Prolonging life

It was reported in 1999 that the life of a species of roundworm had been extended by a genetic alteration. Mutations in a single gene allowed the worms to live for a month instead of two weeks and to maintain good health into old age. It was also found that the mutated gene was closely related to genes that cells used to respond to several hormones, including insulin, raising questions of whether there might be a simple hormonal treatment to retard aging substantially.

According to a 1999 report, two mouse strains which are small in size live 50 percent to 75 percent longer than normal. Gene mutations affect cells of the pituitary glands preventing the animals from making hormones such as growth hormone, thyroid hormone and prolactin. These dwarf mice grow to one-third the normal size and are not fertile. Some have suggested that this is similar to other animals: that small dogs live much longer than large ones and even small grasshoppers live longer than bigger ones. No properly controlled studies have been done to say whether the same is true for people.

For the past 160 years the top life expectancy has increased by a quarter of a year every year and the rate is not slowing. it is predicted that the top life expectancy will continue to increase by 2.5 years each decade, meaning that the world's top average life expectancy should reach 100 within the next 50 years.

According to the annual mortality report published by the Centers for Disease Control and Prevention, an American male born in 2000 has a life expectancy of 74.1 years, which is 0.2 years greater than in 1999. An American female born in 2000 has a life expectancy of 79.5 years, which is 0.1 years greater than in 1999. In addition, the gap in life expectancy between the sexes is narrowing. In 1990 there was a 7-year difference between the sexes, compared to 5.4 years in 2000.

A study of 17,000 Harvard alumni found that men who burned 500 to 1,000 calories a week on physical activity (the equivalent of walking 5 to 10 miles) had a 22% lower risk of death for all causes, while those who expended 2,500 calories a week also added 1 to 2 years to their extended life span. Another showed that each additional decade that parents lived, their offspring scored higher on tests of mental performance, and were increasingly less likely to have diabetes, high blood pressure, heart disease, heart failure, stroke or general poor health.

A team of Icelandic researchers say that they have identified the so-called Methuselah gene - the gene responsible for a long and healthy life. The researchers located the gene after comparing the records of 1,200 people who lived for 90 years or longer with that of a similar number of people with average lifespans. The discovery follows that of a group of Harvard researchers who found that 100% of the centenarians they studied had Methuselah-type genes, which appeared to protect them from age-related conditions such as cancer, dementia and heart disease. Many had also inherited a gene dubbed the longevity gene. The researchers also found that the children of centenarians were likely to live 10-15 years longer than the norm, and their siblings were four times more likely than average to live to see their 90th birthday.