According to the World Health Organization, there were 600 million people aged 60 and over in the year 2000.
This number will increase to 1.
2 billion by 2025 and 2 billion by 2050.
Today, about two thirds of all older people are living in the developing world and by 2025, it will be 75%.
The United States is on the brink of a longevity revolution.
By 2030, the number of older Americans will have more than doubled to 70 million, or one in every five Americans.
The growing number and proportion of older adults, places increasing demands on the public health system and on medical and social services.
In just 10 years, spending on the elderly will total nearly $1.
8 trillion, almost half the federal budget, according to new Brookings Institution and Congressional Budget Office projections.
That is up from 29 percent in 1990 and 35 percent in 2000.
The bulk of that growth is spending on the federal government's two largest health care programs, Medicare and Medicaid.
Their combined costs are projected to more than double, to a combined total of $1.
2 trillion in 2015 from $473 billion last year.
Social Security spending is expected to rise to $888 billion from $492 billion in that span.
Chronic diseases exact a particularly heavy health and economic burden on older adults due to associated long-term illness, diminished quality of life, and greatly increased health care costs.
Although the risk of disease and disability clearly increases with advancing age, poor health is not an inevitable consequence of aging.
Aging is an accumulation of lifelong damage to macromolecules, cells, tissues and organs.
The maximum life span known for humans is 122.
5 years.
Genetic differences between humans account for different aging rates, including efficiency of DNA repair, types and quantities of antioxidant enzymes, and different rates of free radical production.