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1. Human Longevity Roundtable Broadcast
Monday 12 March 2001 with Norman Swan
ABC Radio National Health Report http://www.abc.net.au/rn/talks/8.30/helthrpt/stories/s259079.htm
Transcript of an interview of Norman Swan with three researchers who looked at the question of how long humans can live.
S. Jay Olshansky
Professor, School of Public Health, University of Illinois, Chicago
— Estimating the upper limits to human longevity, discusses a new field of longevity research referred to as bio-demography.
Professor of Anatomy, University of California, San Francisco
— Life expectancy predictions
Professor, Danish Twin Registry, Denmark
— Human life span
Today on the Health Report I talk with some researchers who are suggesting a really radical revolution for doctors:
- They should take their patients’ pulses, comprehensively.
- Why it is truly not wise to eat and run, although an espresso might help.
- How long can humans live?
If you have believed the headlines over the last couple of years with the discovery of so-called ageing genes, you would be forgiven for thinking this generation will live for a very long time. Well, don’t get too excited about it, say some leading experts. Longevity is not what it is cranked up to be. There is too much hype and the research is not being directed at the right questions.
All this came up at a session at the American Association for the Advancement of Science meeting which took place in San Francisco in February 2001.
What we are talking about here is not so much whether the world record for longevity will continue to be broken, but what our average life expectancy is going to be. Leading the attack was Jay Olshansky Professor of Public Health, University of Illinois, Chicago.
The paper that we have is a ten year follow-up to a piece that we had published in Science in 1990; it was entitled In Search of Methuselah: Estimating the Upper Limits to Human Longevity. And in this manuscript in 1990, we had estimated that the upper practical limit to life expectancy at birth is about 85 years. Now shortly after that paper was published, a number of scientists suggested that we were too pessimistic, and that in fact they would anticipate very rapid and dramatic declines in death rates and that we could expect life expectancies of 100 years or higher at some time in the 21st century.
Well what we decided to do was, as patiently as we could, wait for ten years, to look at the first ten years worth of data, to determine whether or not changes in death rates in the longest lived sub-groups of the human population were moving in the direction that we had anticipated, or moving in a much more rapid direction, as others had anticipated.
To make a long story short, what we did basically was we looked at the mortality rates, death rates, for three long-lived populations, the United States, France and Japan, and what we had determined was that although death rates in fact were declining, and in fact declining very rapidly in Japan in particular, they were not declining at the rates required to produce these much higher life expectancies as had been predicted by other researchers. The overall conclusion that we came to was that while we anticipated that many people here today will live long enough to witness a life expectancy at birth of 85 years, what we anticipate is that everyone alive today will be long dead before a life expectancy at birth of 100 is achieved, if ever. We do not believe that there are any magical potions, hormones, anti-oxidants, forms of genetic engineering, biomedical technologies that exist today, that will permit us to increase life expectancy at birth up to 100, or even 120 or even 150, as some people have claimed.
I will address three areas of this field that I find suffer from enormous confusion and chaos in the minds of people who are not only not in this field but also newcomers to the field.
The first is to make a distinction between life expectation and life span. The human life span as far as we know has remained fixed at about 120, give or take a few years for the past 100,000 years, and that fixed point is in fact rarely addressed in any research projects that I am aware of.
On the other hand life expectation is the 50% end point that a person of a particular age will live to a subsequent later age. Life expectation at birth in this country for example, for the entire population is about 76 years, which means that 50% of the population born today will have a chance of living to the age of 76. I should also point out that I agree entirely with my colleague Dr Olshansky in respect to the outrageous claims that have been made by uninformed people in this field, however mostly out of this field, of enormous claims for super longevity in the future. It is simply not possible. One of the reasons that it is not possible is that even if you were successful in eliminating all causes of death currently written on the death certificates of people in the G7 countries, the increase in life expectation would be no more than 15 years. You would then reveal the true cause of the increased vulnerability to those diseases in old age, namely the ageing process, a process that strangely enough is rarely studied.
The second point that I intend to make has to do with a critical distinction that must be made between ageing and longevity determination. Longevity determination occurs as a result of the redundant physiological capacity that virtually all animals have at the time of sexual maturation, and that has occurred as a result of natural selection in which greater physiological capacity has been provided in order to better assure that individual members of a species will reach sexual maturation and therefore guarantee the survival of the species.
So that in humans, for example, at the age of 20 roughly, we have far more physiological capacity than we need, but that has occurred as a result of natural selection in order to better guarantee that a greater number of people reach that age. After that period of time that greater physiological capacity permits us to coast, if you will, or freewheel, for an additional four or five decades, and that is the indirect determination of longevity. It is the same thing that you appreciate when you drive your Mercedes Benz off the showroom floor and realise that it better not come back to the repair shop in eight or ten years because of your faith in its construction, design and workmanship. Whereas my Ugo driven off the showroom floor has a completely different set of anticipations. That is the difference between longevity determination, which is a critical concept, and the ageing process which is a random stochastic process that occurs, in humans for example and most other animals, after a reproductive success.
