The two largest studies of Alzheimer’s disease have led to the discovery of no fewer than five genes that provide intriguing new clues to why the disease strikes and how it progresses.

Researchers say the studies, which analyzed the genes of more than 50,000 people in the United States and Europe, leave little doubt that the five genes make the disease more likely in the elderly and have something important to reveal about the disease’s process. They may also lead to ways to delay its onset or slow its progress.

“The level of evidence is very, very strong,” said Dr. Michael Boehnke, a professor of biostatistics at the University of Michigan and an outside adviser on the research. The two studies are being published Monday in the journal Nature Genetics.

For years, there have been unproven but persistent hints that cholesterol and inflammation are part of the disease process. People with high cholesterol are more likely to get the disease. Strokes and head injuries, which make Alzheimer’s more likely, also cause brain inflammation. Now, some of the newly discovered genes appear to bolster this line of thought, because some are involved with cholesterol and others are linked to inflammation or the transport of molecules inside cells.