A new study hints at why forgetfulness plagues older men. Loss of testosterone, which happens normally as men age, seems to be at the root of some memory loss.

The research was presented at the Society for Neuroscience annual meeting in San Diego this week.

Previous studies have shown memory loss to be common in men with prostate cancer (search) who have had treatment with testosterone deprivation therapy (search). The therapy involves reducing the body's production of testosterone and is a common treatment for prostate cancer. However, it wipes out most of the male hormones in the body.

Receptors for testosterone are located in the brain's memory centers.

Testing Memory Loss in Cancer Patients With Low Testosterone

In this new study, researchers tested 14 men who had testosterone deprivation therapy and compared the findings with 16 men with normal testosterone levels.

Each volunteer was presented a list of words and asked to identify whether the words were in capital or lowercase letters — which requires "shallow processing" in the brain. The men were also asked whether the words represented objects that occurred in nature or were artificially made, which requires deeper processing.

But when handed another list — one with new words plus previous words — men with testosterone deficiency could not identify words they'd seen before. Memory loss was evident.

Testosterone-deprived men immediately grasped the new information but could not process and store it. They forgot it faster than the men with normal testosterone levels, reports lead researcher Joseph R. Bussiere, a graduate student in behavioral neuroscience at the University of Michigan in Ann Arbor.

Researcher Jeri Janowsky, PhD, professor of behavioral neuroscience and neurology at the Oregon Health & Science University, says testosterone-deprived men can "immediately get the information, but then the [brain] can't consolidate it and send it off for storage. When you look at their memory, they're perfectly normal when they're immediately asked to recall something, but they can't hold or save the information as well in order to recall it over a retention interval, over a period of time.

"They're faster at forgetting" Janowsky says in a news release.

This same memory loss pattern has been found in people with early Alzheimer's disease or strokes, researchers say.

By Jeanie Lerche Davis, reviewed by Brunilda Nazario, MD

SOURCES: News release, University of Michigan, Ann Arbor. Neuroscience 2004. San Diego, Oct. 23-27, 2004.