Mayo study shows Parkinson’s disease increase over 30 years

The incidence of Parkinson’s disease and parkinsonism increased significantly in 30 years, from 1976 to 2005, according to Mayo Clinic research reported in JAMA Neurology. The increase was noted in particular for men age 70 and older. According to the Mayo researchers, this was the first study to suggest such an increasing trend.

The study showed that men of all ages had a 17 percent higher risk of developing parkinsonism and a 24 percent higher risk of developing Parkinson’s disease for every 10 calendar years. Men 70 and older had an even greater increase – a 24 percent higher risk of developing parkinsonism and a 35 percent higher risk of developing Parkinson’s disease for every 10 calendar years.

Researchers used the Rochester Epidemiology Project to look at the complete medical records of anyone in Olmsted County, Minnesota, who received at least one of the diagnoses related to parkinsonism. The records were reviewed by a movement disorders specialist to confirm the diagnosis and classify different types of parkinsonism.

“We have reasons to believe this is a real trend,” says Rodolfo Savica, M.D., Ph.D. (CTSC ’09, HSR ’09, MD ’12, N-DBS ’13, N ’13), Department of Neurology at Mayo Clinic in Rochester and lead author of the study. “The trend is probably not caused merely by changes in people’s awareness or changes in medical practice over time. We have evidence to suggest there has been a genuine increase in the risk of Parkinson’s disease.”

The researchers point to environmental and lifestyle changes as potential causes for the increase. “There has been a dramatic change in exposure to some risk factors in the United States,” says Dr. Savica. “We know that environmental agents such as pesticides and smoking and other agents have changed in the last 70 years or so. Changes in exposure to risk factors may have caused Parkinson’s disease to rise.”

The study, based on almost 1,000 patients affected by parkinsonism, is the first to consider long-term trends in risk over 30 years. It also provides evidence contrary to two previous U.S. studies and one Canadian study that showed no trend, and is particularly contrary to three United Kingdom studies that suggested a possible decline in the occurrence of Parkinson’s disease over time.

The Mayo Clinic study also revealed a possible higher incidence of both parkinsonism and Parkinson’s disease in men and women born from 1915 to 1924.

“This observation is important because the persons born in that decade may have been exposed to some environmental or other factors during their intrauterine life or early after birth that increased the risk,” says Dr. Savica. “We need to confirm this hypothesis.”

The study showed a similar trend in women – an increase in Parkinson’s disease in women 70 years of age and older. However, the trend in women did not reach statistical significance.

If the trend of increasing incidence rates is genuine and can be replicated in other populations, it has major implications for finding the cause of Parkinson’s disease and for public health, the researchers note. The trend should prompt studies to identify environmental or lifestyle changes – smoking, pesticide use, head trauma, coffee consumption and others – during the study subjects’ lifespan.