5.

Age-adjusted death rates for the total population fell significantly, from 733.1 per 100,000 standard population in 2015 to 728.8 in 2016, or 0.6%. But death rates for specific ages varied, with significant increases among younger age groups and decreases among their elders. Specifically, death rates rose 7.8% among those ages 15-24 years, 10.5% among those ages 25-34, 6.7% among those ages 35-44, and 1% among those ages 55-64.

Death rates decreased 0.5% for those ages 65-74, 2.3% for those ages 75-84, and 2.1% for people ages ≥85.

The 2016 infant mortality rate -- 587 infant deaths per 100,000 live births -- was not significantly different from the 2015 rate of 589.5 per 100,000 live births.

There were also variations in the age-adjusted death rate by race and ethnicity, according to the report. Specifically, death rates increased 1% for non-Hispanic black males and fell 1.1% for non-Hispanic white females; there were no significant differences for other racial or ethnic subgroups.

The 10 leading causes of death remained the same in 2016 as in 2015:

Heart disease

Cancer

Unintentional injuries

Chronic lower respiratory diseases

Stroke

Alzheimer's disease

Diabetes

Influenza and pneumonia

Kidney disease

Suicide

But unintentional injuries, which had been the fourth leading cause of death in 2015, rose to third, while chronic lower respiratory diseases fell to fourth.

For most of those causes, which account for some 74.1% of all deaths in the U.S., the age-adjusted death rates decreased. Specifically, death rates fell for heart disease, chronic lower respiratory diseases, stroke, diabetes, influenza and pneumonia, and kidney disease. Rates rose for unintentional injuries, Alzheimer's disease, and suicide.

Life expectancy has been rising world wide, although the U.S. usually lags behind other industrialized countries. An earlier analysis in the The Lancet argued that the lag is likely to worsen. Majid Ezzati, FMedSci, of Imperial College London, and colleagues projected that by 2030 U.S., life expectancy at birth might be "similar to the Czech Republic for men, and Croatia and Mexico for women."

They noted that the U.S. has the "highest child and maternal mortality, homicide rate, and body-mass index of any high-income country" -- all factors that can influence life expectancy. They also cited "high and rising health inequalities" as a factor in their analysis.