"There are not necessarily direct clinical implications, but the data support previous hypotheses that calcium channel blockers may have neuroprotective effects," said study senior author Christoph R. Meier, a clinical pharmacologist with University Hospital Basel, in Switzerland. "This may stimulate additional clinical and mainly basic research in this area."
The findings were published in the Feb. 6 online issue of Neurology, the medical journal of the American Academy of Neurology.
Parkinson's disease is a chronic, degenerative neurological disorder affecting at least one million people in the United States and six million people worldwide, according to the Michael J. Fox Foundation for Parkinson's Research. The condition involves the loss of brain cells that produce the chemical dopamine, resulting in movement problems including tremors.
Previous studies with rodents and primates had uncovered a possible "neuroprotective effect" from calcium channel blockers and angiotensin converting enzyme (ACE) inhibitors, another class of blood pressure medications, the researchers said.
The new study looked at the effect of calcium channel blockers, ACE inhibitors, AT II antagonists and beta blockers on the development of Parkinson's disease.
The study involved more than 7,000 men and women in the United Kingdom over the age of 40, half of whom had been diagnosed with Parkinson's and half of whom had not. Almost half the people in each group used blood pressure medications.
Participants currently taking calcium channel blockers lowered their risk of developing Parkinson's by 23 percent. There was no real effect for the other types of medications.
The strongest reduction in risk was seen in patients who had had 30 or more prescriptions filled and were still receiving prescriptions within 90 days prior to the diagnosis of Parkinson's, the researchers said.
Women tended to have more of a risk reduction than men but not if they had had less than 30 prescriptions filled. Individuals over the age of 80 had the most pronounced lowering of risk.
But even the study authors acknowledged that it's not clear where to go next with the findings.
"It may be desirable that basic research activities explore the effect of calcium channel blockers on the central nervous system which may lead (in theory) to new therapeutic strategies or even new drugs to prevent or treat Parkinson's," Meier said. "Regarding clinical or epidemiological/observational research, it would be nice if other research groups analyzed their databases and came up with their findings. They may either confirm our observations or come to the conclusion that our finding is isolated and that there is no need to further pursue this issue."
Dr. Ralph Sacco, professor and chair of neurology at the University of Miami Miller School of Medicine, agreed. "This is a tricky one. You don't know if there is a true association or not. There are potential problems with this type of analysis," he said.
But, Sacco pointed out, there is evidence accumulating on the relationship between Alzheimer's, another neurodegenerative disease, and circulatory system problems.