And the final point that I want to make is that ageing must be distinguished from disease because it is essential to understand that virtually all of the research done under the rubric of ageing research is in fact research on diseases of old age, the resolution of which as I pointed out earlier, will not provide a mortality to all of us, it will provide for example, in the case of the resolution of cancer as a cause of death in this country and other G7 countries, an additional 2-1/2 years of life expectation; cardiovascular disease, the leading cause of death in this country, approximately 12 years of additional life expectation. Ageing on the other hand, in respect to studying the process, does have the potential to allow us additional longevity, but there are relatively few people working on this subject in humans, and I think the likelihood of that occurring certainly in my lifetime and the lifetime of my children and grandchildren, is about as close to zero as you can get.
The fundamental question is this: why are old cells more vulnerable to pathology than young cells? That is the question, and that you will find rarely addressed in this field. What are addressed in this field (because it sells) are the diseases of old age. Nobody thinks that they are going to die (these days at least) of old age; they think people are going to die either of cancer, cardiovascular disease or stroke. That is the limit of the freedom of choice in respect to how you will die. And as a consequence of that, that is an easy sell to Congress, to politicians, and to decision-makers, and especially to the medical community, which reaps enormous benefit from this position.
But the fact is that in Australia at the beginning of the 20th century, a baby girl would have had a life expectancy of around 50, whereas 100 years later, a newborn girl can expect to live to over 80.
That is an incredible change and you can see why the optimists think the possibilities are endless, especially when statistics from, say, Scandinavia make people like Professor Kaare Christenson of the Danish Twin Registry, reckon the party is far from over.
The death rate for the oldest old has been cut into half from 1950 to now, meaning being an 80-year-old woman is only half as dangerous today as it was 50 years ago. And there is no evidence that this is slowing down, and the countries that already have the highest life expectancies are experiencing the biggest improvement. If it was so that these countries were pushing up against the limit, you should expect the progress to kind of slow down approaching the limit. However the countries that have the longest life expectancies are making the biggest progress.
Also if you look at the population of centenarians, it is about doubling every ten years, and a record life span in any year for the last 150 years has been steadily increasing, and speed in the record-breaking is on the increase, not on the decrease.
Professor Kaare Christenson reckons we have not come close to the limits of human life span. But does not that contradict the skepticism from researchers like Leonard Hayflick?
I agree completely with my colleague’s statements about the increase in life expectation, but 21 of the 27 year increase in life expectation that occurred during the 20th century took place in the first 70 years. Only a six year increase in life expectation occurred in the past 27 years, so that if you have your point of origin within the last 27 years, certainly it is an upward slope, and it will continue to slope upwards; this is not a question of there not being an increase, it is a question of the slope of the curve.
What they are talking about here is the effect on the statistics of changing life expectancy at different ages. The reason life expectancy increased so much in the first half of the 20th century was that deaths in infancy and childhood were prevented.
But if you actually survived childhood and reached the age of 60 in 1950, and compared yourself to someone who reached the age of 60 in 1900, your chances of getting to 80 in 1950 had not increased much in that half-century. They stayed roughly the same.
And that is exactly where the extra life expectancies come from in the last few decades: if you get to 60 these days, you can expect to live a fair bit longer than your grandparents did at that age.
But coming back to that statistic, overall life expectancy at birth: when you prevent a childhood disease, a fatal one, the number of years added to your life is enormous. Whereas if you delay death at 60, the number of years gained are inevitably much fewer. That means even though the limit of life expectancy has not been reached, we are approaching it more slowly.
So despite legitimate optimism, the predictions are that life expectancy will, by 2075, only be around 88 years in countries like Australia.
Has not the genetic revolution discovered all these genes which can increase the life span of fruit flies and worms, and is not that going to translate into longer lives for humans?
No, because genes have absolutely nothing to do with ageing. If you substitute the word “ageing” and describe that work as “longevity determination”, you would have a better picture of what was discovered at that time. The folks who have allegedly identified genes for ageing have, in fact, identified genes that are involved in the physiological processes that go towards increasing longevity of their particular animal subjects. They were not studying the human ageing phenomenon because at that point in time experiments on the ageing process had not begun—even in worms and flies. Furthermore, there is no need for a gene for ageing for the same reason that the blueprint that was used to design your Mercedes does not contain a feature to cause it to age. There is no need for it.
We can fall apart without the help of our genes! So, how long do these ageing researchers themselves want to live?
How long do I want to live? I think fundamentally that is the wrong question to ask. I do not care how long I live, quite frankly. What I care about and what I think we should be caring about is we should be much more focused on enhancing the quality of the days that we have. We seem to be enthralled with this idea of making ourselves live longer and longer, and pushing out the envelope of human survival. What is really important is not how long we live, but how healthy we are along the way.
So, my answer to that question is I do not care, as long as I am healthy for as long as possible, during the time in which I am alive.
Olshansky S.J. et al. In Search of Methuselah: Estimating the Upper Limits to Human Longevity, Science 250, 634 (1990).
