Alzheimer's 'link' to small heads

Memory loss is an early sign of dementia

People who have small heads, plus a key gene variant, are at increased risk of developing Alzheimer's Disease, an American scientist has claimed.

But UK experts say the research is flawed and its findings do not stand up.

Dr Amy Borenstein Graves, of the University of South Florida in Tampa, suggests a head circumference of less than 21.4 inches puts people at greater risk.

However, they also have to have the e4 variation of the ApoE gene, which produces a protein that helps control levels of fats in the blood.

Small head size alone does not increase the risk, she said.

This is not particularly helpful research

Dr Richard Harvey, Alzheimer's Society

Dr Borenstein Graves said people with both risk factors are 14 times more likely to develop Alzheimer's.

She added that in her study, 18% of the risk of Alzheimer's was "directly attributable to small head size."

Dr Richard Harvey, of the UK's Alzheimer's Society, said measuring head circumference was unreliable and studies measuring the size of the space within the skull through scans had found no difference between people who had had Alzheimer's and those who did not.

Alzheimer's disease is the most common cause of dementia, which typically begins with memory lapses.

Head size link

The US research is published in Neurology, the journal of the American Academy of Neurology.

The study followed 1,869 healthy Japanese Americans who were 65 or over for just under four years.

Information about whether they had the key gene was only available for 59% of those involved.

Only those with both a head circumference of less than 21.4 inches and the ApoE e4 gene were at greater risk of Alzheimer's.

Dr Richard Harvey : 'Sceptical' about the head circumference link

Those who developed the disease were also older, less educated, shorter, lighter and had a lower estimated verbal IQ, than those who did not.

Dr Borenstein Graves said the study added weight to the theory having a large brain protects against Alzheimer's.

She said: "The theory is that the symptoms appear when the loss of brain cells goes below a critical threshold.

"People with ApoE e4 are likely to have more rapid brain cell damage.

"Those with large brains may have the same changes in the brains, but they don't show symptoms of the disease until much later."

She said it may be possible to retain more brain cells by preventing the brain damage that occurs during a person's lifetime.

Dr Borenstein Graves said while genetics played a part in brain growth, it was also influenced in childhood by factors such as malnutrition, poverty, infection and birth order.

Later in life, factors such as higher education, income and mental and physical exercise could play a part, she said.

"It is interesting to speculate on whether we could prevent this disease if we could systematically boost our brain reserves throughout life.

"If it were possible to increase brain reserve through prevention of brain damage that occurs throughout the life span, nearly 20% of the disease among these individuals might be presentable."

Limitations

Dr Borenstein Graves admitted that the impact of the study was limited because the work had been done in the Japanese American population, but she said her findings had been confirmed in other populations.

However, Dr Harvey said he was "sceptical" about the research.

He said even the basic measuring of circumference was difficult to do accurately.

"If you have to measure the circumference of people's heads and someone else did it, they are likely to get a different measurement."

Dr Harvey said the fact that information on the ApoE e4 was only available for 59% of the study group also cast doubt on the researcher's findings.

He said Dr Graves had done a similar piece of work with the same population five years ago.

"This is not particularly helpful research."