The quest for ways to prevent Alzheimer’s disease is part of a broad research program that is exploring a number of possibilities. For example, scientists are looking at caregiver stress and physical frailty as possible risk factors for Alzheimer’s disease and MCI. Other areas of interest include hormones and immunization.
Scientists are studying hormones—especially those taken by older women as menopausal hormone therapy—for their potential ability to prevent or delay Alzheimer’s disease and age-related cognitive decline. Several clinical trials are testing forms of estrogen as well as testosterone and other hormones in both healthy older adults and those with MCI.
Hormones such as estrogen and progesterone have important effects on the brain, many of which could relate to cognitive aging and Alzheimer’s disease. Over the years, research has led to conflicting reports as to whether menopausal hormone therapy can prevent cognitive decline in postmenopausal women.
Some animal and observational studies comparing women who did and did not take estrogen have shown that the hormone may benefit cognition. However, clinical trials of estrogen and progestin in older women have generally failed to show similar beneficial effects. In fact, one large study showed that prolonged treatment with these hormones actually increased the risk of dementia in women 65 and older.
Researchers now wonder if it may be better for women to start taking hormones closer to menopause. NIA-funded clinical trials are studying the timing of menopausal hormone therapy on cognition and other health factors.
Other hormones being studied in clinical trials for their effects on Alzheimer’s and cognitive decline include testosterone, which is being tested in older men with MCI and low levels of the hormone; growth hormone releasing hormone (GHRH), in healthy older adults and those with early MCI; and DHEA, in healthy postmenopausal women.
The idea of a vaccine to prevent Alzheimer’s disease is under scrutiny as well. Early vaccine studies in mice were so successful in reducing deposits of Alzheimer’s-related proteins in the brain and improving performance on memory tests that investigators conducted preliminary clinical trials in humans with Alzheimer’s disease. These studies had to be stopped, however, because life-threatening brain inflammation occurred in some participants.
Scientists continue to refine this approach, hoping to maintain the vaccine’s possible benefits while reducing side effects. Several pharmaceutical companies are testing potential vaccines for safety and effectiveness in clinical trials.
The NIA is also supporting a clinical trial testing whether intravenous immunoglobulin (IVIg), a blood product containing naturally occurring antibodies that is used to treat immune-system disorders, may improve cognition by clearing Alzheimer’s plaques from the brain.