One such inherited factor that could extend the human lifespan by as much as one third in theory has been uncovered, though it may come at the cost of a few inches in height, they added.The research also suggested that use of growth hormone as an anti-ageing medicine might actually be shortening lifespan.The study by Prof Nir Barzilai, Director, Institute for Aging Research, Albert Einstein College of Medicine, New York, revealed that rather than being a passive, haphazard process of wear and tear, some people might be blessed with genes that make them more likely to live to a ripe old age.
Earlier work by a French team showed that mice lacking one copy of the gene IGF-1 lived on average 26 per cent longer than normal, with females enjoying a bigger advantage (33 per cent increase in lifespan) than males (16 per cent increase).
Damping down the same pathway of the metabolism also resulted in extension of lifespan in yeasts, worms, and flies too. And the same pathway was affected by diets low in calories, the only proven way to extend lifespan.
The results, reported in the Proceedings of the National Academy of Sciences, found the same gene was involved in the ''oldest old'' of people, revealing in the long run how to postpone the physiological ageing process.
''Practically, this discovery supports the notion that growth hormone, which is injected as anti-ageing medicine in the US (and other countries) may be dangerous, because it is the people who have low growth hormone levels that are living longer,'' Prof Barzilai told The Daily Telegraph.''So avoiding growth hormone may increase ones longevity,'' he added.
The team has not confirmed yet if longevity could be assured by having low growth hormone action throughout life, or whether it would be enough to have it decreased at a certain age.
''The fact is that growth hormone levels and actions are decreased in old age,'' Prof Barzilai pointed out.