After decades of improvement, life expectancy in America is no longer on the rise.

Over the past few years, the increasing longevity that was once the norm has stalled out. In 2015 American life expectancy actually declined, year-on-year, by about a month, shrinking to 78.8 years. So we read this week in the Wall Street Journal, under the headline "Nation's Death Rate Rises as Progress Against Heart Disease Stalls," and in USA Today's dispatch, "Has U.S. life expectancy maxed out? First decline since 1993."

Similar alarms have been clanging for some time now, including three stories in the New York Times last year: "Death Rates Rising for Middle-Aged White Americans, Study Finds"; a report this June on the broader trend, "First Rise in U.S. Death Rate in Years Surprises Experts"; and a story this September titled "Maternal Mortality Rate in U.S. Rises, Defying Global Trend, Study Finds."

In story after story, we read about demographers and medical experts puzzling over what's gone wrong. They point to heart disease, obesity, drug use, stroke, Alzheimer's, suicide. The USA Today article notes that since World War II, it's been rare to see a rise in U.S. mortality rates, and such spikes have usually been linked to highly specific events such as the spread of AIDS in the early 1990s, or a "nasty flu season" in 1980. By contrast, what we're seeing now are rising mortality rates involving a broad range of causes, especially among middle-aged Americans.

Missing from all these accounts is a single word that ought to command unblinking attention: Obamacare.

Or, if you prefer the full title: The Patient Protection and Affordable Care Act of 2010, also known as the signature achievement of Obama's first-term. It is a big part of his legacy, a cornerstone of his 2008 campaign promise of "fundamentally transforming the United States of America." It is a big part of the legacy Obama is now urging President-elect Donald Trump to preserve.

Is it sheer coincidence that the timeline of the flat-lining and decline of American life expectancy overlaps neatly with the enactment, rollout, and implementation of Obamacare?

Demography is a complex field, and mortality statistics may reflect many factors. But behind the roster of proximate health reasons blamed for the decline in American longevity and the rise in maternal mortality rates, surely it makes sense to ask whether broad government policy could be a factor. Especially when that policy has been designed quite deliberately to reshape the roughly 16% of the American economy devoted to healthcare, with knock-on costs and constraints across a multitude of other sectors.

In the case of Obamacare, as we all know, Obama promised that costs would go down, care would improve, "if you like your healthcare plan, you keep your healthcare plan," and "if you like your doctor, you can keep your doctor."

As huge numbers of Americans have learned firsthand, these were lies.

Since Obama signed the Affordable Care Act into law in 2010, without a single vote of support from the Republican Party, what has transpired for many Americans has been the ruinous equivalent of a tsunami hitting the country's medical system — leaving many Americans trying to cling to the sinking flotsam.

First came the mad scramble to find out what was in the indecipherable tome of the Affordable Care Act — of which Rep. Nancy Pelosi famously said, "We have to pass the bill so that you can find out what is in it." Then, while Americans were still trying to navigate the thousands of pages of related regulatory kudzu, along came the hideously botched rollout in 2013 of the enrollment site — fixable in its more technical aspects, but also a flashing red warning of what tends to happen when government tries to micro-manage an industry.

Doctors and patients alike have been swamped with paperwork. An entire industry has sprung up, battened onto the actual practice of medicine, in which Americans are effectively forced to pay — whether directly or via complex cross-subsidies — for legions of bureaucrats, consultants and "navigators." They either dictate terms, or at least in theory know how to read the roadmaps that might get you, at least for a while, to a health care plan, or doctor.

Networks have narrowed, costs have soared, premiums have skyrocketed, and the promised choices to be offered in the fake "marketplace" of the state-subsidized exchanges have been vanishing, as insurers have left.

Middle-aged Americans have been told to comfort themselves that they are perforce contributing to the contraceptive needs of Georgetown Law School students.

Obama, apparently indifferent to the quality or actual delivery of medical care, brags that millions more Americans are now covered. Never mind the shrinking choices, rising deductibles, and disappearing access to doctors.

Could all this, just perhaps, have something to do with the rising mortality rates that are now, reportedly, baffling so many experts?

It's a question that needs asking, big time, especially with some of these experts recommending yet more state intervention as a cure.

The Wall Street Journal article on America's rising death rate quotes one such expert saying that "More public health measures — such as policies to reduce smoking and help people lose weight — will be needed to make inroads." No doubt it would help to have fewer smokers and less obesity, but there's hardly been a dearth of public programs on such fronts. If obesity is a rising problem, after years of Michelle Obama's campaign to strong-arm public schools into serving inedible low-salt, whole-grain, low-calorie lunches (to which her own daughters have not been subjected), surely it's time to ask whether "public health measures" are more cause than cure.

There's been a lot of speculation that the real aim of Obamacare, with its actuarial "death spiral," was always to drive private medicine and private health insurance out of business, and ultimately replace it across the board with a so-called "single-payer" system. In plain English that means socialist medicine, an entirely nationalized, government-monopolized health care industry. That's the kind of system which in years past, in other countries where it has been imposed, has sent patients (at least those who can afford it) fleeing to the U.S. for better care.

Trump has promised to rid America of this unaffordable "Affordable Care Act" — a legacy of miseries to which Obama himself has never personally been subjected, nor have the members of the 2010 Democratic majority congress who passed it. They exempted themselves.

Let's hope Trump sticks to his word. That would be a legacy worth honoring, not least because it's a good bet that a lot of Americans would enjoy longer lives in which to honor it.

Ms. Rosett is Foreign Policy Fellow with the Independent Women’s Forum, and a foreign affairs columnist for