It is highly likely that the Parkinson’s results from a highly complex and interrelated combination of genetic and non-genetic factors.
These so called risk factors influence a person's risk to developing Parkinson’s disease. Currently, each of these risk factors is the subject of a great deal of research around the world.

The main risk factors for Parkinson’s Disease include:

 Age
 Sex
 Exposure To Pesticides And Herbicides
 Reduced Estrogen Levels
 Reduced Folate Levels
 Caffeine
 Non-Smoking

Each of these risk factors is discussed further below.

Age

Age is one of the main risk factors for Parkinson's Disease. Even though the disease can affect adults in their 20s, in the vast majority of cases it affects people over 50 years of age. The risk of developing Parkinson's Disease increase with age. Some researchers believe that neural damage from genetic or environmental factors may become worse over time, leading to the onset of the visible symptoms of Parkinson's Disease.

Heredity / Family History

Current research indicates that people with a family history of Parkinson’s are more likely to develop Parkinson’s themselves. However, it is rare for multiple people in one family group to suffer from Parkinson’s.
(Also see section 'Genetic Factors'.)

Sex

Research and history indicate that men are more likely to develop Parkinson's than women. This could be due to hormonal differences and life style differences, among other factors.

Exposure to Pesticides and Herbicides

Direct contact with herbicides and pesticides puts you at increased risk of Parkinson's. You also have a higher risk if you are involved in farming, live in a rural area, or drink well water.
(Also see section 'Environmental Factors'.)

Reduced Estrogen Levels

Estrogen, also known as oestrogen, is a group of steroid compounds that function as the primary female sex hormone. Estrogens are present in both men and women, but they are usually present at significantly higher levels in women of reproductive age. Estrogens promote the development of female secondary sexual characteristics, such as breasts, and are also involved in the thickening of the endometrium and other aspects of regulating the menstrual cycle.

Research indicates that reduced estrogen levels may cause an increased risk of Parkinson's Disease.

Menopausal women who receive little or no hormone therapy (HT) seem to be more likely to develop Parkinson's Disease. In addition, menopausal women who have had hysterectomies may also be at higher risk of developing Parkinson's.

Menopausal women using HT appear to have less chance of developing Parkinson's. However, not all of the effects of HT are positive. For example, taking HT as a combination therapy - estrogen plus progestin - can increase your risk of a range of serious side-effects.

Reduced Folate Levels

Folate is a B vitamin that is necessary for the production and maintenance of new cells. Folate occurs naturally in food. Folic acid is the synthetic form of this vitamin that is found in supplements and fortified foods. Folate is especially important during periods of rapid cell division and growth such as infancy and pregnancy, and it is also used to make normal red blood cells and prevent anemia.

Research indicates that low levels of folate may increase susceptibility to Parkinson's Disease. For example, researchers have found that mice with low folate levels developed severe Parkinson's symptoms, while those with normal levels remained healthy.
Low levels of folate have also been linked to the onset of a range of other serious diseases, such as cancer and heart disease.

Caffeine

Caffeine consumption, in moderation, has also been associated with a slightly reduced incidence of Parkinson's, in some studies.

Non-Smoking

A factor that has been consistently associated with a slightly reduced risk of Parkinson's, in numerous studies, is cigarette smoking. That is, smoking actually reduces your risk of developing Parkinson's.
It is not known whether smoking confers a genuine protective effect, or whether individuals who are prone to develop Parkinson's for other reasons are also prone to avoid smoking.

Nevertheless, the large negative impact on general health from smoking far outweighs any slight reduction in the risk of developing Parkinson's.

As such, smoking is not recommended as a strategy for avoiding Parkinson's Disease.