Ⅵ CLINICAL INVESTIGATIONS

Anesthesiology 2008; 108:8–17 Copyright © 2007, the American Society of Anesthesiologists, Inc. Lippincott Williams & Wilkins, Inc. Type and Severity of Cognitive Decline in Older Adults after Noncardiac Surgery Catherine C. Price, Ph.D.,* Cynthia W. Garvan, Ph.D.,† Terri G. Monk, M.D., M.S.‡

Background: The authors investigated type and severity of onstrate that individuals 60 yr or older are at increased cognitive decline in older adults immediately and 3 months risk for developing cognitive impairment after major, after noncardiac surgery. Changes in instrumental activities of noncardiac surgery. To date, however, little is known daily living were examined relative to type of cognitive decline. Methods: Of the initial 417 older adults enrolled in the study, about the type of cognitive change experienced by this 337 surgery patients and 60 controls completed baseline, dis- population group. Within the disciplines of behavioral charge, and/or 3-month postoperative cognitive and instru- neurology and neuropsychology, function is typi- mental activities of daily living measures. Reliable change meth- cally subdivided into domains or systems.3 For example, ods were used to examine three types of cognitive decline: our capacity for learning and remembering is an essential memory, executive function, and combined executive function/ memory. SD cutoffs were used to grade severity of change as brain function (i.e., represents the memory domain). mild, moderate or severe. Another critical function is our ability to efficiently pro- Results: At discharge, 186 (56%) patients experienced cogni- cess information, concentrate, and self-monitor (i.e., ex- tive decline, with an equal distribution in type and severity. At ecutive function domain).4 Cognitive functions are local- 3 months after surgery, 231 patients (75.1%) experienced no ized or associated with specific brain regions (e.g., cognitive decline, 42 (13.6%) showed only memory decline, 26 (8.4%) showed only executive function decline, and 9 (2.9%) medial temporal lobe for memory; and sub- showed decline in both executive and memory domains. Of cortical network systems for executive function) and those with cognitive decline, 36 (46.8%) had mild, 25 (32.5%) differentially change with age or with aberrant brain had moderate, and 16 (20.8%) had severe decline. The com- processes, such as or stroke. With regard to bined group had more severe impairment. Executive function understanding POCD, examining the type of cognitive or combined (memory and executive) deficits involved greater levels of functional (i.e., instrumental activities of daily living) change may give us information as to which brain sys- impairment. The combined group was less educated than the tems are most vulnerable to perioperative and operative unimpaired and memory groups. events. It may also have implications for postsurgical Conclusion: Postsurgical cognitive presentation varies with rehabilitation approaches. time of testing. At 3 months after surgery, more older adults We report on a subgroup analysis of older adults en- experienced memory decline, but only those with executive or 2 combined cognitive decline had functional limitations. The rolled in a larger investigation on POCD. We hypothe- findings have relevance for patients and caregivers. Future re- sized that older adults would present with different search should examine how perioperative factors influence types of cognitive impairment at 3 months after noncar- neuronal systems. diac surgery. We analyzed the data from the study by Monk et al.2 to determine whether there were varying A COMPANION article by Monk et al. and other studies types of cognitive impairment after surgery. Because of 1,2 on postoperative cognitive dysfunction (POCD) dem- the selective nature of the tests in this study, we focused our examination of the incidence of decline on measures This article is accompanied by an Editorial View. Please see: predominantly assessing memory or executive function. ᭜ Maze M, Cibelli M, Grocott HP: Taking the lead in research The severity of cognitive decline within each of these into postoperative cognitive dysfunction. ANESTHESIOLOGY domains was labeled as mild, moderate, or severe de- 2008; 108:1–2. pending on the SD change score from baseline (1, 1.5, or 2 SDs, respectively). Type of cognitive function was also examined for different outcomes in instrumental activi- * Assistant Professor, Departments of Clinical and Health and Anesthesiology, † Research Assistant Professor, Division of Biostatistics, Univer- ties of daily living (IADLs). sity of Florida. ‡ Professor, Department of Anesthesiology, Duke University Medical Center, Durham, North Carolina. Received from the Departments of Anesthesiology and Clinical and Health Psychology, University of Florida, Gainesville, Florida. Submitted for publication Materials and Methods December 8, 2004. Accepted for publication August 7, 2007. Supported by grant Nos. K01-AG19214 and F32-AG021362 from the National Institute on Aging, The current study is a subanalysis of a larger investiga- Bethesda, Maryland; the Anesthesia Patient Safety Foundation, Indianapolis, In- tion completed by Monk et al.2 as reported in a compan- diana; and the I. Heermann Anesthesia Foundation, Gainesville, Florida. Pre- sented in part at the Annual Meeting of the American Society of Anesthesiolo- ion article. Informed written consent was obtained ac- gists, San Francisco, California, October 11–15, 2003. cording to University of Florida Institutional Review Address correspondence to Dr. Price: Department of Clinical and Health Psychology, University of Florida, P.O. Box 100165, Gainesville, Florida 32610- Board (Gainesville, Florida) guidelines and the Declara- 0165. [email protected]fl.edu. Information on purchasing reprints may be found at tion of Helsinki. From 1,064 participants in this larger www.anesthesiology.org or on the masthead page at the beginning of this issue. study, the data from 417 participants aged 60 yr or older ANESTHESIOLOGY’s articles are made freely accessible to all readers, for personal use only, 6 months from the cover date of the issue. were assessed. Of these older adult participants, 355

