Link Between Migraine and Parkinson’s Found
The study looked at a sizeable cohort of 41,019 subjects (aged 40 to 90 years), who had had at least two migraines during 2001. The researchers then studied 41,019 randomly selected subjects without migraine. Patients were matched to the migraine cohort based on age, sex, pre-existing comorbidities, and socioeconomic status.
The researchers, from the National Taiwan University Hospital, noted that none of the subjects in the study had been diagnosed with PD or secondary Parkinsonism in the year prior to the study. However, at the 32-month follow-up, 148 patients with migraine were diagnosed with PD, compared to just 101 patients without migraine (hazard ratio (HR) of 1.64; P=0.0004). The PD-free survival rate for the migraine group also was found to be significantly lower than that for the non-migraine group (P=0.0041).1
How Migraines Increase the Risk of Parkinson’s
A link between migraine to PD is not a novel idea. Movement disorders, like PD, appear to be overrepresented in people that experience migraines, suggesting a causal link between the two conditions.2
In 2014, Scher et al found that subjects in the AGES-Reykjavik study (born between 1907-1935) with midlife migraine, specifically migraine with aura (MA), were far more likely to report parkinsonian symptoms and be diagnosed with PD.3
Furthermore, migraineurs appear to have a high frequency of many other basal ganglia disorders, like essential tremor, Tourette's syndrome, Sydenham's chorea, and restless legs syndrome. However, researchers agree that more controlled research is needed to better understand these possible associations.2
According to the current study authors, one plausible mechanistic link could be dopaminergic dysfunction, something common to movement disorders like parkinsonism. Of note, dopaminergic dysfunction has been a proposed causal factor in migraine pathogenesis for some time,4 as excessive yawning, nausea, and vomiting are common prodromal and accompanying symptoms of migraine. This could be related to stimulation of DA receptors. Even pharmacologic studies using DA agonists have suggested a role for DA hypersensitivity in migraine patients.5
There is also a suggestion that both migraine and PD can arise as the result of dysfunctional iron metabolism. Iron, an essential nutrient for DA regulation,6 does appear to have increased accumulation in deep brain nuclei of migraineurs,7-9 which experts suggest possibly could be a marker of tissue damage from other processes, or an unrelated reversible epiphenomenon.6,7,10
Traumatic brain injury (TBI) could be another possible link between migraine and PD. Targeted DAergic therapies appear to have a counteractive effect on the cognitive damage caused by TBI,11 and posttraumatic headache is a common manifestation of TBI.12
Limitations to the Study
The data, supplied by the Taiwanese National Health Insurance claims database, excluded relevant lifestyle factors, like past occurrence of head injury, smoking, alcohol intake, and obesity, a limitation that may have influenced the findings, according to the study authors.
The median follow-up time of 32 months may seem comparatively short compared to other longitudinal investigations, like Scher et al’s analysis of the AGES-Reykjavik cohort that occurred after several decades.3 Having a follow-up of < 3 years may have prevented the researchers from better understanding the long-term effects of migraines on PD risk, the authors wrote.
And while the authors noted there could be some bias to consider, given both conditions are neurological, the study benefits from its large sample size and offers useful evidence supporting a positive association between migraine and PD for researchers to consider further.
Experts now suggest that future studies, perhaps using targeted brain imaging and neurologic examinations (4), someday could elucidate even more insights behind the cerebral vulnerability migraine possibly shares with PD, a development that could lead to a better understanding and treatment of the 2 conditions.
This research was conducted by a team of researchers of the National Taiwan University Hospital and the National Taiwan University College of Medicine. The study was published in Cephalagia, and the official abstract can be found here. This study was published online before print. No relevant conflicts of interest were reported on the official abstract.