A new study suggests that Alzheimer’s disease develops slower in people with bigger heads, perhaps because their larger brains have more cognitive power in reserve.
It’s not certain that head size, brain size and the rate of worsening Alzheimer’s are linked. But if they are, the research findings could pave the way for individualized treatment for the disease, said study co-author Lindsay Farrer, chief of the genetics program at Boston University School of Medicine.
The ultimate goal is to catch Alzheimer’s early and use medications more effectively, Farrer said. “The prevailing view is that most of the drugs that are out there aren’t working because they’re being given to people when what’s happening in the brain is too far along,” he said.
A century ago, some scientists believed that the shape of the head held secrets to a person’s intelligence and personality — those views have been since discounted. But today, research suggests that there may be “modest correlations” between brain size and smarts. Still, “there are many other factors that are associated with intelligence,” stressed Catherine Roe, a research instructor in neurology at Washington University School of Medicine in St. Louis.
Nevertheless, there could be a connection between the size of the brain and how many neurons are available to “pick up the slack” when others go dark because of diseases such as Alzheimer’s. The new study, published in the July 13 issue of Neurology, explores that possibility.
The study authors examined the medical records of 270 patients with Alzheimer’s. They looked for links between brain shrinkage, head circumference — an indicator of brain size — and the progression of their disease.
After adjusting their results so they wouldn’t be thrown off by factors such as the age and ethnicity of the patients, the researchers found that patients with larger head sizes tended toward less brain atrophy. Also, their dementia was less advanced.
While the difference between larger-headed and smaller-headed people was significant from a statistical point of view, study co-author Farrer said it’s impossible to pinpoint exactly what the difference means in terms of how the brain works overall.
The research doesn’t confirm that brain size and the speed of the disease are directly connected. But if there is a connection, what’s going on? “One possible explanation is that larger heads, and therefore larger brains, contain more nerve cells and connections between cells,” reasoned study lead author Dr. Robert Perneczky, a researcher at the Technical University of Munich in Germany.
Therefore, he said, more brain cells have to die before “the threshold is crossed where brain damage leads to cognitive impairment and other symptoms of dementia.”
Roe, the neurology instructor, said the study appears to be valid and useful, adding that it suggests that three things are connected: brain size, the shrinking of the brain and the progression of Alzheimer’s disease.
Whatever your head size, she said, “the message is that the important thing is trying to keep your brain as healthy as possible throughout life, which hopefully will allow you to cope better with diseases like Alzheimer’s if they occur.”