According to researchers of University of South Florida, the size of a person's head may be one risk factor for Alzheimer's disease. People with a gene predisposing them to Alzheimer's who also have small heads were 14 times as likely to develop the disease than people without that gene variant and with larger heads.
The researchers believe people with smaller brains may be less able to compensate for the brain cell damage that is a hallmark of Alzheimer's disease, so symptoms like memory loss occur earlier in these people. But still this idea is debatable.
To test the theory, Borenstein Graves and her colleagues followed 1,700 healthy Americans age 60 or older for an average of about four years. During that time, 50 people developed Alzheimer's disease.
The researchers measured the circumference of people's heads around the eyebrows and across the widest part of the skull. According to a study, participants with the smallest head measurements were slightly more likely to develop Alzheimer's than the people with the larger heads.
People with a gene variant called alipoprotein E 4 or ApoE4, a known risk factor for the disease, were 4.8 times more likely to be diagnosed with Alzheimer's. Alzheimer's developed most often among people with the ApoE4 gene variant and a small head circumference.
According to her head circumference probably does not influence the pathology (the underlying biological damage) of Alzheimer's, but is a mitigating factor in the development of symptoms. While brain growth is controlled in part by genetics, it also may be influenced by nutrition, infection, family size, and birth order. This study is not enough to definitively link smaller head size with an increased risk of Alzheimer's.