The Challenges of Longevity; The Science of Staying Young; Special Editions; by John Rennie; 1 Page(s)

It started about a hundred years ago. As improved health care, sanitation and nutrition became more available, we began to make dramatic strides in thwarting the forces that had traditionally shortened human existence. In 1900 some 10 million to 17 million people were aged 65 or older, and they made up less than 1 percent of the world's population. Survival rates began to climb for infants, children and women of childbearing age, gradually lifting humanity's average life span. By 2000, 606 million were aged 60 or older, and they made up almost 10 percent of the world's population. According to the United Nations report World Population Prospects, by 2050 that group could swell to 1.9 billion and constitute one fifth of the world's projected population. The fastest-growing segment is the so-called oldest old, those aged 80 and above. In 2000, 69 million people were in that category, and in 2050 their number could reach 377 million.

But it is not enough simply to live longer. Merely accruing additional years beyond the biblical span of three score and 10 would be unwelcome if they just prolonged suffering from illness and infirmity. No, we want to live better, more youthful days while we're living longer. Diet, exercise and a lucky draw from the gene pool can take us only so far, however. That's where science comes in. In this special edition from Scientific American, you'll find firsthand reports from the researchers leading the efforts to understand the mechanisms of aging. They are teasing out ways to slow the biological clock as well as the degradation that time imposes on our bodies and minds. They are battling the diseases of age, including cancer and heart disease.