Nature Versus Nurture: What Causes PD?
Juliette Harris, Ph.D., M.S., C.G.C.

A marked change has occurred over the last decade in our understanding of the role of genetics in the causes of Parkinson's disease (PD). For many years, PD was considered to be a "sporadic" disease with no hereditary involvement. Then, beginning about a decade ago, intensive studies led to the discovery of a number of genes that play a role in the development of PD. There is now a consensus that PD, like heart disease, diabetes and Alzheimer's disease, is a "multifactorial" or "complex" disease that is caused by a mixture of environmental and genetic-susceptibility factors. This means that the cause of PD for most people is not found in genes or the environment alone, but in some interaction between them.

Environmental factors that can affect one's health include any influence exerted on the body after conception. These can include any events during fetal development and after birth -- such as physical trauma, exposure to chemicals and infections, and nutrition. Some studies, but not all, indicate that pesticide use, rural living and the drinking of well water -- all factors that increase exposure to pesticides -- contribute to the development of PD. Pesticides are thought to adversely affect the brain by inhibiting energy production resulting in brain cell death. Studies have also shown that smoking and caffeine use appear to protect against the development of PD. However, it is universally agreed that the health risks associated with smoking are worse than any incidental benefits that might be gained by this habit.

Genetic factors that can affect one's health are determined by our genetic make-up at conception and cause differences in the way our bodies work and respond to environmental factors. Scientists have learned about the role of genetic factors in PD by comparing groups of people with and without the disease,from twin studies and by studying a few rare families in which PD is "highly" genetic. In addition to showing that PD is a "complex" disease, studies have revealed that there may be more of a genetic basis to young-onset PD (that is, the 10 percent or so of people with Parkinson's for whom onset occurs at or before age 50) than to later-onset PD. Another view is that there may simply be different genes, or combinations of genes associated with early and late-onset PD.

If you'd like to read the entire story about new points of view on genetic and other causes of Parkinson's, please visit our website.

Desculpe o inglês; não estou em casa e não tenho ferramentas para editar. Isto é parte do último boletim da Parkinson´s Disease Foundation.