Memory loss linked to weight gain

Women who hope to preserve their memory as they grow older may want to consider shedding some excess pounds.

That’s because researchers at Northwestern University in Chicago have found a link between memory loss and weight gain in older women. Simply put, the more an older woman weighs, the worse her memory, according to the study published this week in the Journal of the American Geriatric Society.

The findings are based on 8,745 post-menopausal women, aged 65 to 79, who took a 100-point memory test. The score for normal memory is in the 90- to 100-point range. After completing the test, the score for each woman was matched to her Body Mass Index, or BMI.

It’s a standardize measure based on weight and height.

The study revealed that for every one point increase in a woman’s BMI, her memory score dropped by one point. “Any excess fat appears to be detrimental,” said Diana Kerwin, the lead author of the study.

Previous research has shown that other conditions, including high blood pressure, elevated cholesterol levels and diabetes, can affect blood flow to the brain and impair cognitive function. These medical conditions often go along with being overweight. However, even when those conditions are not present, excess weight was still tied to reduced memory among the study participants. That suggests weight, by itself, is an independent risk factor for memory loss.

Furthermore, the researchers found that some types of fat – and where it’s located – seem to be worse than others. For instance, “pear-shaped” women, who tend to pack the pounds on their hips and thighs, suffered more memory impairment than their “apple-shaped” counterparts who accumulate fat around their bellies.

Dr. Kerwin said admits she was surprised by this particular discovery because other studies have indicated that it’s normally better to have a pear-shape than an apple-shape. When fat builds up around the abdomen – the traditional apple shape – it usually increases the risk of heart disease, type 2 diabetes and some cancers. “We have quite a lot to figure out,” she said, referring to the unexpected findings related to pear and apple physiques.

Even so, Dr, Kerwin said researchers already have a few clues worth following. She noted that different types of fat release different cytokines and hormones that regulate a wide range of bodily functions. Abdominal fat, for instance, produces low levels of estrogen – which may minimize the overall negative effect of fat on older women whose ovaries are no longer producing a steady stream of the female hormone.

By studying these various substances and their specific effects on the body, researchers should gain a better understanding of how fat affects memory, said Dr. Kerwin. She added that she is already making plans to do this type of study.

Nature’s speed limit

It seems that mother nature has imposed a speed limit on how fast messages travel along nerves, and that may help explain why elephants have a lumbering gait, while mice are so fast on their feet.

Researchers at Simon Fraser University in British Columbia measured the nerve speed of a variety of mammals, ranging from elephants to shrews. They found that nerves of all the animal tested, regardless of size, conducted impulses at roughly the same speed – about 50 metres a second. That essentially means large animals are going to have a delayed reaction time compared with small creatures, because they have to transmit nerve data over much longer distances. (Think how hard it would be to catch mice in the wild with your bare hands. You may be big, but they’re nibble.)

The senior author of the paper, Max Donelan, said it’s theoretically possible for large animals to exceed the nerve speed limit – but they would require much thicker nerves. In order to have the same reaction time and sensory perception as a tiny shrew, the elephant would need, for example, a sciatic nerve with a diameter of 30 metres, said Dr. Donelan. Of course, that would be impractical.

But what they lack in speed and agility, bigger beasts the big fellows tend to compensate with increased brain power. Indeed, Dr. Donelan, whose study was published in the Proceedings of the Royal Society B, thinks the nerve speed limit may have driven large animals to become smarter. “Large animals need to think ahead and predict any changes that will occur so they have time to adapt their movements according,” he explained.

“It could be that the nervous systems of large animals evolved to become excellent predictive machines. A brain that is good at predicting movement may also become good at predicting other aspects of life,” added Dr. Donelan, who believes such forces also had a role to play in the evolution of the human brain. After all, it takes a smart person to invent a better mouse trap.

The Sunshine vitamin

Vitamin D appears to play a critical role in maintaining a healthy, well-functioning brain, two new studies indicate.

One study, involving Finish///Finnish volunteers, found that people with abnormally low levels of the nutrient were at an elevated risk of developing Parkinson’s disease, a neurological condition that results from the death of brain cells governing movement. The findings were published in Archives of Neurology.

The second study, focusing on Italian participants, revealed that older people with a severe vitamin D deficiency were more likely to have problems with memory, learning and thinking. The results appeared in Archives of Internal Medicine.

The studies, which were both released this week, add to a growing body of research that suggests vitamin D plays a much larger part in overall health than once imaged.

The vitamin is made naturally in the body when skin is exposed to sunlight. But many people have low levels of the “Sunshine vitamin” because the sun’s rays are just too weak in fall and winter to produce the nutrient. Furthermore, as people grow older, their skin becomes less efficient at making vitamin D.

“It’s estimated that one-billion people worldwide have insufficient levels of vitamin D, so this is a real cause for concern,” said the lead author of the Italian study, David Llewellyn of Exeter University in Britain.

What’s now needed, he said, is a large clinical trial to see if popping vitamin D supplements can help prevent cognitive decline in the elderly.

courtesy of the globe