Sunday, November 21, 2010

Backlash against genetic explanation for longevity

The criticisms seem to be of the nitpicking variety -- and likely to be insubstantial in view of the fact that the authors in the original study took care to cross-validate their conclusions. They showed that the set of characteristics that they found in their first group had predictive power on a totally different second body of people.

I think that the criticisms are principally motivated by the usual Leftist hatred of genetic explanations generally. They would like you to think that avoiding so-called "junk" foods was the path to longevity -- despite there being no double-blind evidence of that

I can't resist pointing out again that we Australians have exceptionally long life spans -- with lots of nonagenarians tottering around the place who grew up on a traditional diet of fried steak and onions -- fried in dripping (animal fat) and with plenty of salt for flavouring. I think that falsifies food-freak assertions pretty convincingly. It certainly was not a low fat or low salt diet that got so many of our oldies into their 90s. Most families I know here in Australia have or have had a nonagenarian somewhere among their relatives -- my own family included, even a centenarian in my case

Researchers had claimed by studying genomes it was possible to predict a person’s lifespan with an accuracy of 77 per cent. They said people carrying certain longevity genes would be likely to live beyond 100, regardless of their lifestyle.

The study opened up the possibility of screening people for life threatening diseases who were deemed to be at risk of early death.

Scientists at Boston University found the “genetic signatures of exceptional longevity” by studying more than 1,000 people who had lived beyond 100.

But now other scientists have expressed technical doubts about the way the researchers arrived at their main conclusions. Researchers involved in similar studies where entire genomes are scanned by sophisticated “gene chips” said one of the chips could produce “skewed data” under certain conditions.

The Journal Science, which published the study earlier this year, has issued an unprecedented “editorial expression of concern”.

It is unlikely that the study will be retracted but some of the results may be revised following fresh analysis of the data.

When the initial study was published, one of the authors, Doctor Thomas Perls, said: "These genetic signatures are a new advance towards personalised genomics and predictive medicine, where this analytic method may prove to be generally useful in prevention and screening of numerous diseases, as well as the tailored uses of medications."

His co-author Professor Paola Sebastiani said the preliminary data suggest that exceptional longevity may be the result of a "defensive genes" that counter the effect of disease-associated damage to the body and contribute to the compression of morbidity and disability towards the end of these very long lives.

But Prof Sebastiani added: "This prediction is not perfect, however, and although it may improve with better knowledge of the variations in the human genome, its limitations confirm that environmental factors – for example, lifestyle – also contribute in important ways to the ability of humans to survive to very old ages."


Night lights 'could cause depression'

If you are a Siberian hamster. Primitive people must have been depressed a lot -- with that pesky moon shining down on them such a lot. Anybody want to guess that human beings are fully adapted to that?

Sleeping in anything other than a completely dark room could lead to depression, research suggests. Neuroscientists believe that even having a dim light on - such as a night light often used in a child's room - adversely affects the chemical balance and structure of the brain. Such a light appears to interfere with secretion of the hormone melatonin, which helps let the body know it is night time.

A team at Ohio State University in the US came to their conclusions after comparing two sets of Siberian hamsters, one group which was exposed to a dim light at night, the other which enjoyed complete darkness.

Tracy Bedrosian, a doctoral student who co-authored the study, said: "Even dim light at night is sufficient to provoke depressive-like behaviours in hamsters, which may be explained by the changes we saw in their brains after eight weeks of exposure." For example, she said they drank less sugar water.

When they examined the hamsters' brains they found those exposed to dim night light had less dense networks of dendritic spines in a part of the brain called the hippocampus. Dendritic spines are the hairlike growths on brain cells that transmit chemical messages from one cell to another.

Bedrosian, who presented the research on Wednesday at the annual meeting of the American Society for Neuroscience in San Diego, added: "The hippocampus plays a key role in depressive disorders, so finding changes there is significant."

Earlier studies in mice have found that those exposed to bright light at night tend to become depressed and put on weight.


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