Illness and surgery don't contribute to long-term mental decline in the elderly and don't accelerate progression of dementia.

Persistent postoperative cognitive decline is thought to be a public health problem, but its severity may have been overestimated because of limitations in statistical methodology. Therefore, researchers studied 575 patients of early Alzheimer’s disease (361 patients had very mild or mild dementia and 214 were dementia-free) to assess whether long-term cognitive decline occurred after surgery or illness by using an innovative approach to overcome some limitations. The patients were divided into three groups - those who had 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.

The researchers concluded that long-term mental decline is not due to surgery or illness, nor were these events associated with rapid progression to dementia. The decision to proceed with surgery in elderly people, including those with early Alzheimer disease, can be made without worrying about mental deterioration.