How can it be that Americans are living longer and healthier lives than ever before and yet dying in unprecedented numbers from chronic diseases? Are we confusing risks of proxy conditions for real risks of adverse health events?

Successful people live in the present, but they think seriously about the future. They invest themselves and their resources to make tomorrow better than today and to cushion the inevitable bumps in life's road. Through learned precept or harsh experience, they know that "an ounce of prevention is worth a pound of cure." They've also learned to count their blessings along the way, to temper their worry about the future by appreciating the good fortune they've enjoyed.

We use the same thought process to fashion public health policy. As a society, we have never been healthier nor longer-lived, yet these hard-won achievements are tempered with recognition that many amongst us and elsewhere in the world live Hobbesian lives. We recognize the fragility of our personal health and the imposing shadow of chronic disease in our lives and in our families. We invest ourselves, sometimes wisely, sometimes not, in quests to improve our diet and fitness and otherwise protect our health and that of our loved ones. We crave security in matters inherently uncertain. We sacrifice to prevent potential threats, often accepting taxes and social regimentation, believing that using a seatbelt or getting a flu shot is a reasonable trade-off against injuries in car crashes or a flu pandemic.

Just as we do as individuals, as a society we accept risk trade-offs, but we do it based on our belief that these risks have been fairly described. While each of us has a unique set of risk tolerances, the entire calculus is undermined if the information fed into this vast social "brain" is compromised by poorly-understood data limitations or manipulated by unseen parties with special interest bias.

Not to say that these choices are easy. We are beset, as individuals and citizens, with media coverage of emerging science which often seems conflicting. We hear blaring warnings about health threats and advocates' impassioned appeals for action on divergent strategies based on different diagnoses. It's confusing.

Take, for example, two recent "authoritative" pronouncements. In the new publication from the Department of Health and Human Services (HHS), Health, United States, 2007, a compendium of more than 150 tables reporting data from the Centers for Disease Control and Prevention, as we reported earlier :

Life expectancy is at an all-time high. Females live longer than males, but a baby born in 1900 would live until 1948 (men) or 1951 (women) -- 48 and 51 years, respectively. Boomers born in 1950 will live, on average until 2015 (men) or 2021 (women) -- 65.5 and 71 years, respectively). The new report predicts children born in 2004 will live until 2079 (men) and 2084 (women) -- 75.2 and 80.4 years respectively. We take it for granted, but it's big news. And good news.

Children are healthier. In just the past quarter century, the number of children who died before age 14 has been cut in half -- in half! (since the mid-20th century, the rate has been cut 80%). Youth and teens are 60% less likely to be in "fair" or "poor" health. Almost as good as Ivory Soap, 98.2% of our children are healthy.

Adults are thriving, too. Despite our aging population, the percentage of all people in "fair" or "poor" health has dropped in a decade by more than 10% -- from 10.4% in 1991 to 9.2% in 2005. Physical limitations have also been dropping, from 13.3% to 11.7% over the past eight years while age-adjusted vision- and hearing-impairment, over the same period, have improved a remarkable 65% (dropping from 10% to 3.5%).

Mortality continues to decline. The new figures confirm those we reported earlier this year in comparing the U.S. with Americans' steady salt intakes with mortality figures in Finland which compromised its health improvements as it reduced its population's salt intake. Overall, age-adjusted mortality for all of the leading causes of death are in decline -- cut in half since 1950. In just the past 14 years, deaths from the leading cause, heart disease, have dropped by a third. Deaths from the second-leading cause, cancer, have fallen 14% and the third, stroke, by a whopping 72% (with no reduction in dietary salt). The key is age-adjusting. If we don't die of something in our youth or early adulthood, we reach old age where we (all, eventually) die of "old age" ailments like respiratory infections or Alzheimers's. In fact, the biggest risk of dying is getting old.

But, just as we were feeling that perhaps all the doom and gloom of rising health costs and millions without health insurance, was a manageable challenge, The Partnership to Fight Chronic Disease, a new national coalition of business and labor groups, issued its "Policy Platform" declaring that "rising rates of chronic health problems pose a significant and unsustainable burden on the U.S. health care system" and called for Americans to display "a willingness to enact policies that help Americans better prevent and manage chronic illnesses." The Platform calls on the presidential candidates to "highlight common-sense reforms." Pointing out that 77% of U.S. healthcare costs are due to chronic disease, it cites (other) CDC figures showing two-thirds of American children will develop diabetes leading to "lower life expectancy than their parents." Scary stuff. The Platform throws around a lot of numbers, too, such as alleging that obesity costs society $200 billion a year.

Head-scratching time. What about the other CDC figures that show that overweight Americans are actually healthier than their thinner fellow-citizens ( 1 2 3 4 )? You may remember: the ones CDC issued as revisions to their earlier obesity alert .

Now, let's accept that the people making these analyses are most likely fair-minded advocates for their views. The first thought in sorting this out is the correct one: consult the data; a close reading of the studies may help explain the discrepancies and where the authors of various studies may have claimed more than their data show. There is another possibility, however.

While there is general consensus that preventing cancer or heart disease is better - and likely less expensive - than caring for the victim after a malignant tumor is discovered or a heart attack occurs, the differing statistical worldviews as described in Health, United States, 2007 and the PFCD Platform may come down to how risk is defined.

Take the seat belt example. Unrestrained car drivers and passengers are clearly at greater risk of injury or death than those who "buckle up for safety." We'd never, knowingly, combine the two groups to determine the average risk when the documentation of the very different risk profiles is available.

Transfer that thinking to the question of the risk of high blood pressure. About 20% of Americans have high blood pressure, hypertension. And hypertension is responsible for about 16% of heart disease. The 20% with high blood pressure include, of course, those whose current blood pressure exceeds the defined minimum 140/90 mmHg. But the calculation also includes all those whose blood pressure would have been at the "hypertension" threshold except that they took medications or made lifestyle adjustments to lower their blood pressure. Those who managed their blood pressure (like those with seat belts), surely have a lower risk. Unlike the seat belt example, however, they are all lumped together: "once a hypertensive, always a hypertensive." The group that modified its blood pressure should be considered a separate, lower-risk group. By lumping them together, we inflate the number of people identified at risk and targeted for public health concern.

Better data would, thus, help us understand why we continue to have a large number of people with hypertension while at the same time we have achieved fantastic reductions in the rate of heart disease. Hypertension is often "sold" as a disease when it is, rather, an indicator, a marker, an intermediate variable. We are concerned about heart attacks, strokes and mortality. When it comes to treating this surrogate marker, we must never lose track of the real objective: improving health outcomes, not modifying "risk factors" - especially one that explains only one-sixth of the problem. The body is complex and its systems, redundant and interconnected. Simple solutions may make great headlines, but they don't change the "medical facts of life."

So, as we marshal our resources and prioritize our public health targets, let's keep in mind that efforts to prevent chronic disease must be assigned using real-world data. We can prevent high blood pressure, but if the side-effects (e.g. increased insulin resistance, elevated plasma renin activity, etc.) impose unanticipated costs, we need to prevent heart attacks using the best weapons we have. And those weapons are proven. They include medications. They may include lifestyle interventions like weight control and fitness. They don't include salt reduction for the general population.