Oct. 30 (HealthDay News) -- Illness and surgery don't contribute to long-term cognitive decline in seniors and don't accelerate progression of dementia, researchers say.

The findings of a new study, published in the November issue of Anesthesiology, challenge the widely held belief that elderly patients suffer major deterioration in mental function after surgery.

"The concerns surrounding postoperative cognitive decline (POCD) following surgery certainly will not evaporate following publication of this study," researcher Michael S. Avidan, of the Washington University School of Medicine, said in a news release from the American Society of Anesthesiologists. "The important message to take from these findings is that persistent cognitive deterioration following surgery might not be a major public health problem. The decision to proceed with surgery should presently be made based on a person's general health and the specific risks and benefits of the procedure."

For the study, Avidan and colleagues looked at 575 patients tested annually at Washington University's Alzheimer Disease Research Center. At the start of the study, 361 patients had very mild or mild dementia and 214 were dementia-free. The patients were divided into three groups -- those who'd undergone non-cardiac surgery, those with illness, and those with neither.

Long-term follow-up showed no difference in cognitive decline among the three groups. Patients with dementia did have a more marked cognitive decline than those without dementia. Among those without dementia at the start of the study, 23 percent developed detectable cognitive impairment during the study period, but the decline was not more common among those who had surgery or illness, the researchers found.

"With mounting basic science studies implicating POCD as a real phenomenon, coupled with long-term outcome studies associating POCD with increased mortality, it is now imperative to conduct properly designed studies with meaningful clinical endpoints to determine whether any specific surgery, anesthetic technique or patient characteristic might be independently associated with long-term POCD," Avidan said.

SOURCE: American Society of Anesthesiologists, news release, Oct. 26, 2009