Microsoft Corp. has agreed to acquire a company that operates a search engine for health information, one of the most popular search topics online.

Microsoft expects that the acquisition of privately held Medstory Inc. will improve its health-search offerings and anchor a “broader consumer health strategy,” the company said in a statement released Monday at the Healthcare Information and Management Systems Society conference in New Orleans.

Microsoft rival Google Inc. has tuned its Web search engine to recognize health-related queries and give users various options to refine their results by clicking on links for topics like treatment, tests, symptoms and causes.

About 113 million adults in the U.S., equivalent to 80 percent of U.S. Internet users, have searched for health information online, according to a Pew Internet & American Life Project study published in October 2006. People often seek information about diseases, treatments, diets, nutrition, fitness, medicines, doctors, hospitals and insurance, that study found.

About 8 million U.S. adults searched online for health information on a typical day in August of last year, which is about the same level of popularity online as topics like paying bills, reading blogs and looking up phone numbers or addresses, Pew found. More than two-thirds of people (66 percent) begin their health-related research at a search engine, while 27 percent start at a health Web site.

Monday’s statement didn’t say when the deal is expected to close, nor whether the company plans to integrate Medstory’s technology with Windows Live Search, Microsoft’s search engine. Microsoft didn’t immediately return a call seeking comment.

Medstory, in Foster City, California, will become part of the recently created Health Solutions Group at Microsoft. Financial terms of the acquisition weren’t disclosed.