Something astounding is happening. For most of human history, life expectancy was barely long enough to ensure survival of the species. During the 20th century, a blink of an eye in evolutionary terms, Americans began flourishing into their 80s, 90s and beyond. Asked in a recent survey about the prospect of century-long lives, the majority of Americans said they would like to live 100 years if they could do so in good health. Of course, in the same survey, nearly as many Americans said they want to retire at 65, and most of them said they eat too much and tend not to exercise. Hope is wonderful, but hope alone will not get us to 100 in good shape.
An important first step in creating a culture that supports long life is recognizing that long-term planning doesn't come naturally to humans. Nothing in our evolutionary heritage prepared our brains to think clearly about the distant future or, for that matter, to take much notice as the effects of our daily habits--which accumulate over the course of many years--begin to present themselves. Research also makes plain the fact that humans have a hard time imagining the potential negative consequences of their actions. Yet the quality and of course the length of life rest squarely on the cumulative effects of those habits over decades. (For more on the latest findings about lifestyle changes that give humans an edge, see page 80.)
It is clear that people can thrive at advanced ages; indeed, many already do. But if we are to realize the vast opportunities that a record number of longer lives presents for the nation, we need to engage in an unprecedented level of planning and foresight. We also need to take stock of where we stand today, so we can have a better sense of what we need to work on for a healthier--and more financially secure--tomorrow.
To help address these problems, the Stanford Center on Longevity, which I founded in 2007, embarked on a continuing effort we call the Sightlines Project. Its premise is that in order for the U.S. population to age well in the 21st century, we need a clear vision of the ways in which its strengths and vulnerabilities are likely to play out. In early 2014, we gathered a diverse set of scientists from medicine, economics, social epidemiology and psychology, as well as experts from industry and policy, and asked them to identify known practices or behaviors that are associated with long and healthy lives.
We focused our attention on three key modifiable practices: healthful living, financial security and social engagement. Some factors, like the need for exercise, are already appreciated by most Americans. Others are less obvious. Failing to invest in your financial future or your close social relationships threatens long-term health too. Research has made clear that strong social ties are linked to better health--and not just because they mean someone will be around to help you if you need it. Strong relationships are also linked to a better outlook and reduced stress--two things that have been shown in studies to have a biological impact on how someone ages.
The next step was to search for good metrics in large-scale studies that could alert us to recent trends. That digging delivered good news and bad news. For instance, smoking rates continue to decline, and more Americans are exercising. But most still need more exercise--and unfortunately, we are also sitting more.
We are hurting financially in ways that have long-term consequences; no age group is doing better financially than it was a little over a decade ago, and millennials are being hit hardest. It is painful to note that young people who managed to get to college are now saddled with increasing debt, a situation that has worsened in recent years and that is associated with lower rates of homeownership and investing.
And though the majority of Americans report having strong social ties, there are disturbing patterns being seen in people in their 50s and 60s. Baby boomers interact less with their neighbors as well as their families than did people their age 20 years ago.
It should come as no surprise that a culture that evolved over the millennia to support short lives has so far failed to optimize long ones in these three key ways. And though progress is being made, things have changed so rapidly. For instance, dementia was hardly a threat to public health 50 years ago; rather, it was a problem for a handful of unfortunate individuals and their families. Today Alzheimer's is on track to become an epidemic, with nearly 14 million Americans expected to live with the disease by 2050 unless promising drugs and other interventions can stop it. (To learn more about work to develop a new Alzheimer's drug, see page 64.) Similarly, neither sitting nor obesity was a problem when most Americans worked on family farms. Now, sitting is a risk factor for obesity, which in turn is a risk factor for diabetes, which is strongly associated with dementia. Clearly, optimizing longevity--and the quality of that longer life--demands a clear line of sight that spans decades.
The social world is changing just as profoundly. Because families have fewer children, there are fewer siblings and cousins. Yet families now include more generations than ever before. Globalization is not simply an economic phenomenon, it's also a social one. Because people don't grow up and grow old in the same place with the same people, communities have changed. More and more young people don't look to neighbors and family friends for mates; instead they contemplate mates who span continents and cultures. Friendships, collaborators and romantic partnerships depend less on physical proximity and more on common interests and concerns. Similarly, contact with local communities--especially religious organizations--is waning.
Because social media is still so new, we know little about its role in the formation and strength of social bonds. We do not know how such exchanges across geographical distances strengthen or weaken emotional engagement over time.
Finally, the nation is failing when it comes to financing long lives. Our problems today stem in part from human foibles, like the failure to delay gratification, and in part from uphill struggles to secure education and sufficient income. Taking the long view, it is clear that we must save more and work longer. Ensuring that all Americans can do so is essential in order for the nation to thrive. Paraphrasing my Stanford colleague John Shoven, the vast majority of Americans cannot finance 30-year retirements with just 40 years of work.
It will be difficult for the U.S. to change its ways to support long and satisfying lives, but we've risen to even bigger challenges in the past. A short century ago, as many as 30% of babies born in some U.S. cities died before the age of 5, malnourishment was rampant, and infectious diseases left hundreds of thousands of people disabled. Our ancestors made reasoned decisions to invest in science and technology and education. They established public-school systems in every state in the nation, and the government funded the research necessary to make key advances in medicine.
Their efforts were so effective that diseases like polio and smallpox were essentially eradicated. Infant mortality declined dramatically. Health greatly improved. Teaching all children how to read and write improved the productivity of the country. Today educational attainment early in life predicts not only quality but ultimately length of life. The fact that gains in life expectancy are now leveling off and, according to recent reports, declining among subgroups of Americans who have relatively little education is a testament to the powerful role that education continues to play.
American optimism, often disparaged and seen as naive, will go a long way in addressing challenges related to longevity. Optimism can encourage bold investments in science and technology that can solve scores of problems associated with long life. Given the breathtaking capacity of modern science, armed with spectacular new tools represented in Big Data, computational genomics and flexible electronics, the greatest threat of failure will be setting the bar too low.
To fully use our added years--and to improve their quality--we will need to change the way we live. Although change will be hard, redesigning our world to accommodate long life may represent the greatest opportunity of our time.
Carstensen is the founding director of the Stanford Center on Longevity