“THIS DOESN’T HAPPEN.” That’s how Princeton researcher Anne Case reacted to Post reporter Lenny Bernstein, discussing one of the most concerning pieces of news this year — that U.S. life expectancy declined in 2015, for the first time since 1993. According to the National Center for Health Statistics, Americans died at a younger age, on average, because of increasing mortality from heart disease, strokes, drug overdoses, diabetes, accidents and other causes, pushing the death rate up 1.2 percent.

As the incoming administration prepares to reshape the nation’s health-care system and budget, it should keep in mind the public-health challenges that cannot be solved without government research money, government health campaigns and government support for low-income people. In fact, the challenges may be getting more severe, because baby boomers are aging, requiring more care, and because Americans of many age groups may be living less healthy lives.

One reading of the government’s numbers focuses on “diseases of despair” — suicide, alcoholism and other dangerous drug use — that some research suggests increasingly afflict white Middle America. But it would be too easy to conclude that pressing forward on President-elect Donald Trump’s promises to revitalize white working-class communities would be a magic-bullet response. Too easy, first, because Mr. Trump so far has offered no plan to bring prosperity back to downscale communities and, second, because the government’s numbers suggest a broad problem.

Mortality among African American men rose about as much as it did among white men. Relative to the population as a whole, deaths increased from a wide range of causes. Heart disease was the biggest killer . Some experts suggested that the long-term rise in obesity is taking its toll. Doctors’ prescribing patterns are a major driver of deadly opioid addiction. Other major developed nations are not seeing comparable increases in mortality.

Cancer, though still a major killer, claimed proportionally fewer lives than it did the year before. This could be in part because research is delivering new tools that allow doctors to tailor treatments to specific tumors and encourage people’s immune systems to fight cancerous cells on their own. This is one fruit of federal investment in scientific research. People also are smoking less — a result of government anti-tobacco efforts, one of the most important public-health campaigns ever.

You can’t tell from a single year of data whether we are seeing a trend. Even if not, the public-health challenges are huge: Too many people are dying of preventable causes, and many more are dying of diseases for which research could eventually deliver cures. The next Congress and president appear set on significantly curbing government health programs. They should target real waste, not hobble the government’s ability to improve Americans’ health.