Postoperative Delirium Linked to Accelerated Cognitive Decline

Is postoperative delirium linked to cognitive decline? Yes, delirium is associated with a faster cognitive decline in all periods from six months to six years.

Delirium, the most common postoperative complication in older adults is associated with a 40 percent faster rate of cognitive decline, suggests Harvard Medical School researchers. The findings of the study are published in the JAMA Internal Medicine.

Among older adults who developed delirium after major elective surgery, cognitive decline over 72 months occurred at a rate of 0.14 population standard deviation (SD) units per year. This was significantly faster than the long-term cognitive decline of 0.10 population SD units per year in people who either did not develop delirium or did not undergo surgery.

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‘There is an increased possibility that delirium may predispose to permanent cognitive decline and potentially dementia.’

Whether delirium caused the faster cognitive decline or was simply a marker of people with preclinical brain disease is unknown. This also highlights the importance of delirium prevention to preserve brain health in older adults who undergo surgery.

In both surgical and nonsurgical patients, delirium has been linked with subsequent cognitive decline. A recent meta-analysis showed that people who experienced an episode of delirium were more than twice as likely to show long-term cognitive decline as those without delirium.

Researchers followed 560 community-dwelling older adults in the ongoing study that began in 2010. The mean age was 76.7, and 58% of the cohort was female; at baseline all participants were dementia-free. All participants had elective surgery -- mostly orthopedic procedures -- with an anticipated hospital stay of 3 days or longer.

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During hospitalization, delirium was assessed daily with the Confusion Assessment Method (CAM) and supported by a medical record review. Overall, 134 people (24%) developed postoperative delirium.

Developing Postoperative Delirium is Linked to Quicker Rate of Cognitive Decline

Cognitive performance was assessed with a battery of 11 tests preoperatively and at multiple time points after surgery for up to 6 years. The tests measured attention, memory, language, and executive function. The researchers evaluated an additional 119 participants as a nonsurgical comparison group to quantify learning associations with cognitive retesting.

The longitudinal cognitive change was based on general cognitive performance (GCP), a composite measure scaled so that 10 GCP points were equivalent to 1 population standard deviation. GCP scores were corrected for retest effects.

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In all patients, the average cognitive changes seen after surgery included an abrupt decline 1 month after surgery, an increase in cognitive performance 2 months after surgery, a stable period 6 to 30 months after surgery, and a steady decline 3 to 6 years after surgery. The long-term cognitive change occurred at a pace of about -1.0 GCP units (95% CI -1.1 to -0.9) per year.

In overall comparisons, the group who developed delirium (compared with those who did not) showed a significantly steeper slope of cognitive decline that approximated the slope seen among individuals who receive a diagnosis of Alzheimer's disease within 5 years.

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Importantly, information on amyloid status from cerebrospinal fluid biomarkers or amyloid imaging was not available in this study population. Thus, the associations of these variables with cognitive trajectory could not be evaluated. Further research is needed to examine whether either or both hypotheses best explains the relationship between delirium and cognitive decline.

Source-Eurekalert