Individuals with rosacea were nearly twice as likely to develop Parkinson’s disease as those without rosacea, based on an analysis of results of a nationwide cohort study of 5.4 million people conducted in Denmark. The findings were published online March 21 in JAMA Neurology.
Data from previous studies suggest a link between rosacea and Parkinson’s disease (PD), as both may stem from elevated activity of matrix metalloproteinases, wrote Dr. Alexander Egeberg of the University of Copenhagen, and his associates.
To explore the possible link between rosacea and Parkinson’s disease, the researchers reviewed data on about 5.4 million adults in a Danish database of all citizens aged 18 and older, over a 15-year period from January 1, 1997, to December 31, 2011. A total of 22,387 individuals were diagnosed with Parkinson’s disease and 68,053 were diagnosed with rosacea (JAMA Neurol. 2016 Mar 21. doi: 10.1001/jamaneurol.2016.0022).
The incidence of Parkinson’s disease was 7.62 per 10,000 person-years among rosacea patients vs. 3.54 per 10,000 person-years in the general population, the researchers noted.
Overall, the Parkinson’s disease risk was significantly higher among rosacea patients, with an adjusted incidence rate ratio (IRR) of 1.71 for rosacea patients compared with the general population. The IRR was even higher in patients with ocular rosacea (adjusted IRR, 2.03).
However, treatment with tetracycline appeared to reduce the Parkinson’s risk in the rosacea patients: After controlling for multiple variables, having filled a prescription for tetracycline was associated with a 2% drop in the risk of PD (adjusted IRR, 0.98).
A sensitivity analysis showed no dose-dependent relationship with disease severity; the IRRs for Parkinson’s disease in patients with mild rosacea and moderate to severe rosacea were 1.82 and 1.84, respectively. However, moderate to severe rosacea was defined as cases where tetracyclines were used, and the neuroprotective effect of tetracyclines might impact the relationship between rosacea and Parkinson’s disease, the researchers noted.
“It is tempting to speculate that, in patients with coexistent rosacea, Parkinson’s disease may display other phenotypic characteristics, and it is possible that rosacea-associated features, such as facial flushing, may contribute to support a Parkinson’s disease diagnosis at an early phase of the disease,” the researchers noted.
Limitations of the study include its observational design, which does not allow the establishment of causation, the researchers noted, and additional research is needed to confirm the observations and clinical consequences.
Lead author Dr. Egeberg was employed by Pfizer at the time of the study; one of the coauthors was supported by an unrestricted research scholarship from the Novo Nordisk Foundation.