As well as finding that meth users have three times the risk for getting Parkinson's disease, the researchers also observed that female meth users may be nearly five times more likely than women who do not use drugs to develop Parkinson's.
A previous study that examined nearly 250,000 California hospital discharge records found that meth users had an increased risk for Parkinson's. The new study - published in the journal Drug and Alcohol Dependence - includes both inpatient and outpatient clinic records, and so draws data from a wider sample of the population.
The researchers examined more than 40,000 records in the Utah Population Database (UPDB), which contains genealogical, medical and government-provided information on Utah families. Additional patient data was also provided from the University of Utah Health Care and Intermountain Healthcare to provide "a statewide perspective" on the research.
All identifying patient data was removed from the records so that all participants remained anonymous.
Looking at the period of 1996-2011, the team sorted the records into three groups:
- People whose health records indicated they had used meth (nearly 5,000 people)
- People whose health records indicated they had used cocaine (more than 1,800 records)
- A control group selected at random whose records showed no use of illegal drugs (more than 34,000 people).
Meth users who had a medical history of taking other illegal drugs or abusing alcohol were excluded from the study, as these factors could also have influenced Parkinson's risk. Members of the control group were matched to the participants in the meth and cocaine groups according to age and sex.
Cocaine users were included in the study to provide a non-meth illicit drug comparison and were not found to be at increased risk for Parkinson's.
"We feel comfortable that it's just the meth causing the risk for Parkinson's, and not other drugs or a combination of meth and other drugs," says senior author Glen R. Hanson, PhD, professor and interim dean of the University of Utah School of Dentistry and professor of pharmacology and toxicology.
Female meth users 'five times more likely' to develop Parkinson's than non-users
Fast facts about Parkinson's
- It is estimated that 4-6 million people worldwide have Parkinson's
- Symptoms include tremor, shaking, slowed movement, rigid muscles, loss of automatic movements and speech changes
- Although there is no cure for Parkinson's, symptoms can be alleviated by medications and surgery.
As well as finding that meth users have three times the risk for getting Parkinson's disease as non-users, the researchers also observed that female meth users may be nearly five times more likely than women who do not use drugs to develop Parkinson's.
However, the researchers are not sure why women who used meth appeared to be more at risk than men who used meth.
"Typically, fewer females use meth than males do," Hanson says. "Even though women are less likely to use it, there appears to be a gender bias toward women in the association between meth use and Parkinson's."
"Normally, women develop Parkinson's less often than men," adds co-author Karen Curtin, PhD, research assistant professor of medicine at the university and associate director of the UPDB.
"However, women may not achieve the same improvement in symptoms from medications or surgery," she considers. "If meth addiction leads to sharply increased incidence of Parkinson's disease in women, we should all be concerned."
The trend toward meth use in Utah is considered to be particularly pronounced in women in their late 20s, who are thought to begin taking the drug due to pressure from their partners.
"Female users in Utah may also get involved with meth because it's seen as a relatively cheap and effective way to lose weight and have more energy," Curtin says.