Olshansky S.J. et al. Prospects for Human Longevity, Science , 291 (5508: 1491), 23 February 2001.
Story Index http://www.abc.net.au/rn/talks/8.30/helthrpt/index/index.htm
2. Peering inside the wandering mind
ScienceNow News Broadcast, 18 January 2007
Scans through different sections of the brain show neural activity correlated with mind wandering.
Credit: M. Mason et al, ScienceNow
One moment you are paying close attention to a lecture, the next you are making a mental list of items you need to pick up at the store and wondering who will be at the party on Saturday night. Minds wander and now a study sheds new light on what happens in the brain when thoughts go astray.
The researchers, led by cognitive psychologist Malia Mason, currently a postdoctoral fellow at Harvard Medical School in Boston, began by asking 19 volunteers to perform simple recall tasks such as memorizing a short string of letters and reproducing them in forward or reverse order. Reasoning that minds wander more when the job at hand is not very demanding, the researchers had the volunteers practice the tasks for 30 minutes on three consecutive days. During a fourth practice session, the researchers butted in to ask the subjects whether they were having stray thoughts. As expected, they reported more random thoughts when working on a familiar sequence than when grappling with a novel one.
On the fifth day of the experiment, volunteers slid into a functional magnetic resonance imaging (fMRI) scanner. The scans revealed that a particular set of interconnected brain regions was more active when volunteers worked on well-practiced sequences and in individuals who had reported a greater tendency for mental wandering. Mason and colleagues report their findings in the 19 January issue of Science.
In 2001, neurologist Marcus Raichle of Washington University in St. Louis, Missouri, and colleagues noted that the same set of brain regions buzzes with activity when people are not concentrating on any particular task. Raichle called it the "default network." He says that the new work suggests that activity in the default network is necessary to generate spontaneous thoughts and adds to evidence that it makes an important contribution to our inner life. In one published case study, Raichle notes, a woman who suffered damage to part of the default network initiated almost no spontaneous thoughts. "Her mind was empty," Raichle says.
The study leaves open the question of why minds wander, says Jonathan Schooler, a psychologist at the University of British Columbia in Vancouver, Canada.
Schooler suspects that mental rambling is generally beneficial. "A lot of the time people are thinking about worries or problems that they need to work out," adding that creative insights often happen during these episodes. The new study could be a big help to researchers if it leads to a way to use fMRI to detect mind wandering without interrupting an experimental subject.”
Greg Miller, ScienceNOW Daily News, broadcast on 18 January 2007. http://sciencenow.sciencemag.org/cgi/content/full/2007/118/1
3. When Your Brain Goes Shopping
Science NOW , News Broadcast, 4 January 2007
The brain weighs the pleasure of a purchase against the pain of losing money, a study suggests.
Credit: Jack Hollingsworth / Photodisc Green
That new iPod looks terrific ... but $249 is a lot of money. To buy or not to buy? A new study sheds light on how our inner consumer makes such existential choices.
Observers of human behaviour have long wondered what motivates people when they shop. Some theories say that shoppers weigh the anticipated pleasure of a purchase against the inevitable "pain" of parting with some of their money, while others have suggested that people weigh the benefits of a purchase against the benefit of buying something else. "It is sort of good-versus-bad, or good-versus-good," says Stanford neuroscientist Brian Knutson.
So Knutson, along with colleagues from the Massachusetts Institute of Technology in Cambridge and Carnegie Mellon University in Pittsburgh, Pennsylvania, had 26 volunteers make a series of rapid purchasing decisions with their heads inside an fMRI-scanner.
On a screen, the subjects were shown a series of attractive products, such as an MP3-player, a Sex and the City DVD, a box of Godiva chocolates, or a Stanford T-shirt. To simulate a real store, the subjects first saw the item alone for a few seconds, then the price, after which they had to choose: Buy it or not? To get them into a buying mood, each was given store credit; and to make the stakes more real—without bankrupting the lab—participants actually got to keep a few of their purchases. After the scan, they were asked how much they liked each product, and what they would be willing to spend on it.
The researchers found that when subjects liked a product, the region in their brain called the nucleus accumbens—a part of the striatum, which had previously been associated with the anticipation of gains—was activated. On the other hand, when they judged the price of an article as too expensive, a region called the insula was activated while another called the mesial prefrontal cortex was deactivated—two phenomena previous studies have linked to the anticipation of loss and pain. Together, the findings provide evidence for the "good-versus-bad" theory, says Knutson.
Neuroscientist Alain Dagher agrees. "It is a very simple and very elegant study," says the Montreal Neurological Institute researcher, who wrote a commentary that appeared alongside the paper itself in today's issue of Neuron. Although pushing buttons in a lab is not quite the same as visiting Macy's, he says, "Knutson’s research team really tried to simulate the shopping experience while people were lying in the magnet."
However, Dagher points out that the nucleus accumbens has also been implicated in addictions, so a logical next step would be to see if people with addictive shopping behaviour have different activation patterns than do others.
Project Manager and Editor, Quality4life
24 January 2007