Ending Parkinson's Disease

A Prescription for Action


By Ray Dorsey, MD

By Todd Sherer, PhD

By Michael S. Okun, MD

By Bastiaan R. Bloem, MD, PhD

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In this “must-read” guide (Lonnie Ali), four leading doctors and advocates offer a bold action plan to prevent, care for, and treat Parkinson’s disease-one of the great health challenges of our time.

Brain diseases are now the world’s leading source of disability. The fastest growing of these is Parkinson’s: the number of impacted patients has doubled to more than six million over the last twenty-five years and is projected to double again by 2040. Harmful pesticides that increase the risk of Parkinson’s continue to proliferate, many people remain undiagnosed and untreated, research funding stagnates, and the most effective treatment is now a half century old.

In Ending Parkinson’s Disease, four top experts provide a plan to help prevent Parkinson’s, improve care and treatment, and end the silence associated with this devastating disease.


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Note to Readers

IN THIS BOOK, WE SHARE THE STORIES OF PEOPLE AFFECTED BY Parkinson’s disease. Most of these accounts are based on interviews we conducted. In some cases, individuals asked that their names be changed to protect their privacy; we note these instances in the text. Other stories are taken from published reports and are referenced as such.

The views expressed here are those of the authors and not necessarily those of their employers. The authors are devoting their net proceeds to efforts to help end Parkinson’s.


Below are definitions for key terms used in this book.

alpha-synuclein: A protein that is misfolded, or altered, in people who have Parkinson’s disease. The misfolded protein forms clumps in nerve cells and likely contributes to nerve cell death.

dopamine: A chemical that is released from nerve cells in areas of the brain that are affected by Parkinson’s.

levodopa: A drug that is converted into dopamine and is a highly effective medication for Parkinson’s disease.

Lewy bodies: The clumps of misfolded alpha-synuclein and other proteins that are found in the brains of individuals with Parkinson’s disease.

LRRK2: A specific gene that codes, or gives building instructions, for a protein in the brain and other parts of the body. Mutations in this gene are the most common genetic cause of Parkinson’s disease.

mitochondria: The energy-producing parts of cells, which are damaged in Parkinson’s and by some pesticides.

MPTP: An accidental chemical by-product of a street formulation of synthetic heroin. MPTP kills dopamine-producing nerve cells and has caused parkinsonism in some users of heroin.

neurotransmitter: A chemical that is released from nerve cell endings and enables communication between cells.

parkinsonism: A general term for any syndrome that causes tremors, slowed movements, stiffness, and imbalance. This condition has many causes, including Parkinson’s disease, certain medications, and other diseases.

pesticide: Any substance used to prevent, destroy, repel, or mitigate any pest, including herbicides (for weeds), insecticides (for insects), and fungicides (for fungi) among other chemicals.

substantia nigra: A Latin phrase that literally means “black substance.” It refers to a small region of the brain that contains pigmented dopamine-producing nerve cells, which are damaged in people who have Parkinson’s disease.


Below are common abbreviations used in this book.

EPA: US Environmental Protection Agency

FDA: US Food and Drug Administration

NIH: US National Institutes of Health

TCE: Trichloroethylene, a chemical that has been linked to Parkinson’s disease


Every civilization has its own kind of pestilence and can control it only by reforming itself.

—René Dubos, Mirage of Health, 19591

ON A BRILLIANT, BLUE-SKY DAY IN JUNE 2018, THE UNIVERSITY of Rochester hosted its annual Men’s Health Day at the Locust Hill Country Club in upstate New York. Over three hundred men, most in their fifties, sixties, and seventies, came to hear the latest on enlarged prostates, colon cancer, and heart disease. I came to speak about Parkinson’s disease.

