Studies show that increased oxidative stress (from excess free radicals) may damage brain cells and is linked with Alzheimer's disease (AD). Many studies show increased oxidation of brain lipids (fats), proteins, carbohydrates (sugars) and DNA in AD. Although the causes of AD are not known, it is believed that oxidative stress is part of what damages brain cells in AD and probably other brain diseases. Animal and tissue culture studies of vitamin E and selenium suggest that they can protect brain cells from damage. This research study is being done to see how safe and effective vitamin E and selenium may be in preventing AD and other brain illnesses. These illnesses are more common in people over the age of 60 to 65. A potential benefit of participating in the PREADVISE study is that early detection of memory changes can lead to early diagnosis and treatment. Also, some participants may decrease their risk of getting AD if the supplements are effective. The findings of this study may also help in the research and understanding of AD.

Only participants who are taking part in the SELECT study (a study that looks at the use of vitamin E and selenium for preventing prostate cancer) may apply to participate in the PREADVISE study about how useful vitamin E and selenium might be for preventing memory changes with age (including Alzheimer's disease and other disease that can affect the brain). African American and Hispanic men who are age 60 or older may take part. Men of other ethnic groups aged 62 or older may take part. The SELECT doctors or staff will review the applicant's medical history and drugs to verify that they have no conditions that would exclude them from this study. About 10,000 men will take part in this study.

The PREADVISE study examinations will be done during the participant's annual SELECT visit at the clinic where the SELECT studies are being conducted. There will be one study visit for each year the participants are in SELECT (7 to 12 visits). Each visit for PREADVISE will consist of a brief screening of the participant's memory, and an update (if any) of the participant's family history of dementia and medications. If memory changes are suggested by the brief memory screen, the participant will be asked to take a longer memory screen to further evaluate the potential for memory changes. If the longer memory screen also suggests problems with the participant's memory, the participant will be asked to see his family doctor or a PREADVISE doctor for a more complete medical exam to find the possible causes of the memory change. Results of the doctor's medical exam, with the consent of the participant, will be sent to the PREADVISE doctors for their review to help with the diagnosis. Results of the memory checks will not be given to the participants. However, if the participant does have a medical workup for memory changes, this information will be given to the family doctor after the medical workup is completed. A portion of the blood sample that was taken when the participant entered SELECT might be analyzed and tested for a genetic risk factor associated with Alzheimer's disease, called Apolipoprotein E (ApoE). The results of this test will be used for research purposes only.