Motor vehicles and firearms kill young Americans more than any other cause, like disease, which has significantly declined, according to a new study.

The New England Journal of Medicine reports that less than 2 percent (or 20,360) of all U.S. deaths — including adults — occur among children and adolescents 1 to 19 years old.

"By 2016," the year for which the most recent data are available, "death among children and adolescents had become a rare event," study authors Dr. Rebecca M. Cunningham, Maureen A. Walton and Dr. Patrick M. Carter of the University of Michigan in Ann Arbor wrote in the Dec. 20 edition.

But in the second largest cause of death among young people — death by firearms — the U.S. leads the world.

"The rate of firearm deaths among children and adolescents was higher in the United States than in all other high-income countries and low-to-middle-income countries with available 2016 data," the authors wrote, or 36.5 times as high as 12 other "high-income" countries.

Data for 2017, which are not included in the NEJM article, show a continued increase in firearm deaths for children and adolescents, Cunningham said.

"One in three U.S. homes with youth under 18 years of age has a firearm, with 43 percent of homes reporting that the firearm is kept unlocked and loaded, which increases the risk of firearm injuries," the authors reported. "In addition to differences in availability between the United States and other countries, there is wide variability across countries in laws relating to the purchase of firearms, access to them and safe storage."

At the same time, "early diagnosis, vaccinations, antibiotics, and medical and surgical treatment" resulted in "declines in deaths from infectious disease or cancer," the report said.

And while motor vehicle events were the leading cause of death for young people, that cause has declined 38 percent over the past decade, the authors wrote.

What caused the declines?

"Seat belts and appropriate child safety seats, the production of cars with improved safety standards, better constructed roads, graduated driver licensing programs, and a focus on reducing teen drinking and driving," the authors wrote, noting that the decline occurred at the same time as increases in the number of U.S. vehicles and annual vehicle-miles traveled.

But there's a hitch: Between 2013 and 2016, research showed the decline leveling. And while researchers said they didn't know for certain, they suspected that distracted driving by teenagers, by other teens in a car or by cellphone use, explained the leveling. The report also wondered about marijuana use and drugged driving leading to "decreased risk perceptions among adolescents."

Among firearm deaths, 59 percent were homicides, 35 percent were suicides, and 4 percent were unintentional injuries such as accidental discharges of firearms, which aligns with incidents among Americans older than 20.

Death by firearms

Among the unintentional firearm deaths — less than 2 percent of all U.S. firearm deaths — 26 percent occurred among children and adolescents, the report said.

"Malignant neoplasms," like cancer, were the third-leading cause of death, representing 9 percent of deaths among children and adolescents. That was followed by suffocation (7 percent) because of "bed linens, plastic bags, obstruction of the airway, hanging or strangulation."

Among the youngest children, 1 to 4 years-old, drowning in swimming pools, rivers and lakes was the most common cause of death, the report said. Death by drowning was more rare in older children, "which potentially reflects widespread swim training among school-aged children."

Among youth 10 to 19 years of age, injury deaths from motor vehicle crashes, firearms and suffocation were the three leading causes. Researchers said these causes reflected "increased risk-taking behavior, differential peer and parental influence, and initiation of substance use."

Drug overdoses or poisonings rose to the sixth-leading cause of death among children and adolescents in 2016, the report said, attributed to an increase in "opioid overdoses, which account for well over half of all drug overdoses among adolescents."

Mortality was higher among blacks (38.2 per 100,000) and American Indians or Alaska Natives (28.0 per 100,000) than among whites (24.2 per 100,000) and Asians or Pacific Islanders (15.9 per 100,000), the authors wrote. Deaths related to firearms were the leading cause of death among black youth and occurred 3.7 times the rate of such deaths among white youth.

Drowning deaths

Black youth also had higher rates of drowning deaths (1.6 times as high) and fire-related deaths (2.3 times as high) than white youth. Blacks had death rates from heart disease and chronic lower respiratory diseases such as asthma that were 2.1 and 6.3 times as high, respectively, as the rates among white youth.

"Such disparities probably reflect underlying socioeconomic issues, including poverty, environmental exposures and differential access to health care services," the researchers wrote.

"Progress toward further reducing deaths among children and adolescents will require a shift in public perceptions so that injury deaths are viewed not as 'accidents,' but rather as social ecologic phenomena that are amenable to prevention." the authors concluded.

Researchers compiled their report on data from the Wide-ranging Online Data for Epidemiologic Research (WONDER) system of the Centers for Disease Control and Prevention (CDC) from 57 vital-statistics jurisdictions.