Months earlier I had written a paper titled “The Parkinson Pandemic” with my friend and colleague—and now coauthor—Bas Bloem.2 In it, we explained that neurological disorders are the world’s leading cause of disability. And the fastest growing of these conditions is not Alzheimer’s but Parkinson’s disease. From 1990 to 2015, the number of people with Parkinson’s more than doubled from 2.6 million to 6.3 million.3 By 2040, the number will double again to at least 12.9 million, a stunning rise (Figure 1).4

This is what I know. This is what I study. But as I stood there in front of the packed room at Men’s Health Day, I was not prepared for what I was about to see. I opened my talk by asking how many people in the audience had a friend or family member with Parkinson’s. Before I could finish asking the question, over two hundred hands had flown up—almost the entire room. Everyone looked around. A silence settled on us as we took in the sight. It didn’t matter that I was an expert or that I had helped develop the statistics. Data always feel remote, but here it was in front of me, the evidence of the pandemic.

FIGURE 1. Estimated and projected number of people with Parkinson’s disease globally, 1990–2040.5

Parkinson’s disease is characterized by tremors, slowness in movement, stiffness, and difficulties with balance and walking. It can also cause a wide range of symptoms that are not visible—loss of smell, constipation, sleep disorders, and depression. Most people with Parkinson’s are diagnosed in their fifties or later. But it is not just a disease of the elderly. Up to 10% of those with the condition develop the disease in their forties or younger.

Parkinson’s stems from a loss of nerve cells in a particular region of the brain that produces dopamine, the brain chemical that helps control movements such as walking. The disease has multiple causes including environmental hazards—air pollution, some industrial solvents, and particular pesticides. In addition, certain genetic mutations, head trauma, and the lack of regular exercise all increase risk.6

The scale of the disease can feel overwhelming and the challenge daunting. But we can stop Parkinson’s in some cases, and we may already know how.

In the meantime, while there is no cure for Parkinson’s yet, many aspects of it are treatable. Just as exercise can reduce our risk of developing the disease, it can also help alleviate its symptoms.7 Medications aimed at replacing the dopamine that is lost in the brain are also beneficial. However, complications can develop with high doses or long-term use of some drugs. In certain cases, brain surgery can help treat these side effects.8

Although Parkinson’s is a progressive disorder—it becomes worse over time—most people can still live long and productive lives. Especially for the first five to ten years following diagnosis, individuals can function at high levels, working, traveling, and enjoying life.

Of course, the disease still takes a profound toll on individuals and their families. Up to 40% of people with Parkinson’s will eventually require nursing home care, and the caregiving burden is immense.9 Life expectancy is reduced modestly, and many die from falls or pneumonia.10

THE SEMINAL DESCRIPTION OF PARKINSON’S DISEASE CAME IN 1817, at the height of the Industrial Revolution in London.11 Dr. James Parkinson observed six individuals who walked with an unusual gait and had “shaking limbs.” Parkinson’s disease, as it became known, was almost certainly rare then.

Neither our increased awareness of the disease nor our lengthening lifespans can fully account for the upsurge in diagnoses that we now face. Our knowledge of another neurological disorder, multiple sclerosis, has increased too, and we have improved diagnostic tools for it. Rates for multiple sclerosis have indeed gone up, but that increase is nothing like the exponential rise of Parkinson’s (Figure 2). As for aging, more people are, of course, living longer. For example, from 1900 to 2014, the number of individuals over age sixty-five in the United Kingdom increased about sixfold. However, over that same period, the number of deaths due to Parkinson’s disease increased almost three times faster.

FIGURE 2. Number of deaths caused by Parkinson’s disease and multiple sclerosis in England, 1860–2014.12 Changes in coding in the 1980s likely contributed to the fluctuations in deaths recorded during this period.

How did we get here? While industrialization has raised incomes and life expectancies around the world, its products and by-products are also likely increasing the rates of Parkinson’s.13 Air pollution began to worsen in England in the eighteenth century, metal production and its harmful fumes increased in the 1800s, the use of industrial chemicals rose in the 1920s, and synthetic pesticides—many of which are nerve toxins—were introduced in the 1940s.14 All are linked to Parkinson’s—people with the most exposure have higher rates of the disease than the general population.

