Preoperative Cognitive Performance and Postoperative Delirium Are Independently Associated With Future Dementia in Older People Who Have Undergone Cardiac Surgery: A Longitudinal Cohort Study

Abstract

Objective: To investigate if postoperative delirium was associated with the development of dementia within 5 years after cardiac surgery.

Design: Longitudinal cohort study.

Setting: Cardiothoracic Division, Umeå University Hospital, Sweden.

Patients: Patients aged 70 years old or older (n = 114) scheduled for routine cardiac procedures with cardiopulmonary bypass without documented dementia were enrolled in 2009.

Intervention: Structured assessments were performed preoperatively, 1 and 4 days after extubation, and 1, 3, and 5 years postoperatively.

Measurements and main results: Patients were assessed comprehensively, including cognitive and physical function, coexisting medical conditions, demographic characteristics, and medications. Diagnoses of delirium, depression, and dementia were made according to Diagnostic and Statistical Manual of Mental Disorders, 4th Edition, Text Revision criteria. During the 5-year period, 30 of 114 participants (26.3%) developed dementia. Postoperative delirium had occurred in 87% of those who later developed dementia. A multivariable logistic regression model showed a lower preoperative Mini-Mental State Examination score (p < 0.001; odds ratio, 0.68; 95% CI, 0.54-0.84) and the occurrence of postoperative delirium (p = 0.002; odds ratio, 7.57; 95% CI, 2.15-26.65) were associated with dementia occurrence.

Conclusions: Our findings suggest that older patients with reduced preoperative cognitive functions or who develop postoperative delirium are at risk of developing dementia within 5 years after cardiac surgery. Cognitive functions should be screened for preoperatively, those who develop postoperative delirium should be followed up to enable early detection of dementia symptoms, and management should be implemented.

Figure 1.

Flow chart of the study protocol.

Figure 2.

Mini-Mental State Examination (MMSE) scores over time in participants with and without dementia. The time axis is plotted in day and years on a log scale and reflect mean and sd. Inclusion 2009 (T1 = preoperative, T2 = postoperative day 1, T3 = postoperative day 4; mean age, 76.5 yr); 1-year 2010 (T4; mean age, 77.6 yr), 3-year 2012 (T5; mean age, 79.8 yr), and 5 years (T6; mean age, 81.6 yr) after surgery. Differences were significant (p < 0.05, t test) at all time points and decline in MMSE score over time was steeper for those with dementia (p < 0.001, generalized estimating equation analysis). Mean (sd) MMSE score, without dementia/dementia: T1 = 27.7(1.9) /25.0(3.7), T2 = 23.7(5.8)/18.1(6.4), T3 = 25.8(3.3)/20.8(5.8), T4 = 27.4 (2.3)/24.1(3.1), T5 = 27.5(2.0)/21.7(5.6), and T6 = 26.6(2.6)/17.4(6.4).

Figure 3.

Mini-Mental State Examination (MMSE) scores over time in participants with and without delirium. The time axis is plotted in day and years on a log scale and reflect mean and sd. Inclusion 2009 (T1 = preoperative, T2 = postoperative day 1, T3 = postoperative day 4; mean age, 76.5 yr); 1-year 2010 (T4; mean age, 77.6 yr), 3-year 2012 (T5; mean age, 79.8 yr), and 5 years (T6; mean age, 81.6 yr) after surgery. No significant difference was observed at T1 or T4 (p < 0.05, t test) and decline in MMSE score over time was steeper for those with dementia (p < 0.001, generalized estimating equation analysis). Mean (sd) MMSE score, no delirium/delirium: T1 = 27.4(2.3)/26.6(3.0), T2 = 26.2(2.8)/19.2(6.8), T3 = 26.7(2.8)/22.9(4.7), T4 = 27.1(2.6)/26.1(3.1), T5 = 27.2(2.8)/25.2(4.8), and T6 = 26.6(2.9)/23.1(6.2).