"Hitting Your Head Really Hard Once May Triple Your Risk Of Parkinson's Disease" (Newsweek)

Hitting Your Head Really Hard Once May Triple Your Risk Of Parkinson's DiseaseA new paper that analyzed data from three large long-term studies has found a significant connection between head trauma with loss of consciousness and the development of Parkinson's disease later in life.DIERK SCHAEFER/FLICKR/CREATIVE COMMONS

The paper, published Monday in JAMA Neurology, pooled data from three major studies that began in the 1990s and tracked (and continue to track, for participants who are still alive) people’s brains as they age. Two of the studies reviewed data from sets of randomly chosen participants, while the third was a long-term study of priests and nuns living in orders across the country. Of these more than 7,000 participants, 1,500 have resulted in brain autopsies, which were included in the JAMA Neurology paper, making it the largest ever study on this topic. 

“That’s a massive number [of autopsies], an extraordinarily large study,” Crane says. The data is especially valuable because all three studies began before the participants developed any neurodegenerative disorders, making participants' answers to questions about prior head trauma highly reliable. (Often, Crane says, when people already have Parkinson’s disease, they are "particularly concerned with anything that might have contributed to their having Parkinson’s,” and so they may inadvertently overemphasize aspects of their health history when filling out a survey.)

The researchers found that study participants who reported having hit their head at some point in their lives and lost consciousness for an hour or more had a rate of Parkinson’s disease that was 3.5 times higher than patients who did not sustain similar head trauma.

Overall, it appeared that any head trauma that included loss of consciousness of any length of time—even less than an hour—was associated with a faster progression of “Parkinsonian features,” which is not a Parkinson's diagnosis but rather a constellation of “not so specific” symptoms that progressively get worse, such as tremors and unsteady gait. These symptoms are typically associated with Parkinson’s disease but also with a variety of other age-related diseases, like dementia, explains David Bennett, the director of the Alzheimer's Disease Center at Rush University and a co-author on the JAMA Neurology paper. 

Meanwhile, Crane expects to work on many more papers drawing from the massive data set used for this research. It isn't every day one has access to so much long-term data and so many brain autopsies, he says. "These studies exist because of the generosity of the participants, just volunteering for a study out of the goodness of their heart," he says. “Over a quarter say, yeah, you can have my brain when I die. That’s pretty remarkable.”

"We’re hoping to plumb it for many years. There’s so much we still don’t know about the aging brain."