Here's Why

How long is the Hayflick Limit? Try 300 years.

I found my first reference today that lets me translate the Hayflick Limit on human cells into years of life. New Scientist talks about obesity and cigarettes and ageing from a paper published in The Lancet. A new study from St Thomas Hospital in London focussing on the effects of obesity and smoking on aging, has also shed light on what has often been touted on the upper limit of how long people can live: The Hayflick Limit. The Hayflick Limit was discovered by Leonard Hayflick in 1961, and it refers to the fact that normal human body cells are mortal. Telomeres are the fuse that burns down every time a cell replicates, so that when its “boom” time, the cell stops replicating and starts to clog up with waste and eventually dies. In bottles, they reproduce fifty times, before they stop replicating. This has been compared to aging of the human body, and suggested as part of the aging mechanism - although nobody has any proof, yet. However until now, nobody has published the figures to translate from fifty cell replications in the lab, into how many years of life you could reach if all diseases and injuries were healed, before your cells stopped replicating and just died. Tim Spector measured the length of the telomere fuse as it burned down in a study of 1122 women, and importantly, the rate at which it burned down. He also looked at the effects of obesity and smoking, and its no surprize that they make you age much faster. Even if we cure all diseases and heal all injury, as long as we're flesh, the Hayflick Limit would kill us in the end. So how long would that give us? In his study at St Thomas’ Hospital in London, Tim Spector measured the length of the telomeres of 1122 women, and found that in 18 year olds, the telomeres were 7500 base pairs of chromosomes long. Now the telomeres shortened at an average rate of 27 base pairs per year. By simple back of the envelope calculations, that gives them 277 years of life before their cells stop replicating. Since they started at 18 years of age, that means they get on average, 295 years of life! I feel confident in saying that nobody on record has lived long enough to be killed by the Hayflick Limit. I’ll worry about it getting my telomeres lengthened when I'm halfway there at a young 142.

About the author: Ian Woolf lives in Sydney, has a degree in Applied Science, worked as a solar astronomer, software engineer, systems programmer, webmaster, research assistant, Cisco CCNA tutor, Physics laboratory demonstrator, Computational Theory lecturer, and subject coordinator; while changing his career to freelance writing and broadcasting. Listen to Ian on the Diffusion radio science show on radio 2SER 107.3FM Monday at 6:30pm in Sydney or streaming audio on www.2ser.com, or listen to the Diffusion podcasts. You should follow me on twitter, here

Posted by iwoolf at June 23, 2005 5:09 PM