A narrative review published in Experimental Neurology examined the neurological sequelae of methamphetamine use. According to this review, methamphetamine use in early adulthood is associated with increased risk of early-onset stroke, Parkinson disease (PD), and parkinsonism.
The present review sought to elucidate the neurological harms of methamphetamine, which are well-documented but poorly understood. Clinical evidence suggests that methamphetamine exposure damages the structure of dopaminergic neurons, which in turn impacts brain function.
Authors synthesized the results from prior studies and data from their own research group at the University of New South Wales in Australia. The epidemiology and clinical features of methamphetamine-associated stroke and PD were described.
Early-onset stroke, described as stroke in adults 45 years and younger, has a prevalence of 7 to 15 events per 100,000 people-years in the general population. In patients who use methamphetamine, however, the risk is substantially increased.
In a case series conducted from 2009 to 2015, 38 cases of death due to stroke were observed among 1649 cases of methamphetamine-related deaths. Two-thirds of these deaths occurred in patients 45 years and younger. All but one of these strokes were hemorrhagic, and intravenous methamphetamine use was the most common route of administration prior to stroke.
The clinical presentation for methamphetamine-related stroke is similar to that of nontraumatic stroke of any cause. The most common distinguishing factor of the patient is age; methamphetamine-related strokes occur in much younger individuals who tend to have fewer clinical risk factors for stroke.
The mechanisms implicated in stroke include methamphetamine-induced hypertension, tachycardia, thromboembolism, cerebral vasculitis, and vasospasms. Chronic methamphetamine use also damages blood vessel walls, which in turn increases their risk for rupture.
Overall, the fatality rate for methamphetamine-induced stroke appears to be much higher than the rate for other strokes of any cause. Methamphetamine users may also be at greater risk for permanent disability following stroke, with just 25% of individuals estimated to achieve complete recovery. Methamphetamine is thus a substantial cause of neurologically related death and disability, particularly in younger individuals.
The evidence linking methamphetamine to early-onset PD or parkinsonism is less complete. The prevalence of PD in the general population is estimated at 2% to 3% in individuals 65 years and older; development prior to age 50 is rare.
In population-based studies, the median age of PD development among methamphetamine users appears to occur several years earlier compared with the general population. In a 2015 study, the median age of PD onset was estimated at 45 years in a cohort of patients with past or current methamphetamine use. Two studies conducted in the US found an increased risk for PD or parkinsonism in the years following methamphetamine-related hospitalization.
The link between methamphetamine use and PD risk is hypothesized to result from methamphetamine-related structural damage to dopaminergic neurons. While few neurological imaging studies have been conducted in methamphetamine users, preliminary studies have found reduced dopamine levels and dopamine transporter availability in the brain following chronic methamphetamine use.
Few studies have examined the efficacy of pharmacological and nonpharmacological treatments for PD in patients with chronic methamphetamine use. Although methamphetamine abstinence has been found to improve dopamine availability in the brain somewhat, it is unknown whether sobriety reverses the risk for PD.
Further research is needed to better elucidate the neurological harms associated with chronic methamphetamine use, particularly the risk for PD and parkinsonism.
“Evidence from a variety of sources supports a link between methamphetamine use and increased risk for the earlier development of PD and parkinsonism, at least in a subset of individuals,” the study authors wrote.
Lappin JM, Darke S. Methamphetamine and heightened risk for early-onset stroke and Parkinson’s disease: a review. Exp Neurol. Published online June 21, 2021. doi:10.1016/j.expneurol.2021.113793