The evidence for this connection is overwhelming. Countries that have experienced the least industrialization have the lowest rates of the disease, while those that are undergoing the most rapid transformation, such as China, have the highest rates of increase.15 Specific metals, pesticides, and other chemicals have all been tied to Parkinson’s in numerous human studies.16 When animals are exposed to many of these substances in lab experiments, they develop the typical characteristics of the disease, including difficulty walking and tremors.17

Despite the vast evidence, we are doing little to manage these threats. The US Environmental Protection Agency (EPA) had at one time proposed banning one of the chemicals that is tied to Parkinson’s, a solvent called trichloroethylene. But after lobbying by the chemical industry, the EPA decided in 2017 to postpone the ban indefinitely.18 The uses of trichloroethylene have been so numerous and widespread—in washing away grease, cleaning silicon wafers, removing spots in dry cleaning, and even, until the 1970s, decaffeinating coffee—that almost all of us have been exposed to it at some point in our lives.19 Some of these uses continue today. Almost half of Superfund sites—land so polluted that the EPA or the responsible parties have to clean it up—which are found in nearly every state, are contaminated with trichloroethylene.20 Thousands of other sites are polluted across the country, including one, as I discovered in the process of writing this book, fifteen minutes from my home.21

As a result, up to 30% of the US drinking water supply has been contaminated with trichloroethylene.22 Because it readily evaporates from groundwater and soil, the solvent, like radon, can enter homes or offices through the air, undetected.23 Parkinson’s is not even the most concerning safety risk. According to the EPA, trichloroethylene also causes cancer.24

But trichloroethylene is only one dangerous chemical that we have failed to protect ourselves against. Paraquat is a pesticide that is so toxic that thirty-two countries, including China, have banned it.25 Exposure to the chemical increases the risk of Parkinson’s by 150%.26 Yet the EPA has done little. And as the agency charged with protecting our environment sits, paraquat’s use on US agricultural fields has doubled over the last decade.27

The nerve toxin chlorpyrifos is the most widely used insecticide in the country, drenching golf courses and dozens of crops, including almonds, cotton, grapes, oranges, and Washington State apples. It has been linked not only to Parkinson’s but also to problems with brain development in children. Again, the EPA has shelved a ban. When a federal court stepped in to take action against the chemical, the Trump administration appealed.28 And in July 2019 in response to a court ordering a final ruling, the EPA decided that it would allow continued use of chlorpyrifos.29

All of the evidence indicates that the full effect of the Parkinson’s pandemic is not inevitable but, to a large extent, preventable. However, we cannot remain silent.

We have been here before. We have faced down other difficult illnesses that have threatened us. Three of them—polio, HIV, and breast cancer—share similarities with Parkinson’s and offer valuable lessons for how we can take it on. Polio is a disabling neurological condition. HIV affected large numbers of individuals globally in a very short period. Breast cancer likely has both environmental and genetic causes.30 At some point, society ignored all three until the people who knew the diseases intimately—and understood their toll firsthand—stepped forward. Their activism changed the courses of these diseases and has improved and saved the lives of millions.

That is why we are writing this book. Yes, we are sounding the alarm that this pandemic is upon us. But we also know that if we respond now to the challenge it presents, we can save many people from suffering. Individually and collectively, we can take some very practical actions to stop the damage.

In Ending Parkinson’s Disease, we will discuss what new policies, protections, and resources can slow the disease. The Netherlands, for example, banned trichloroethylene, paraquat, and other pesticides linked to Parkinson’s years ago—and it worked. Rates of the disease decreased.31 This outcome shows how stemming the tide of Parkinson’s is within our reach.

We will also examine how we can offer better support and care to the millions affected by Parkinson’s today. We will see what new therapies are on the horizon and how close we are to introducing novel treatments that may slow or stop the progression of Parkinson’s. Some of these will arrive in time to help people who already have the disease. Others may even help to prevent Parkinson’s altogether.

