ASEL, Switzerland, Feb. 7 -- Patients who've used calcium channel blockers long term to treat hypertension got a small bonus in the form of Parkinson's disease protection, an observational study found. Action Points
Explain to interested patients that patients who had been taking calcium channel blockers for at least several years had a reduced risk of developing Parkinson's disease.
Explain that other hypertension medications did not appear to have the same effect.
The risk was lowered 23% compared with Parkinson's patients who didn't take the drugs, Christoph R. Meier, Ph.D., of University Hospital Basel, and colleagues reported online in the Feb. 6 issue of Neurology.
On the other hand, this large primary care-based case-control study found no benefit for people taking angiotensin converting enzyme (ACE) inhibitors, angiotensin II (AT II) antagonists, or beta-blockers, the researchers reported.
In search of neuroprotective agents that may help play a role in Parkinson's disease, recent studies have found promising results for ACE inhibitors and calcium channel blockers in animal studies and in a small pilot study with an ACE inhibitor, the researchers wrote.
To explore the association between antihypertensive drug use and the risk of developing a first-time diagnosis of Parkinson's disease, the researchers undertook a case-control analysis within the United Kingdom's General Practice Research Database.
The study included 7,374 men and women 40 or older. Half the group (3,637 individuals) had incident idiopathic Parkinson's disease diagnosed from 1994 to 2005. Approximately 90% of the individuals were diagnosed after the age of 60.
An equal number of controls without Parkinson's were matched to each Parkinson's patient for age, sex, general practice, index date, and duration of previous history in the database.
Among the Parkinson's cases, 1,704 (46.9%) had used an antihypertensive drug before the index date. Of these, 629 (17.3%) had used an ACE inhibitor, 89 (2.5%) an AT II antagonist, 1,168 (32.1%) a beta-blocker, and 807 (22.2%) a calcium channel blocker. Some patients took more than one drug, the researchers noted.
Odds ratios were calculated with conditional logistic regression, adjusted for body mass index, smoking, and various cardiovascular, metabolic, and psychiatric diseases and dementia.
Compared with Parkinson's patients who did not use hypertension medication, the adjusted OR for current use and a history of 30 or more prescriptions for the drug was 1.08 (95% CI 0.85 to 1.37) for ACE inhibitors, 0.91 (95% CI 0.41 to 2.00) for AT II antagonists, and 1.16 (95% CI 0.95 to 1.41) for beta-blockers.
This compared with an OR of 0.77 (95% CI 0.63 to 0.95) for calcium channel blockers -- or a 23% reduction in risk.
Thus, the researchers said, current long-term use of calcium channel blockers was associated with a reduced risk of Parkinson's disease, while the risk was not materially altered for users of ACE inhibitors or beta-blockers and, with less statistical precision, for users of angiotensin II antagonists.
The finding that calcium channel blockers may "slightly reduce" the risk of developing Parkinson's disease came from an analysis comparing calcium channel blockers with other antihypertensive drugs, and one with nonusers of any hypertensive medication.
There was a tendency toward a stronger risk reduction in women with current long-standing use than in men, but not for those with fewer than 30 prescriptions. In addition, the risk reduction was most pronounced in individuals 80 or older.
This finding is interesting the researchers said, in light of a recent article suggesting that, with advancing age, dopaminergic neurons rely increasingly on calcium channels for their activity, which would make them more vulnerable to neurologic damage.
By contrast, neurons of younger people use different mechanisms. If these calcium channels are blocked, neurons again make use of these less harmful mechanisms and cell damage may be decreased, the researchers said.
Study limitations included the fact that the researchers could not adjust for level of education, socioeconomic status, or cholesterol levels, which may have been associated with Parkinson's disease.
As in other epidemiologic studies, the index date for the onset of Parkinson's was difficult to define accurately, although the investigators said they undertook various measures to control for possible confounders.
Furthermore, they said the findings cannot be distorted by recall bias since all drug use was recorded before the Parkinson's diagnosis.
In an interview, Dr. Meier said that more research is needed to determine why calcium channel blockers appear to protect against Parkinson's disease, whether the association is causal, and why the other hypertension medications did not reduce the risk.
