Alzheimer's Disease - Where Are We Today?

By Michael Craig Miller, M.D.
Content provided by the Faculty of the Harvard Medical School

Alzheimer's disease is a frightening illness. It threatens to rob people of their memories of themselves and how to do normal daily activities.

We don't yet know how to prevent or cure Alzheimer's disease. We do know some of the risk factors — age, family history, and inheriting some unlucky genes. But it's still unclear what sets off the disease process.

Here's an update on recent research to help understand and treat this illness.

Scrubbing Away Amyloid

People with Alzheimer's develop sticky deposits in the brain called amyloid protein. Experts believe that these proteins disrupt communication along brain circuits.

Researchers have been trying to develop medicines that can either clear amyloid deposits from the brain or prevent them from forming in the first place. Their hope is that these drugs, if given early enough, might halt or even reverse the Alzheimer's disease process.

But so far, the results have been disappointing:

  • Pharmaceutical companies had to stop working on two promising compounds because clinical trials showed that they were no better than placebo pills at improving patients' memory or thinking.

  • Researchers thought a new vaccine would trigger the immune system to clear the brain of the amyloid deposits. But the vaccine caused brain inflammation in 6% of patients.

The vaccine research led to an interesting discovery, however. The vaccine did clear deposits from the brains of some of the patients. But those patients still developed severe dementia. This finding suggests that the amyloid deposits may not be the right target.

Other Possible Targets

Researchers are now looking for new approaches to treatment.

Nature Medicine published a study last year from Brigham and Women's Hospital and Harvard Medical School showing that toxic fragments released by amyloid deposits may kick the Alzheimer's disease process into gear.

Researchers also are focusing on the brain's blood supply. The same factors that damage blood vessels and increase the risk of stroke may also contribute to thinking problems in Alzheimer's. So they are looking at whether statins might also reduce the risk of dementia. Statins are drugs that lower cholesterol levels.

Two studies of statin use had conflicting results. They were published within months of each other in Neurology last year:

  • The Religious Orders Study has been following 929 Catholic nuns and priests who were 75 years old, on average, when they entered the study between 1994 and 2006. Each year researchers test the participants' thinking and memory skills. Taking statins has not protected against Alzheimer's. Taking statins also has not slowed the disease once it started.

  • The Sacramento Area Latino Study on Aging began in 1998. It followed 1,674 people who were 60 or older. After five years, people who took statins were about half as likely to develop dementia or thinking problems, compared with those who did not take statins. Some critics pointed out that the result seemed too good to be true. One reason was that 42% of people in the study took statins for less than 2 years.

No doubt we need a lot more study to find reliable new treatments.

We're Not There Yet

The research on other Alzheimer's treatments has also been disheartening.

B vitamin supplements – Folate and other B vitamins reduce the levels of homocysteine. This is an amino acid. At high levels, it may increase the risk of heart disease and stroke. In 2007, a review of 14 small studies concluded that vitamin B supplements did not protect thinking ability in healthy people, or in people who already had some thinking problems. A larger, 18-month study of 340 people was also done. It showed that vitamin B supplements did lower homocysteine levels. This didn't protect people against Alzheimer's, however.

Ginkgo biloba – This dietary supplement is often promoted as a memory booster. But it came up short in a study of 3,069 people 75 years or older. All of the poeple in the study were healthy or had only mild thinking problems when the study started. They were randomly assigned to take ginkgo biloba or a placebo pill. After six years of treatment, both groups were equally likely to have developed Alzheimer's. Ginkgo biloba also did not stop mild thinking problems from getting worse.

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More than 5.3 million people in the United States are living with Alzheimer's disease, with a new person developing the disease every 70 seconds. Americans ages 65 and older with Alzheimer's and dementia pay three times as much in health care costs.