New research reveals that people with a history of methamphetamine dependence face a startling elevated risk of developing Parkinson’s disease or related movement disorders later in life.
Key Facts:
- Individuals dependent on methamphetamine had almost 3 times the rate of Parkinson’s outcomes compared to matched controls from the general population.
- For women with methamphetamine dependence, the risk was even higher – 5 times greater than women of similar ages without substance use histories.
- In contrast, dependence on the stimulant cocaine did not increase future risk of Parkinson’s disease.
- The findings fit concerning patterns of methamphetamine-induced damage to dopamine neurons in the brain.
Source: Drug Alcohol Depend.
What is Parkinson’s Disease?
Parkinson’s disease is an incurable, progressive neurodegenerative disease producing debilitating movement problems.
- Gradual death of dopamine neurons
- Build up of abnormal protein clumps
- Cardinal motor symptoms:
- Tremors
- Muscle rigidity
- Slowed movements
- Impaired balance
- Non-motor symptoms:
- Cognitive deficits
- Sleep disturbances
- Psychiatric problems
While causes remain unclear, research highlights roles for genetic susceptibilities and environmental toxic exposures.
Could methamphetamine constitute such an environmental risk factor for Parkinson’s pathogenesis?
Methamphetamine Dependence & Parkinson’s Disease (PD) Linked in Utah Study
To rigorously test this concerning possibility, University of Utah scientists leveraged an invaluable resource – the Utah Population Database (UPDB).
The Utah Population Database
Contains medical records from 1996-2011 for over 3 million Utah residents
Links to statewide birth, death, genealogical and other records
Includes data from: Inpatient hospitalizations, Outpatient clinics, Over 80% of patient encounters statewide.
This allowed researchers to follow two groups forward over time:
Exposed Group: 4,935 Utah residents diagnosed with methamphetamine dependence
Control Group: 24,675 Utah residents with no drug or alcohol history
Individually matched 5:1 to each methamphetamine user based on: Sex & Birth year.
Tracking Parkinson’s Outcomes
Researchers monitored these groups for diagnoses of:
- Parkinson’s disease
- Related conditions like parkinsonism and essential tremor
Stark differences emerged – methamphetamine users faced far higher rates of developing these dopamine deficiency disorders.
Main Findings: Methamphetamine Dependence Increases Parkinson’s Risk
By 2011, 30 methamphetamine users received diagnoses related to Parkinson’s disease:
- Half had Parkinson’s disease specifically
After accounting for mortality, methamphetamine-dependent individuals had:
- 2.8 times the risk of Parkinson’s
- 3.1 times the risk of Parkinson’s plus related diagnoses
Strikingly, for women the elevation was even more pronounced:
- 18 female methamphetamine users developed Parkinson’s spectrum disorders
- 5 times the risk compared to matched Utah women
- Male users still faced an increased risk of 1.9 times matched controls
However, sex difference was not statistically significant due to insufficient sample size and overlapping confidence intervals.
Cocaine Use Showed No Increased Risk
In contrast, dependence on psychostimulant cocaine did not raise future Parkinson’s disease risk.
- Only 4 of 1,867 cocaine-dependent individuals developed related diagnoses
- Matched rates to population controls
- Compared directly, methamphetamine users had almost 4 times the rate of Parkinson’s outcomes versus cocaine users
Meth & Dopaminergic Neurotoxicity in Humans
The discovery that chronic methamphetamine abuse boosts risk for dopamine deficiency disorders lends credence to preclinical neurotoxicity models.
If verified, the findings mean that methamphetamine may predispose users to developing Parkinson’s disease through long-term brain changes.
Exactly how methamphetamine could trigger Parkinson’s neurodegeneration remains unclear but potential mechanisms include:
- Oxidative stress
- Mitochondrial dysfunction
- Inflammatory changes
- Accumulation of aberrant protein aggregates
Regardless of mechanism, the end results are sobering. Decades after abuse, the drug appears to enact a slow but disastrous dismantling of motor control circuitry.
For comparison, well-established risk factors like rural living or pesticide exposure confer more modest elevations of 20-80% in risk.
