With his beard and robust opinions, there's something of the Old Testament prophet about Aubrey de Grey. But the 47-year-old gerontologist (who studies the process of ageing) says his belief that he might live to the very ripe old age of 1,000 is founded not on faith but science. De Grey studied computer science at Cambridge University, but became interested in the problem of ageing more than a decade ago and is the co-founder of the Sens (Strategies for Engineered Negligible Senescence) Foundation, a non-profit organisation based in the US.

What's so wrong with getting old?

It is simply that people get sick when they get older. I don't often meet people who want to suffer cardiovascular disease or whatever, and we get those things as a result of the lifelong accumulation of various types of molecular and cellular damage. This is harmless at low levels but eventually it causes the diseases and disabilities of old age – which most people don't think are any fun.

Is this the biggest health crisis facing the world?

Absolutely. If we look at the industrialised world, basically 90% of all deaths are caused by ageing. They are deaths from causes that affect older people and don't affect young adults. And if we look at the whole world, then the number of deaths that occur each day is roughly 150,000 and about two-thirds of them are because of ageing.

Why does the world not recognise this?

People have been trying to claim that we can defeat ageing since the dawn of time, and they haven't been terribly successful; there is a tendency to think there is some sort of inevitability about ageing – it somehow transcends our technological abilities in principle, which is complete nonsense.

And when people have made their peace with this ghastly thing that is going to happen to them at some time in the distant future, they tend to be rather reluctant to re-engage the question when someone comes along with a new idea.

Is it that our bodies just stop being so proactive about living?

Basically, the body does have a vast amount of inbuilt anti-ageing machinery; it's just not 100% comprehensive, so it allows a small number of different types of molecular and cellular damage to happen and accumulate. The body does try as hard as it can to fight these things but it is a losing battle. So we are not going to be able to do anything significant about ageing without hi-tech intervention – which is what I'm working on.

Ageing involves the process of metabolism, and then deterioration, and then pathology – is that right?

Basically, that's right. Metabolism involves a vastly complicated network of biochemical and cellular processes that are linked and that succeed in keeping us alive for as long as they do, but they have these side effects.

The side-effects start even before we are born, they go on throughout life and they are manifested as, for example, the accumulation of various types of molecular garbage inside cells and outside cells, or simply as cells dying and not being automatically replaced by the division of other cells. Gradually those changes at the molecular and cellular level accumulate and accumulate and eventually they start to get in the way of metabolism, and that's where pathology comes.

You've identified seven particular areas of cellular decay that might be combated. Can you give examples?

I just mentioned cells dying and not being automatically replaced, that's one. Another is cells not dying when they ought to – certain types of cells are supposed to turn over and sometimes they lose the ability to respond to signals that tell them to die.

A third is cells dividing too much – they may be dying when they are supposed to but dividing too much, and that is what cancer is.

We've known what causes cancer for some time but we are a long way from being able to cure it, aren't we?

I certainly don't claim that any of this is easy. Some of it is easier – but I've always viewed cancer as the single hardest aspect of ageing to fix.

You've talked about enriching people's lives, but isn't it the very fact of death that gives our lives meaning?

That's nonsense. The fact is, people don't want to get sick. I'm just a practical guy. I don't want to get sick and I don't want you to get sick and that's what this is all about. I don't work on longevity, I work on keeping people healthy. The only difference between my work and the work of the whole medical profession is that I think we're in striking distance of keeping people so healthy that at 90 they'll carry on waking up in the same physical state as they were at the age of 30, and their probability of not waking up one morning will be no higher than it was at the age of 30.

You've said you think the first person to live to 1,000 may already be alive. Could that person be you?

It's conceivable that people in my age bracket, their 40s, are young enough to benefit from these therapies. I'd give it a 30% or 40% chance. But that is not why I do this – I do this because I'm interested in saving 100,000 lives a day.

Can the planet cope with people living so long?

That's to do with the balance of birth and death rates. It didn't take us too long to lower the birth rate after we more or less eliminated infant mortality 100 or 150 years ago. I don't see that it's sensible to regard the risk of a population spike as a reason not to give people the best healthcare that we can.