Methamphetamine Abuse May Raise Risk for Parkinson's Disease

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Methamphetamine Abuse May Raise Risk for Parkinson's Disease

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September 3, 2010 — Heavy methamphetamine users have a higher than

normal risk of developing Parkinson's disease (PD), a new study suggests.

Compared with patients hospitalized for another medical diagnosis,

appendicitis, those hospitalized for methamphetamine abuse or dependence

had a greater than 2-fold increase in PD risk during follow-up.

" We strongly emphasize the preliminary nature of the findings, "

J. Kish, PhD, from the Centre for Addiction and Mental Health, Toronto,

Ontario, Canada, and colleagues note in their report. Nevertheless, they

say, the data, " provide some evidence that exposure to methamphetamine

of a severity sufficient to contribute to hospital admission might be

associated with increased risk of Parkinson's disease. "

The study findings were published online August 24 in the journal

Movement Disorders.

Public Health Concern

Worldwide, it is estimated that 16 million people use methamphetamine,

the study authors note. Findings in animals that exposure to the illicit

drug can damage brain dopamine neurons " raise the public health concern "

that methamphetamine might also damage dopamine neurons in humans,

leading to parkinsonism, they write.

To investigate, Dr. Kish and colleagues identified 1863 methamphetamine

users, 50 years or older, who were hospitalized in California for a

methamphetamine-related condition from July 1, 1990, to June 30, 2000,

and were followed up for up to 10 years after discharge.

Roughly 87% of these individuals received a single International

Classification of Diseases, Ninth Revision (ICD-9) diagnostic code for

either methamphetamine abuse or methamphetamine dependence. The

methamphetamine users were matched on demographic variables and

follow-up time to 9315 patients hospitalized for primary appendicitis

conditions.

In regression analysis, compared with the appendicitis group, the

methamphetamine group was at significantly greater risk of being

hospitalized with PD during follow-up. The adjusted hazard ratio was

2.65 (95% confidence interval, 1.17 – 5.98, P = .019).

Reached for comment, Tomas R. Guilarte, PhD, who was not involved in the

study, said that " it's important to look at this issue because

methamphetamine targets the dopaminergic presynaptic neurons and there

is clearly injury to these neurons.

" It is certainly possible that this could modify progression of a

disease in a person that has a propensity to develop Parkinson's

disease, " added Dr. Guilarte, who is a professor of neurotoxicology and

molecular imaging in the Department of Environmental Health Sciences at

s Hopkins Bloomberg School of Public Health in Baltimore, land.

Limitations, Caveats

In their article, Dr. Kish and colleagues point to several limitations

of the study, chief among them the small sample size limited to hospital

admission cases and the uncertainty of whether the hospital diagnosis of

PD was confirmed by a neurologist. They also did not have

neuropathological data to confirm the diagnosis of PD, and ICD-9 codes

do not distinguish between methamphetamine and other amphetamines.

On the other hand, for a variety of reasons, the current study, Dr. Kish

and colleagues say, could have underestimated the actual association

between methamphetamine use and incident PD.

For instance, methamphetamine users may have been more likely to die

during follow-up and less likely to have health insurance, resulting in

less access to medical care, compared with the appendicitis group — 2

factors that may have attenuated the incidence rate of PD among

methamphetamine users.

In addition, studies have consistently shown that tobacco smoking is

associated with a lower incidence of PD. Given that methamphetamine

users typically have higher rates of tobacco use relative to the general

population, it's possible that the link between methamphetamine use and

PD is stronger than that observed in the current study, Dr. Kish and

colleagues note.

More Study Warranted

Dr. Guilarte told Medscape Medical News, " Dr. Kish is a careful

researcher and this is a good start. It is not a neuropathologic study,

but it certainly suggests there may be a connection " between

methamphetamine abuse and parkinsonism.

Dr. Guilarte thinks it would be important to look at the incidence of

movement abnormalities in younger methamphetamine abusers.

" In this study, they started looking at people at age 50 or above, when

idiopathic Parkinson's typically presents. Typically, methamphetamine

abuse starts in the teen years or early 20s, and it would be interesting

to see whether you can express movement abnormalities before 50 years of

age. If so, then it might suggest that methamphetamine use is a risk

factor, " he explained.

The study was supported by grants from the Ontario Ministry of Health

and Long-Term Care to the Centre for Addiction and Mental Health. Dr.

Callaghan has received funding from the Canadian Institutes of Health

Research, Public Health Agency of Canada, and Ontario Tobacco Research

Unit. A complete list of author disclosures (none of which are drug

company related) appears in the original article. Dr. Guilarte has

disclosed no relevant financial relationships.

Mov Disord. Published online August 24, 2010.

http://www.medscape.com/viewarticle/728067?sssdmh=dm1.635913 & src=nldne & uac=66422\

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