Overweight elderly 'live longer'

Moderately overweight elderly people may live longer than those of normal weight, an Australian study suggests.

But being very overweight or being underweight shortened lives.

The report, which was published in the Journal of the American Geriatric Society, said dieting may not be beneficial in this age group.

But the study of 9,200 over-70s also found that regardless of weight, sedentary lifestyles shortened lives, particularly for women.

The study by the University of Western Australia set out to find out what level of body mass index (BMI) was associated with the lowest risk of death in the elderly.

For younger people, there is a well established health risk from being overweight or obese.

Overweight best

The team tracked the number of deaths over 10 years among volunteers who were aged 70 - 75 at the start of the study.

It found that those with a BMI which classed them as overweight not only had the lowest overall risk of dying, they also had the lowest risk of dying from specific diseases: cardiovascular disease, cancer and chronic respiratory disease.

The overall death rate among the obese group was similar to that among those of normal weight.

But those who were very obese had a greater risk of dying during the 10 year period.

Lead researcher, Professor Leon Flicker said: "Concerns have been raised about encouraging apparently overweight older people to lose weight.

"Our study suggests that those people who survive to age 70 in reasonable health have a different set of risks and benefits associated with the amount of body fat to younger people."

The conclusion of this study, that being overweight may be less harmful for elderly people, corroborates the findings of previous research.

Staying still

Sedentary lifestyles shortened lives across all weight groups, doubling the risk of mortality for women over the period studied, and increasing it by 25% for men.

Physical exercise "really matters", said Professor Flicker.

As well as helping to build muscle mass, it has broader health benefits for elderly people, he said.

The authors believe BMI may give a poor reflection of fatty mass in elderly people.

"It may be time to review the BMI classification for older adults," says Professor Flicker.

Professor Kay-Tee Khaw from Cambridge University agreed, noting that optimal weight appears to be higher in older age groups.

"This is important since under-nutrition is an important problem in older people.

"Waist circumference, which assesses abdominal obesity, appears to be a better indicator of health consequences of obesity" she said.

Prions 'may keep nerves healthy'

Experiments on mice may help scientists understand the workings of the prion protein linked to brain disease vCJD.

Swiss researchers say there is evidence that prions play a vital role in the maintenance of the sheath surrounding our nerves.

They say it is possible that an absence of prions causes diseases of the peripheral nervous system.

One expert said there was growing evidence that the prion had a number of important roles in the body.

As well as the latest research in the journal Nature Neuroscience, other studies have indicated prions may protect us from Alzheimer's disease or even play a role in our sense of smell.

The prion protein only came to the attention of scientists in recent years as they searched for the cause of vCJD - the human variant of BSE, or Mad Cow Disease.

This degenerative and incurable brain condition is now thought to be caused by a "mis-folded" version of the prion.

However, there is still little understanding of what the protein is supposed to do in its normal, healthy, form.

Healthy prions

The study, by scientists at the University Hospital in Zurich, looked at mice bred with fewer prion proteins.

While these mice are known to be resistant to prion diseases equivalent to vCJD in humans, they showed a number of abnormalities, including a degeneration, later in life, of the peripheral nerve cells, and the protective myelin sheath which surrounds them.

Peripheral nerves are those which link the limbs and organs to the central nervous system - the spinal cord and brain.

Looking more closely, researchers examined the effects of removing the prion protein in both the nerve cells themselves, and the Schwann cells surrounding them, which are responsible for making the myelin sheath.

While removing protein from the Schwann cells had no effect, taking it from the neurons led to a breakdown of the myelin and degeneration of the nerve cells.

They said that the knowledge that prion protein played some role in the healthy upkeep of nerve cells could offer a new avenue of research into diseases affecting humans.

However, scientists caution that it is too early to pick out a particular peripheral nerve condition which might correspond to the mouse experiments.

Recent work

Professor Nigel Hooper, from the University of Leeds, agreed that the role of the protein was not well understood.

His own work, published in 2007, suggested that it might offer some protection from the development of Alzheimer's disease.

But he said this was unlikely to be the complete answer.

He said: "Most people started by focusing on prions in relation to a human disease, and have only recently started to examine what it normally does.

"There is some evidence that it could have a number of different roles, depending on its whereabouts in the body - a recent paper linked it to olfaction or the sense of smell."