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CHE Science Director Ted Schettler, MD: Exposing Environmental Threats to Healthy Aging
-- Science Director, Science & Environmental Health Network --
As told to Shelby Gonzalez, CHE Administrative Coordinator
Nine or ten years ago, I worked on several projects with colleagues -- some of whom are coauthors of the Environmental Threats to Healthy Aging report -- looking at the impact of environmental factors on children’s health and development. We became curious about how environmental factors might be influencing the health of older people.
There's been interest in how environmental factors affect kids as they approach puberty, reproductive health in young adults, and so on. It was a natural progression to wonder how those factors affect people farther out along the arc of life. When we started exploring the literature, we quickly came to understand that there wasn't going to be any single cause that we could generally point to, with some obvious exceptions. In general, if you look at an entire population, you’re going to find a whole range of environmental factors that influence health throughout the years.
These factors range from diet and exercise to toxic exposures to social environment to the built environment. We also found that while we were interested in environmental influences on people as they age, we discovered that we had to look way back, even in utero, to begin to see those influences play out. We end up talking about the arc of life rather than about the elder years. Its shape and trajectory can be affected at any point along its path.
One of the interesting surprises in this work was that in a lot of work on Alzheimer’s there's a focus on the pathological markers -- plaques and tangles -- in the brain, which you can actually see under a microscope. There's a very large body of literature, however, showing very little correlation between the extent of that pathology in the brain and cognitive behavior of the patient while he or she is alive, particularly in older people. The correlation is greater in people with early-onset Alzheimer's disease.
There are things that can be addressed in people as they age: a nutritious, Mediterranean-like diet, high in fruits and vegetables, nuts, legumes, fish, omega-3 fatty acids or monounsaturated fatty acids like olive oil and at the same time is very low in saturated fats. Those data are really quite striking. It's may be possible to prevent or at least delay the onset and progression of the disabling symptoms with interventions like that.
The data for Parkinson’s Disease are less clear. It seeems clear that there are some features of diet that can influence PD that are very similar to Alzheimer’s. Diets high in saturated fats and having lower levels of antioxidants from fruits, vegetables and legumes seem to increase the risk PD as well as Alzheimer's disease.
It's not just diet. For Alzheimer's disease, tt's also social networks, social support, and intellectual stimulation. And increasingly there's evidence showing a relationship between exposures to certain toxic chemicals and increased risk of not only PD but also Alzheimer’s disease. The links between PD and pesticides are striking. We conclude in the report that the evidence is now sufficient to call it a causal relationship.
Studies in rodents and primates show that both prenatal and infant exposures to lead increase the risk of the pathologies of Alzheimer’s through modification of gene expression. The link between lead and Alzheimer’s and lead and PD is pretty well established now. Early-onset Alzheimer’s tends to have a somewhat stronger genetic component than later-onset Alzheimer’s.
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Many academics are beginning to organize their research programs along the lines of systems biology, but systems biology is still in its infancy, whereas we've got a long history.... many decades of experience.... of taking complex systems apart and studying them piece by piece. We're still just learning how to put them back together and study how they behave. We’ve bumped up against the limit of the reductionist approach. It's not that there's anything wrong with that approach; it just needs to be coupled with a systems approach.
One thing that's challenging is that we.... the general public, and medical and public health communities... don’t have a lot of practice finding crosscutting solutions. If you lay out a whole series of things that are contributing to a set of problems, people often feel overwhelmed. The challenge is to help people get beyond that sense of hopelessness and see that there are interventions that can be made.
We know enough to act and we have some pretty good ideas about what some crosscutting solutions to this constellation of problems would be. We also need to figure out the right level at which to make the interventions.
For example, you can address the combination of diet and nutrition, air pollution and other toxics relevant to these diseases through the redesign of agricultural systems that produce more nutritious food, raised closer to the point of consumption, requiring less transport and fossil fuel consumption and using less pesticides. These systems can also help to rebuild local economies.
In this country we have a long history of telling people about the kinds of problems I just described and then telling them how to change their own lives. But some of these problems can’t be solved at the individual level. You can take it up to the federal level with a new farm bill and chemical policy reform. Work can also be done at the community, regional and state levels. We're hoping that this report will stimulate communities to search for unique, creative solutions to their own particular problems.
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I continue to be surprised by the reach of CHE. I run into people all the time who have been on CHE calls or who are following CHE's work. CHE is serving a really important purpose in bringing together the diverse community of people concerned with environmental health.
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