Exposure to general anaesthesia could increase the risk of dementia in elderly by 35 percent

Postoperative cognitive dysfunction, or POCD, could be associated with dementia several years later. POCD is a common complication in elderly patients after major surgery. It has been proposed that there is an association between POCD and the development of dementia due to a common pathological mechanism through the amyloid β peptide. Several experimental studies suggest that some anaesthetics could promote inflammation of neural tissues leading to POCD and/or Alzheimer's disease (AD) precursors including β-amyloid plaques and neurofibrillary tangles. But it remains uncertain whether POCD can be a precursor of dementia.

In this new study, the researchers analysed the risk of dementia associated with anaesthesia within a prospective population-based cohort of elderly patients (aged 65 years and over). The team used data from the Three-City study, designed to assess the risk of dementia and cognitive decline due to vascular risk factors. Between 1999 and 2001, the 3C study included 9294 community-dwelling French people aged 65 years and over in three French cities (Bordeaux, Dijon and Montpellier).

Participants aged 65 years and over were interviewed at baseline and subsequently 2, 4, 7 and 10 years after. Each examination included a complete cognitive evaluation with systematic screening of dementia. From the 2-year follow-up, 7008 non-demented participants were asked at each follow-up whether they have had a history of anaesthesia (general anaesthesia (GA) or local/locoregional anaesthesia (LRA)) since the last follow-up. The data were adjusted to take account of potential confounders such as socioeconomic status and comorbidities.

The mean age of participants was 75 years and 62% were women. At the 2-year follow-up, 33% of the participants (n=2309) reported an anaesthesia over the 2 previous years, with 19% (n=1333) reporting a GA and 14% (n=948) a LRA. A total of 632 (9%) participants developed dementia over the 8 subsequent years of follow-up, among them 284 probable AD and 228 possible AD, and the remaining 120 non-Alzheimer's dementia. The researchers found that demented patients were more likely to have received anaesthesia (37%) than non-demented patients (32%). This difference in anaesthesia was due to difference in numbers receiving general anaesthetics, with 22% of demented patients reporting a GA compared with 19% of non-demented patients. After adjustment, participants with at least one GA over the follow-up had a 35% increased risk of developing a dementia compared with participants without anaesthesia.

Dr Sztark concludes: "These results are in favour of an increased risk for dementia several years after general anaesthesia. Recognition of POCD is essential in the perioperative management of elderly patients. A long-term follow-up of these patients should be planned."