NEW YORK (MarketWatch) -- How long can you expect to live? The answer to that tantalizing question tells a lot about the success of a nation -- or the lack of it.

If the people in some countries tend to live several years longer than the global average (as they do in, say, Japan or Singapore or most European nations) that suggests that their populations are generally healthy. But if they are below the global average, that suggests they drink too much alcohol or have other unhealthy habits (as is the case in, say, Russia).

The U.S. performed spectacularly well in the longevity competition during the 20th Century. Longevity in America famously surged from an average 47 years in 1900 to 77 years in 2000. We can credit many factors, including the virtual elimination of malaria, small pox and many childhood diseases.

Not only are Americans living longer, they are also working for more years than their forebears and they are retiring later. This is partly because they have to continue working in order to support themselves in a slower economy and also, in many cases, because they wish to stay active and alert.

The problem with this triumphant prolongation of life is that the gains in U.S. longevity have slowed in the last five years or so and this has alarmed scientists and policy makers who study it.

Dr. Robert Butler, 81, the influential and prescient physician who is CEO of the International Longevity Center in New York, believes that at least four forces are at work here:

The shockingly high infant mortality rate in the U.S. Mostly because so many babies are born in urban slums and country hollows, where prenatal and infant care is often primitive, America has the second steepest newborn mortality rate among developed nations. In 2005, the latest year for which statistics are available, about seven out of every 1,000 babies in the U.S. died before their first birthdays. Though there has been steady improvement for many years, the U.S. is 29th in the world, behind even Cuba. The multibillion dollar political power of the industries that contribute to the steep rate of obesity among U.S. children and adults, such as fast foods and sugared drinks. Butler urges that the U.S. government create public-private initiatives to promote healthier diets and physical fitness programs among the public at large. The estimated 46 million Americans (15.8 percent of the population) who do not have health insurance and thus lack the kind of medical care that would expand and enhance longevity. The slowdown in medical research in the U.S. Especially absent is the kind of what-makes-the-sky-blue basic research usually conducted by younger scientists and technicians, who tend to be the most innovative, daring, productive -- and successful when it comes to life-expanding discoveries.

The main support for basic medical research in the U.S. is not universities or drug manufacturers but the government, notably the National Institutes of Health. The NIH's budget has been flattened since 2003 -- hovering around $29 billion -- with the result that the rate of discoveries has slowed. Among them, presumably, are the kinds of discoveries that would add to longevity.

Another factor, says Butler, is the researchers who receive NIH grants are getting older. Butler reckons that the average age of researchers receiving their first NIH grant is about 42, whereas he believes it should be 28 or 30.

The encouraging news is that all these challenges can be addressed -- provided the nation has the will to do so. Indeed, the new administration of President-elect Barack Obama and Congress in Washington are already committed to make health-care reform one of their immediate and massive issues.

If they add to that the commitment to battle infant mortality, obesity and the flattening of medical research, they will create a new and needed strategy for making American longevity even more vital.