A new study suggests that irregular arm swings while walking could be an early sign of Parkinson's disease, an age-related disorder involving loss of certain types of brain cells and marked by impaired movement and slow speech.
According to researchers, early detection could help physicians apply treatments to slow further brain cell damage until strategies to slow disease progression are available.
"The disease is currently diagnosed by tremors at rest and stiffness in the body and limbs. But by the time we diagnose the disease, about 50 to 80 percent of the critical cells called dopamine neurons are already dead," said Xuemei Huang, associate professor of neurology, Penn State Hershey College of Medicine.
Huang and her colleagues are studying gait, or the manner in which people walk, to understand the physical signs that might be a very early marker for the onset of Parkinson's.
They have confirmed Huang's clinical impression that in people with Parkinson's, the arm swing is asymmetrical. In other words, one arm swings much less than the other as a person walks.
"We know that Parkinson's patients lose their arm swing even very early in the disease but nobody had looked using a scientifically measured approach to see if the loss was asymmetrical or when this asymmetry first showed up. Our hypothesis is that because Parkinson's is an asymmetrical disease, the arm swing on one arm will be lost first compared to the other," said Huang.
The researchers compared the arm swing of 12 people diagnosed three years earlier with Parkinson's, to eight people in a control group.
Analysis of the magnitude of arm swing, asymmetry and walking speed revealed that the arm swing of people with Parkinson's has remarkably greater asymmetry than people in the control group, one arm swung significantly less than the other in the Parkinson's patients.
When the participants walked at a faster speed, the arm swing increased but the corresponding asymmetry between them remained the same.
"We believe this is the first demonstration that asymmetrical arm swings may be a very early sign of the disease," said Huang.
The findings appear in the current issue of Gait and Posture.