At the end of the book, we outline what all of us can do to lower our risk, increase resources to address the condition, extend expert care to all those in need, and slow the advance of Parkinson’s.

Along the way, we will highlight the experiences of courageous individuals with the disease, tireless caregivers, and fearless advocates. We will hear their stories, learn from their experiences, and take inspiration from their actions.

The four of us—one neuroscientist and three neurologists who specialize in Parkinson’s—have devoted most of our professional lives to this disease. Twenty years ago, Dr. Todd Sherer conducted groundbreaking research linking pesticides to Parkinson’s disease. He now leads The Michael J. Fox Foundation for Parkinson’s Research, the largest private funder of Parkinson’s research in the world.32 Dr. Michael Okun, who first characterized Parkinson’s as a pandemic, has pioneered new surgical treatments for people with the disease and written multiple books and articles on the topic.33 Professor Bas Bloem is a leading authority on gait disturbances and falls in Parkinson’s and co-created the world’s largest care program for people with the disease.34 And with my colleagues, I have used technology to expand access to care and develop new methods for measuring the disease.35 All of us are working to advance better treatments for the condition.

While we are hopeful about making our patients’ lives better, our true passion is preventing people from ever having to face Parkinson’s. We are frustrated when we see women and men in our clinics who have suffered head trauma or been exposed to pesticides on a farm, solvents at work, contaminated groundwater in their neighborhoods, or polluted air in their homes. All of these risks for Parkinson’s can be mitigated. We humans have helped create this pestilence. And we can now work to end it.


A Formidable Disease



The Discovery of a New Disease and Its Causes

The unhappy sufferer has considered [the disease] as an evil, from the domination of which he had no prospect of escape.

—Dr. James Parkinson, “An Essay on the Shaking Palsy,” 18171

AT THE TURN OF THE NINETEENTH CENTURY, BRITAIN WAS booming and its Industrial Revolution was about to transform the world. Coal mining fueled James Watt’s steam engine. Iron smelting enabled the building of new bridges, while steamships and the telegraph linked disparate lands. The spinning jenny churned out wool and cotton, gas lights illuminated theaters, and author Jane Austen challenged social norms. Populations soared, and London, the epicenter of all of it, exploded with prosperity.2

The city was also becoming filthy. Humans and factories dumped their waste into the River Thames. Poor sanitation and overcrowding spread infectious diseases, including cholera, typhus, and tuberculosis. With the new industries came new chemicals and pollutants spewing from what the poet William Blake called “dark Satanic mills.”3

According to one environmental researcher, “It’s difficult to fully capture just how polluted London’s air was throughout the 19th century.”4 These industrial London fogs (Figure 1) were “often so dense that they… interrupted general economic activities, and even contributed to [the city’s] becoming a breeding ground for crime.”5 It was on these hazy streets that a seasoned physician observed something new.

FIGURE 1. Illustration of London fog, 1847.


A suffragist, activist, paleontologist, and advocate for the mentally ill, Dr. James Parkinson had many lives.6 Because of his politically radical stances, he used pseudonyms and, at one point, narrowly avoided imprisonment for his alleged role in a plot to assassinate King George III.7 However, his most enduring contribution to humanity was not his politics but a single essay that was destined to become a medical classic.

In 1817, Parkinson was a local doctor in Hoxton Square, London, where, almost two hundred years earlier, William Shakespeare had crafted many of his plays. Parkinson’s literary contribution was titled “An Essay on the Shaking Palsy.” By this time, he already had a wealth of clinical experience, gathered over more than thirty-two years of patient care.8 In his essay, Parkinson described six men, three of whom he had simply noticed on the street, who all shared similar characteristics—tremors, a bent posture, an abnormal walk, and a tendency to fall.9

Although ancient Chinese, Egyptian, Greek, and Indian texts provide rare depictions of some of these same symptoms, Parkinson’s essay was the most substantive.10 As he indicated, tremors had long been known and had multiple causes. However, the multi-symptom affliction that Parkinson was now observing on his walks had yet to be classified.11 His essay was well received, but its importance would not be recognized for decades.12

Fifty years after James Parkinson’s essay (Figure 2), Dr. Jean-Martin Charcot, the famous French neurologist, called the disorder “la maladie de Parkinson,” or Parkinson’s disease.13 Charcot added slow movements and stiffness to the list of key features.14 He also noted that not everyone with Parkinson’s disease had a tremor.

