Environmental factors may impact Parkinson’s disease risk: Dutch study
More cases seen in residents of the Netherlands' northern provinces
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- Parkinson's disease incidence in the Netherlands is higher in men, older adults, and northern provinces, a study found.
- Geographic patterns indicate environmental influences, but specific causes like pollution or farming are not yet clear.
- New studies are underway to investigate specific environmental exposures, such as pesticides, and individual risk factors.
In the Netherlands, new cases of Parkinson’s disease occur more often in men, older adults, people with higher socioeconomic status, and residents of the northern provinces, suggesting that long-term environmental factors may contribute to the disease, according to a study from Utrecht University.
According to a university press release, “a higher number of diagnoses in a neighbourhood does not mean that everyone living there has a higher risk. Individual risks vary widely.”
The study, “Incidence and spatial variation of Parkinson’s disease in the Netherlands (2017–2022): a population-based study,” was published in The Lancet Regional Health – Europe.
Parkinson’s more often diagnosed in men than in women
Utrecht University and Radboud University Medical Center conducted the nationwide study. The researchers examined new Parkinson’s diagnoses made between 2017 and 2022, analyzing both how many people were diagnosed each year and where they lived at the time.
The study confirmed that Parkinson’s is more often diagnosed in men than in women, and that the risk rises strongly with age. It increases steadily throughout adulthood and reaches its highest level between the ages of 75 and 85. People with a higher socioeconomic status, such as higher levels of education or income, were also found to have a higher risk.
In addition, the researchers mapped the locations of new cases across the Netherlands. A heatmap — a color-coded map showing areas with higher or lower numbers of cases — revealed clear geographic patterns, with higher numbers in the northern provinces and lower numbers in the south. This uneven distribution is unlikely to be explained by chance alone and suggests that environmental factors may play a role.
This study was the first to measure Parkinson’s disease incidence nationwide. Incidence means the number of new cases in a given time period, not the total number of people living with the disease. To do this accurately, the researchers combined several sources of information.
They linked data from death certificates, hospital records, health insurance claims, and prescriptions for Parkinson’s medication. By combining these records, they developed a new method to identify people who were newly diagnosed. This information was then connected to data on age, sex, education, and neighborhood characteristics.
Number of new Parkinson’s cases each year has remained stable
The study found that the number of new Parkinson’s cases each year has stayed stable. On average, about 3,724 people were newly diagnosed each year during the study period, after adjusting for population size.
Even though the number of new cases is stable, the total number of people living with Parkinson’s in the Netherlands is increasing. This is because people are living longer with the disease. Better care, including the nationwide ParkinsonNet, a network of specialized healthcare providers for people with Parkinson’s, has improved survival and quality of life.
Clear regional differences were observed. People living in northern provinces had a higher risk than those in the south. These differences persisted even after accounting for age and sex, suggesting that where someone lives may matter.
The geographic pattern points toward environmental factors such as chemicals, pollution, diet, and workplace exposures. However, the pattern does not match obvious risks such as poor air quality or intensive farming. For example, air quality in the north is generally good.
This does not rule out environmental causes. Each exposure may have only a small effect, but because nearly everyone is exposed over long periods, the combined impact could be important. Parkinson’s likely develops after many years, often decades, of exposure.
A limitation of the study is that it only used people’s addresses at the time of diagnosis. Earlier living environments, jobs, and diets were not included. These details are often crucial because long-term personal exposure matters more than regional averages.
To address this, new studies are underway. One is the OBO2 program, which examines the health effects of pesticide exposure. Another is the PD-PEST study, the largest case-control study of Parkinson’s in the Netherlands, which also examines the role of pesticides and compares people with and without the disease to better understand individual environmental risks.
