March 5, 2026

@michaelokun

Why is Parkinson disease growing worldwide? The 'bathtub analogy' explains the surge. A bathtub analogy means imagining disease cases like water filling a tub where inflow, outflow and drainage determine how high the water rises. Dommershuijsen and colleagues describe in a new paper in Nature Reviews Neurology how simple epidemiological dynamics help explain the worldwide growth of Parkinson disease. They apply the bathtub metaphor. Key Points: - The bathtub water level represents the total number of folks living w/ Parkinson's disease, and this level has risen dramatically worldwide over the past decades. - Inflow into the bathtub represents new cases and may rise due to population aging, environmental exposures and better detection of Parkinson's. - Outflow represents deaths or cures, and longer survival w/ Parkinson's means less water draining from the bathtub and a steadily rising level. My take: The bathtub analogy is a powerful way to understand the Parkinson pandemic. Even if the rate of new diagnoses stays stable, the total number of folks living w/ Parkinson disease can keep rising because more folks survive longer and populations are aging. This framing also reminds us that prevention, environmental protection and disease modifying therapies will be essential if we want to slow the rising water level. Here are 5 points that resonated w/ me: 1- Parkinson disease is the fastest growing neurodegenerative disorder worldwide and the number of affected folks continues to climb. 2- Population aging expands the reservoir of individuals at risk and adds more water flowing into the bathtub. 3- Environmental exposures across a lifetime may contribute to rising disease risk in many regions of the world. 4- Better recognition and earlier diagnosis mean fewer cases are missed, which also raises the apparent number of folks living w/ Parkinson's. 5- Slowing the Parkinson's pandemic will require prevention strategies, disease modifying therapies and ultimately cures. These strategies will actively pump water out of the bathtub. https://www.nature.com/articles/s41582-026-01193-z #parkinson #michaelokun #fixelinstitute