By the end of the nineteenth century, the clinical features of Parkinson’s disease were well known. In his 1892 medical textbook, Sir William Osler, the father of modern medicine, wrote, “When well established, the disease is very characteristic, and the diagnosis can be made at a glance.”15 While the external features of Parkinson’s were obvious, the underlying biological alterations were not.


What Parkinson and Charcot could not have observed in their time were the changes occurring in the brains of their patients. Scientists had long overlooked, downplayed, and ignored the chemical dopamine. But Dr. Arvid Carlsson, a Swedish pharmacologist working in the 1950s, saw dopamine differently.16 In experiments, he established that dopamine allowed nerve cells to communicate with one another. In other words, it was a neurotransmitter.

Carlsson also showed that a brain region important for movement contained high levels of dopamine. To demonstrate the chemical’s importance, he gave rabbits a drug that lowered dopamine levels in the brain. The rabbits lost their ability to hop and simply lay down. When they were given levodopa, a drug that is converted by nerve cells into dopamine, the rabbits regained their bounce.17

FIGURE 2. Two hundred years of Parkinson’s disease, 1817–2017.

Carlsson presented his research to the scientific community in 1960. He expected his peers to be excited. Instead, his research was greeted with almost universal skepticism.18 Some doctors even thought that levodopa might be a poison.19

Although stung at first, Carlsson would later say, “I am pleased [when] people are saying they don’t believe in me. Then I feel I’m probably on the right track.”20 And he was. His efforts and perseverance are the basis for what is still the most effective treatment for Parkinson’s and resulted in a Nobel Prize in 2000.

Notwithstanding the skeptics, other researchers picked up where Carlsson left off.21 They began measuring dopamine in the brains of deceased individuals. They found that levels of dopamine in the brains of people who had had Parkinson’s were ten times lower than in those without the condition. The levels were especially low in the same area of the brain that Carlsson had identified as typically dopamine rich. There was a simple relationship: the lower the dopamine levels, the worse the symptoms.22

This area of the brain that is normally dopamine rich is called the substantia nigra, Latin for “black substance.” It gets its name from the color of a pigmented chemical found in the region’s dopamine-producing nerve cells. In people with Parkinson’s disease, these nerve cells die off (Figure 3).

As it turns out, Parkinson’s affects more than just dopamine-producing nerve cells in the substantia nigra. Other regions of the brain producing different neurotransmitters also suffer cell loss.23 This additional damage is responsible for many of the symptoms of Parkinson’s that are not related to movement or “motor” function, such as disturbed sleep, anxiety, pain, and thinking difficulties.24 Some of these symptoms can be even more disabling than the motor symptoms controlled by dopamine.25

Based on Carlsson’s breakthrough with rabbits, researchers later tried levodopa in humans. The results were spectacular.26 “Bed-ridden patients who were unable to sit up, patients who could not stand up when seated, and patients who when standing could not start walking performed all these activities with ease after [levodopa],” the doctors wrote. “They walked… and they could even run and jump.”27 Multiple clinical trials would later replicate these dramatic effects.28 Dr. George Cotzias, a Greek American scientist who led many studies of levodopa, called it a “true miracle drug… of our age.”29

FIGURE 3. The substantia nigra (Latin for “black substance”) in individuals without and with Parkinson’s disease. In Parkinson’s, the substantia nigra is one of the key regions in the brain where cells die.


A dopamine deficiency was now understood to cause many of the symptoms of Parkinson’s. But no one knew what killed the nerve cells that produced it. Dr. Parkinson had speculated that the disease was caused by compression of the lowest part of the brain.30 Sir William Osler, one of the founding professors of Johns Hopkins Hospital, theorized that “exposure to cold and wet and business worries and anxieties” were possible causes.31 Neither was right. The first real insights came from an unlikely source.

