A new synthesis of medical research reveals good news for those who thought that neurodegenerative diseases like Alzheimer's and Parkinson's are genetically determined and can not be avoided. In fact, the research shows that genetics plays a minor role -- if any -- in the overwhelming majority of cases. Far more important are environmental factors, including diet, exercise, exposure to environmental chemicals, air pollution, and socio-economic stress. By modifying these risks, the odds for delaying or preventing Alzheimer's and Parkinson's can be greatly improved.
This research is the first to draw together hundreds of studies across diverse fields -- including medicine, public health, nutrition, toxicology, evolutionary biology, environmental health, and ecology -- to provide compelling evidence that environmental factors are key drivers of Alzheimer's and Parkinson's diseases. Just as lead and other harmful exposures early in life can injure a child's developing brain, these exposures throughout the lifespan can injure the aging brain. When damage persists and accumulates, neurodegenerative disease may result.
In addition, connections between dementia, (the most common form of neurodegenerative disease), and chronic illnesses like diabetes, obesity, and cardiovascular disease have recently become apparent. These latter diseases are referred to collectively as the "Western Disease Cluster," because they are extremely common in Western cultures, and linked to the spread of Western lifestyles. These illnesses turn out to be important risk factors for dementia, with each of them roughly doubling the odds.
The Western Disease Cluster poses a growing public health concern throughout the developed world. In the United States, diabetes or prediabetes, already affects one out of every three U.S. adults, while two of every three are obese or overweight. Each of these conditions has roughly doubled in the past three decades. In addition, the U.S. population over the age of 65 -- the group most vulnerable to the impacts of the Western Disease Cluster -- is expected to nearly double by 2030, to over 71 million. If the upward disease trends continue, they will combine with the demographic shift to produce a staggering U.S. burden of chronic illness within a matter of decades.
Fortunately, there is much that we can do to avoid those health problems -- as a society, as individuals, and as family members. But it will require adopting a far broader "ecological" vision of what is required to achieve healthy aging.
To start, policy-makers and government officials have opportunities and responsibilities to safeguard health and the environment that health depends on. They can:
o Promote healthier food policies. Shifting towards more local, sustainable food systems can improve nutrition, food access and security, and reduce environmental degradation and greenhouse gas production associated with industrial agriculture and factory farming. Farm-to-school and community-supported agriculture programs can make healthier food readily available. Mandatory calorie counts on menus and transfat bans in restaurants are proven strategies for healthier eating.
o Reform chemical regulations. Require pre-market safety testing and safer substitutes for hazardous chemicals in consumer products, thereby reducing risks in homes, schools, and workplaces.
o Improve health care. Increase the focus on primary disease prevention and create a system for universally accessible, comprehensive and equitable health care.
o Transition to renewable, clean energy. Prioritize conservation and efficiency, and expedite the transition to clean renewable energy. This would reduce harmful exposures, greenhouse gas emissions and dependence on fossil fuels. Linking energy-efficient public transportation with bikeways and sidewalk networks would save energy while also encouraging physical activity.
For individuals and families, key priorities include:
o Eat healthy. Watch the nutritional and caloric value of what you eat; eat lots of fruits, green and orange vegetables, legumes, whole grains, and foods high in omega-3s (like fish, canola oil, and walnuts); avoid saturated, hydrogenated and transfats, as well as sugars, and limit consumption of refined carbohydrates (especially cookies, cakes, corn chips, crackers and refined cereals). As a general rule of thumb, eat mostly fresh plant-based foods and avoid fast, processed, and packaged foods. And, don't eat too much.
o Incorporate physical activity into daily life wherever possible. Aim for at least an hour of brisk walking or equivalent activity over the course of a day. If unable, do what you can.
o Avoid toxicants. Reduce exposure to hazardous chemicals at home and in schools and the workplace -- including substances like pesticides; metals such as lead and mercury; toxic solvents in glues, paints, varnish and degreasing agents; and endocrine disruptors like bisphenol A, which leaches into food and beverages from the lining of tin cans and polycarbonate plastic bottles.
o Be socially engaged. Stay active with family and friends; avoid social isolation, which is a risk factor for dementia.
The evidence is now before us. Modifiable environmental factors have a profound influence not just on cardiovascular disease, diabetes, and obesity, but on neurodegenerative disease as well. If we fail to act on this evidence, the implications will be enormous for us as individuals and for our rapidly aging nation.
The authors, both physicians, are co-authors of the recently published Environmental Threats to Healthy Aging (downloadable free at www.agehealthy.org). Schettler is Science Director of the Science and Environmental Health Network. Stein is a co-founder of the Massachusetts Coalition for Healthy Communities and a board member of Greater Boston Physicians for Social Responsibility.