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Small Intestinal Bacterial Overgrowth (SIBO) associated with MCI and AAMI

Why is this study being done ?
The purpose of this study is to see if bacterial overgrowth in the small intestine is related to memory problems in older people. This study is being done because we think small intestinal bacterial overgrowth (SIBO) may be a cause of MCI and AAMI. Normally, the small intestine is free of bacteria, but in the condition of SIBO, large quantities of bacteria are found in the small intestine. We think SIBO may produce an abnormally large quantity of hydrogen sulfide. Hydrogen sulfide in the brain has been shown to be involved in learning and memory. However, a large amount of hydrogen sulfide produced from the small intestine may reduce the amount of hydrogen sulfide in the brain, which may affect memory.

What will participation in this study entail?

Your participation in this study involves 1 clinic visit. You will have the following tests and procedures.

Before the clinic visit: You will be asked to eat a light dinner and not eat anything before coming to your clinic visit, starting at midnight the night before.

At the clinic visit: You will fill out questionnaires about your medical history and current symptoms, take a lactulose hydrogen breath test, which is a test for small intestinal bacterial growth, and a methionine loading test to measure the amount of a substance called homocysteine in your body. Your breath will be measured for hydrogen content. Several memory tests will be administered between breath tests. Blood samples will be drawn to measure homocysteine and products of hydrogen sulfide metabolism. The visit will end with a small meal which will be provided. The clinic visit should take about 5 hours.

Who is eligible to participate in this study?

You can be eligible for this study if you are between 50 and 70 years of age.

How can I enroll in this study?
This study is currently enrolling volunteers. If interested, please contact:
Maya Slowinska (
University of Southern California Keck School of Medicine
Phone: (323) 442-7600

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