On July 16, 1982, at a hospital in San Jose, California, a neurology resident interrupted Dr. William Langston’s morning cup of coffee. “Dr. Langston, you have to come down here,” he said. “I’ve never seen anything like it, and no one is sure what this patient has.”32

George Carillo, a forty-two-year-old man with a history of substance abuse, had just been admitted to a locked psychiatric unit. According to Langston, “The patient’s condition was indeed extraordinary. He was clearly awake, but had virtually no spontaneous movement.… [He] looked like a textbook case of advanced [Parkinson’s disease] before the days of levodopa. But this case didn’t fit.… He was in his early forties, and his symptoms came on literally overnight. We had a first class ‘medical mystery’ on our hands.”33


  • "Over the next 25 years, the number of people with Parkinson's disease is expected to double to at least 12.9 million. With its forecasted exponential rise, most of us will either be affected personally within our own families or know someone with the disease. This book is a must-read for all of us who are or might be affected. It pulls no punches with regard to the seriousness of this emerging pandemic, and its common-sense environmental approaches and precautions, if implemented, will abate the spread of this insidious disease. I know this to be true. I lived it."—Lonnie Ali
  • "This book offers a clear pathway forward - while sounding out a resounding clarion alarm; prompting action - that we should all pay heed to!"—Davis Phinney, Founder, Davis Phinney Foundation for Parkinson's
  • "This book shines a light on the environmental factors that put us all at risk for the disease. As a person with Parkinson's and as a father, I hope we will take the urgent action outlined in this important book to stop the growing number of people who will receive a diagnosis."—Brian Grant, former NBA player and Founder of the Brian Grant Foundation
  • "This book shines an essential spotlight on the need to end Parkinson's, illuminating the key issues we are all facing. It is the role of everyone in the Parkinson's community, patients, researchers, clinicians and advocates, to share this book and ensure that the authors' voices are heard."—Helen Matthews, Deputy CEO, The Cure Parkinson's Trust
  • "Parkinson's disease is not one disease but rather a collection of many with different contributing factors, and it satisfies many of the criteria of a pandemic. While the authors of Ending Parkinson's Disease are hopeful about making patients' lives better, their real passion is clearly centered around preventing people from ever having to face the disease in the first place. The book is a real eye-opener for people with Parkinson's, caretakers, and healthcare professionals, and should be used by activists all over the world in their discussions with politicians, policy makers and budget holders."—Susanna Lindvall, vice president, European Parkinson's Disease Association, EPDA
  • "A provocative read. It will certainly encourage you to consider what more you can be doing in the fight against Parkinson's Disease."—Leslie Chambers, MSPH, President and CEO of American Parkinson Disease Association (APDA)

On Sale
Mar 17, 2020
Page Count
336 pages

Ray Dorsey, MD

About the Author

Ray Dorsey is the David M. Levy Professor of Neurology at the University of Rochester, where he directs the Center for Health + Technology. For the past decade, he has pioneered technology to care for individuals with and measure the features of Parkinson disease. His research has been published in the leading neurology, medical, and economic journals and been featured on NPR and in The Wall Street Journal, and The New York Times. Previously, Ray directed the Parkinson disease division at Johns Hopkins Medicine and consulted for McKinsey & Company.

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Todd Sherer, PhD

About the Author

Todd Sherer, PhD, is the Chief Executive Officer of The Michael J. Fox Foundation for Parkinson’s Research, the largest nonprofit funder of Parkinson’s research. Trained as a neuroscientist, he is responsible for the Foundation’s overall scientific and fundraising direction to speed treatment breakthroughs and a cure for Parkinson’s disease. After a postdoctoral fellowship at Emory University investigating the role of environmental factors in Parkinson’s, Todd joined the Foundation’s staff in 2004 and was named Chief Executive Officer in 2011.

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