Limitations & Future Research Directions: Stimulants & Parkinson’s Risk
While compelling, the retrospective nature means causality cannot be definitively determined.
Several aspects require further verification:
- Accuracy of diagnosis codes
- Confounding factors
- Treatment-seeking biases
However, the results reinforce similar earlier findings and align with concerning animal evidence.
Planned Follow-up Studies
Leveraging their unique Utah Population Database resources, researchers plan additional investigations:
- Refine Parkinson’s case definitions using detailed medical records
- Examine impacts of multidrug use patterns
- Analyze roles of genetic and family risk
- Compare psychiatric comorbidities between methamphetamine users and controls
- Determine if sex differences hold with larger sample sizes
Improving quantification of tobacco smoking will be critical, given the near ubiquitous rates among methamphetamine users.
Ultimately, the sobering likelihood that this drug sabotages dopamine neurons and Movement over the long-term accentuates the urgent need for better grasp of neurological impacts.
Methamphetamine Use Reaching Epidemic Levels
Once confined largely to the western United States, abuse of methamphetamine has exploded nationally over the past decades.
- Methamphetamine is an extremely addictive psychostimulant drug that powerfully triggers reward and pleasure centers in the brain.
- It can be smoked, injected, snorted, or taken orally, with effects including bursts of energy, hyperactivity, euphoria, and suppression of appetite.
However, chronic methamphetamine also ravages the body and mind, eroding physical and mental health.
Regional Use Trends
- In 2006, methamphetamine use in the last year among Americans over 12 was almost 1% nationally.
- But in the West, rates were over twice the national level at 2.4%.
- By comparison, past-year use in the Midwest and South were just 0.5% and the Northeast 0.2%.
State-specific surveys highlight the scale of the crisis in western states:
- In Utah, almost 4% of high school students reported trying methamphetamine.
- Over 9% of emergency room visits in Utah relate to methamphetamine toxicity.
Demographic Patterns
Certain demographic groups have been especially hard-hit:
- Although initiation often occurs in the late teens and early 20s, usage has spread across age groups.
- Importantly, women are nearly twice as likely as men to need hospitalization for methamphetamine abuse.
In Utah, over a quarter of female hospital admissions for drug dependence were methamphetamine-related.
The human costs of methamphetamine addiction are already clearly catastrophic – but what about the long-term effects on the brain and risk for neurodegenerative disease?
Methamphetamine Neurotoxicity in Animals
While the societal impacts have been evident for decades, scientists are still uncovering the biological devastation.
Studies in animals expose extremely concerning effects of chronic methamphetamine:
- Rats given high doses of methamphetamine show clear damage and death of dopamine neurons.
- These neurons play essential roles in motor control, motivation, pleasure and reward.
- Their progressive loss causes the hallmark movement abnormalities of Parkinson’s disease.
This dopamine neurotoxicity raises the terrifying question – could methamphetamine abuse predispose people to developing Parkinson’s disease or related disorders later in life?
Neuroprotective Agents May Help Counteract Risk
If substantiated, the methamphetamine-Parkinson’s link may galvanize research into urgently-needed neuroprotective therapeutics.
Currently, all available Parkinson’s medications just temporarily help replace lost dopamine or smooth symptoms.
None slow or halt the relentless progression of patients towards disability and dementia.
However, the prospect that methamphetamine sets in motion this neurodegenerative cascade decades prior to onset highlights a possible window for early intervention.
Identifying those at highest risk and developing treatments to interrupt pathogenic cascades before they culminate in substantial neuron loss is paramount.
The pressing challenge now falls to scientists to unravel mechanisms by which this drug exerts such enduring dopaminergic damage in order to pave way for neuroprotective strategies.
In the meantime, this research reinforces immediate need for better prevention and treatment of methamphetamine abuse and dependence.
Beyond profound psychosocial impacts, we now have further evidence of the potential to trigger insidious neurodegeneration of movement circuitry that may manifest years later as Parkinson’s disease.
References
- Study: Methamphetamine/amphetamine abuse and risk of Parkinson’s disease in Utah: a population-based assessment
- Authors: Curtin et al. (2014)
