Risk factor AD

The following are some of the risk factors that are thought to have some relationship on the development of AD. Many of these risk factors are still being studied.

Table 6.  Some Risk Factors Associated with Alzheimer disease1^, 2^, 3^, [i]

Risk factor
Age	§  High life expectancy. Normal aging process increases the risk of AD.
Positive family history	§  Studies indicate that AD may be inheritable. Relatives with AD (i.e. parent or sibling) are at a risk for developing AD. §  Recent research has identified the presenilin 1 gene on chromosome 14 and the presenilin 2 gene on chromosome 1. Both genes appear to be strong indicators for Alzheimer Disease at an early age of onset (before the age of 65). 3 §  Preliminary research has also found markers on chromosomes 9, 10 and 12 that might be linked to late-onset Alzheimer Disease (over the age of 65). Several research studies are underway collecting blood samples from people with Alzheimer Disease and their family members. These samples enable scientists to analyze DNA material within families with the intent of identifying genes that may be responsible for causing Alzheimer Disease.3

Risk factor
Down Syndrome	Almost all individuals with Down syndrome over the age of 40 have changes to brain cells characteristic of Alzheimer Disease. In these individuals, dementia usually develops in 50's or 60's of age.
Head injury	Some studies have shown that people who have had a head injury with loss of consciousness have an increased chance of developing Alzheimer disease. Research into the development of AD as a result of head injuries is ongoing.3  The increased risk is probably due to the upregulation of APP seen after brain trauma.
Education	Several studies have shown that people who have less than six years of formal education appear to have a higher risk of developing AD. Low education may reflect early experiences that were not beneficial to brain development. Higher education is thought to delay the onset of symptoms of Alzheimer Disease probably due to greater brain reserve or educational activities that may stimulate brain activity. Education as a protective factor requires more study to determine whether it is education that makes a difference or other factors related to it (e.g., income level).2,3
Aluminum	The correlation between AD and aluminum is still under debate in the scientific community. Some studies have indicated that exposure to aluminum in drinking water may increase the chances of individuals developing Alzheimer Disease.2
Estrogen	Research has been conducted on estrogen and its impact on various diseases, including AD. Current research indicates that combined estrogen therapy (estrogen plus progestin) in women over the age of 65 doubled their risk of developing Alzheimer Disease and Vascular Dementia, over a five-year period. Research continues to investigate the effects of estrogen-only therapy on cognition. Previous research has shown that women with Alzheimer Disease who were treated with estrogen showed no sign of improvement. 2,3
Social, productive and Physical activity	Recent data from the CSHA-2 (Canada Study for Health and Aging) show that regular physical activity was associated with reduced risk of AD. This information supports previous clinical trials showing exercise to benefit cognitive function. Identifying the protective effect of regular physical activity is an important finding since it may represent a relatively safe and available strategy to help prevent AD, as well as many other chronic conditions. The CSHA-2 recommends that further research still needs to be conducted in this area.3
Comorbid diseases	Hypertension, high cholesterol, diabetes mellitus and low estrogen may affect the development of AD. Co-morbid diseases that may affect the development of AD are being researched.2,8,11
Other risk factors being studied	Other factors being investigated by researchers in relation to Alzheimer Disease include: §  Existing diseases or conditions that a person may have (such as heart disease, high cholesterol or high homocysteine levels in the blood) §  Toxins in the environment (such as fertilizers or pesticides) §  Antioxidants (such as vitamin E) Lifestyle choices (such as wine and coffee consumption, and diet)

---

[i] Förstl H. Clinical Issues in current Drug Therapy for Dementia. Alzheimer Disease and Associated Disorders. 2000; 14. s 1: s 103-s108.