Genetics play but a small role
Though genetics do play a role in developing Alzheimer’s and Parkinson’s, lifestyle and exposure to certain chemicals are larger factors in neurodegenerative disease. The October 2008 report Environmental Threats to Healthy Aging, the most comprehensive review of environmental risks on brain health, indicates that degenerative brain diseases can start in the womb and continue into adulthood.
A collaboration between Greater Boston Physicians and the Science & Environmental Health Network, the report describes substantial emerging evidence that, collectively, environmental factors alter the biochemical pathways at the cellular and subcellular levels. These biochemical changes fuel Alzheimer’s and Parkinson’s as well as other chronic diseases such as diabetes, obesity, cardiovascular disease and metabolic syndrome.
“As we explored origins and patterns of chronic degenerative diseases, we discovered a web of conditions in the environment -- including nutritional, chemical, physical and social factors -- that have a direct influence on the risk of Alzheimer’s, Parkinson’s and related chronic diseases,” says report co-author Jill Stein, MD, Greater Boston Physicians for Social Responsibility. “It is clear from these findings that our activities in the areas of food and agriculture, energy, chemical use and social organization are key drivers in the abnormal loss of neurological function in older people throughout the modern world.”
Environmental threats to brain health
The scientific analysis in the report draws attention to several specific environmental risk factors in the development of dementia, Alzheimer’s disease and Parkinson’s disease. They include, among others:
Lead -- Recent evidence links environmental lead exposure in the community to increased risk of cognitive impairment. For example, a recent study of elderly men found that the
highest lead-exposed group had, on average, an additional 15 years of cognitive aging compared to the lowest lead-exposure group. Several animal studies also suggest that exposure to lead in
infancy and childhood may sharply increase the risk of Alzheimer’s disease decades later. Evidence also implicates lead in increasing the risk for Parkinson’s disease.
Air pollution -- Recent studies show that air pollution is harmful to the brain, in addition to the lungs, heart, nose and blood vessels. This evidence is drawn from studies of
brains of people living in highly polluted cities compared with those living in clean air cities. These studies found evidence starting at young ages of inflammation and cellular damage associated
with both early Alzheimer’s and Parkinson’s diseases.
Pesticides -- A large body of data links exposure to a variety of pesticides with increased risks for Parkinson’s disease. Evidence also links chronic low-dose exposure to a
number of pesticides -- primarily in work settings -- with subsequent cognitive decline, such as impaired memory and attention. A study in France found that a history of occupational exposure to
pesticides more than doubled the risk of developing Alzheimer’s disease. Exposure to some pesticides has also been linked to dramatically increased risks for diabetes, prediabetes and
metabolic syndrome.
Dietary risk factors -- Diet and nutrition are emerging as critical factors in brain health and health in general. Several studies have shown that higher saturated fat intake
increases the risk of dementia by two to three times. Animal studies also suggest that young rats fed a high saturated fat diet had impaired learning and memory as adults compared to rats fed a
diet high in polyunsaturated fat. A number of studies also have raised serious concerns that infant soy formula or formulas fortified with the highest levels of iron may increase the risk of
Parkinson’s disease.
Dietary protective factors -- Diet and nutrition also can decrease the risk of neurodegenerative diseases. For example, numerous studies in people show that a high intake
of omega-3 fatty acids is associated with significantly lower risk for Alzheimer’s. In Alzheimer’s-prone laboratory animals, a high omega-3 diet started late in life reduced markers of
Alzheimer’s disease in the brain by more than 70 percent. The Mediterranean diet, which includes fresh fruit and vegetables, legumes, whole grains, fish, nuts and olive oil, is linked to
substantially reduced risks of both Alzheimer’s disease and Parkinson’s disease, as well as dramatically lower rates of diabetes, vascular disease, recurrent heart attacks and metabolic
syndrome.
Physical inactivity -- Being sedentary increases the risk of brain diseases and other chronic illnesses, and it follows that being physically active is linked to substantial
reductions in the risk of dementia and Alzheimer’s. One study found that subjects who were physically active at least twice a week in midlife had more than a 50 percent reduction in the risk
of dementia and Alzheimer’s diseases later in life.
Stress -- Stress can chronically up-regulate inflammation and oxidation in the body, which can initiate and promote neurodegeneration. Additionally, inflammation and oxidative stress are also associated with diabetes, cardiovascular disease, metabolic syndrome, lipid disorders, obesity, asthma and cancer.
Quick tips for healthy aging and brain health
Following a healthy lifestyle and reducing your exposure to environmental toxins -- regardless of your age -- can reduce your risk of developing Alzheimer’s, Parkinson’s and other chronic diseases significantly. This is especially important because the population older than 65, which is highly vulnerable to chronic disease, is expected to nearly double in the U.S. by 2030 -- from about 38 million to more than 71 million. With that increase will come a dramatic escalation of chronic diseases. Authors of the report recommend the following tips for aging healthfully (click the links for more information on each recommendation):
1. Improve your diet. Eat healthful, nutritious food, and avoid common hazards in the typical modern diet.
(The anti-inflammatory diet: Foods that heal)
2. Exercise. Engage in regular physical activity.
(New exercise guidelines for health)
3. Train your brain. Do mentally and intellectually stimulating activities every day.
(Brain training: 60 Days to a better brain)
4. Minimize your exposure. Avoid harmful chemicals, toxins and pollutants.
5. Be social. Stay socially engaged with family, friends and community.
In addition to these quick tips, it’s essential to advocate for change in public health policies to promote cleaner living. “As we illustrate in our report, the risk of neurodegenerative disease can be significantly impacted by individual lifestyle choices, such as by eating nutritious food, staying active mentally and physically, and avoiding harmful pollutants,” says report co-author Ted Schettler, MD, MPH, and science director for Science & Environmental Health Network. “However, these individual changes are not enough. Alzheimer’s and Parkinson’s disease risks are also heavily influenced by features of the family, community and society as a whole. Public health and policy approaches are essential for disease prevention.”
To read the full report Environmental Threats to Healthy Aging, visit AgeHealthy.org.