Anesthesiology, V 108, No 1, Jan 2008 8 TYPE AND SEVERITY OF COGNITIVE DECLINE 9 underwent major noncardiac surgeries that required a Color Word Test. Patient assignment to one of six pos- minimum of a 2-day inpatient stay (50 minimally inva- sible sequences was random. For the current study, only sive, 167 intraabdominal/thoracic, 138 orthopedic). The dependent variables that have been routinely shown to remaining 62 participants served as nonsurgical con- be either associated with executive function (involving trols. As part of the larger investigation, all participants the concepts of concentration/set-shifting/processing were asked to participate in a prospective longitudinal speed) or learning/memory functions were analyzed. study evaluating the frequency of cognitive change after The Concept Shifting Task and the Stroop Color Word major, noncardiac surgery.2 Participants were excluded Test provide two dependent variables: time to comple- from the study if they were undergoing cardiac, carotid, tion (seconds) and number of errors. Only time to com- or neurologic surgery or presented with significant cog- pletion was analyzed because it is more commonly used nitive impairment as suggested by a score of less than 24 within the neuropsychological literature and allows for on a preoperative Mini-Mental State Examination.5 Other more robust statistical analysis. exclusionary criteria included a diagnosis of central ner- vous system disorders, a current or past history of a Executive Function: Concentration/Processing psychiatric illness, taking antidepressant or antianxiety Speed/Self-Monitoring. medications, or a history of drug or alcohol abuse. To be Concept Shifting Task, part C: A version of the Trail included, participants were required to have English as Making Test13 that is used to assess mental processing their first language and be able to speak and read fluently speed, visual scanning, and the ability to ignore dis- in English. All surgery was performed with general an- tracting stimuli. Part C of the Concept Shifting Task is esthesia, and there were no restrictions on the type of analogous to Trail Making Test part B in that it requires anesthesia or postoperative analgesia. rapid alternation between letters and digits. For the current study, the dependent variable was the number Procedure and Materials of seconds required to complete the task. Each participant underwent neuropsychological test- Stroop Color Word Test, part 3: A version of the Stroop ing at three time points: up to 14 days before surgery, Color Word Test14,15 used to assess concentration and upon hospital discharge (or at 1 week after surgery if still the ability to ignore distracting stimuli. In part 3 of the hospitalized), and at 3 months after surgery. All patients Stroop Color Word Test, the participant views words completed baseline assessments of general cognitive that spell out a color but are printed in contrasting ink functioning as assessed by the Mini-Mental State Exami- colors (e.g., red is printed with blue ink). The participant nation,5 as assessed by the Beck Depression is instructed to tell the color of the ink in which the Inventory,6 current and general as assessed by words are printed rather than read the actual word. For the State Trait Anxiety Inventory,7 and pain as measured the current study, the dependent variable was the num- by a numerical pain rating scale (0 ϭ no pain; 10 ϭ ber of seconds required to complete the task. severe pain). Health status at the time of enrollment was Letter–Digit Coding: A European version of the Digit calculated using a measure of comorbidity.8 IADLs were Symbol subtest from the Wechsler Adult Intelligence assessed9 at baseline and again at 3 months after surgery Scale16 that is used to assess concentration, processing with a questionnaire that contained seven questions re- speed, and visual scanning abilities. For this test, par- lated to the use of the telephone, commuting, shopping, ticipants are required to quickly match nine letters preparation of meals, housework, medication taking, with nine different symbols within a 1-min time pe- and finances. This questionnaire was completed by both riod. For the current study, the dependent variable the patient and an informant (a member of the patient’s included the total number of symbols correctly immediate family). If a patient could do the activity without matched within the allotted 1-min time period. assistance, the score was 0; if some assistance from other people was needed to do the activity, the score was 1; and Learning and Memory. if the patient could not do the activity, the score was 2 Visual Verbal Learning: This is a visual version of the Rey (scores ranged from 0 to 14). Higher scores indicate in- Auditory Verbal Learning Test.17,18 In this test, 15 creasing difficulty in engaging in daily activities. words are individually presented in a visual format over a series of three learning trials. Each word is Neuropsychological Assessment visually shown at a rate of one word per 2 s. At the The procedures for the neuropsychological assess- completion of each trial, participants are asked to ment protocol are described elsewhere.2 The protocol immediately recall as many words as possible. This included the tests used to evaluate patients for POCD in test contains two separate recall indices that uniquely the International Study of Postoperative Cognitive Dys- assess learning and memory abilities. function 1 and 2 (ISPOCD1 and ISPOCD2).1,2,10–12 Three parallel forms of the tests were used in a sequence using Immediate recall: An index of the Visual Verbal Learn- a full Latin square design for tests other than the Stroop ing Test used to assess immediate learning ability of

Anesthesiology, V 108, No 1, Jan 2008 10 PRICE ET AL.

the 15 words presented in three separate trials. The speed cluster as an “executive function” index and the dependent variable of interest includes total num- learning/memory cluster as the “memory” index. ber of correct words recalled across all three learn- Reliable change scores were used to assess cognitive ing trials. change from baseline to discharge and then from base- Delayed recall: An index of the Visual Verbal Learn- line to 3 months for each patient undergoing surgery. ing Test used to assess retention of the learned Reliable change methods have been routinely used to words after a 15- to 25-min delay. The dependent assess changes in after neurologic surger- 19,20 variable of interest included total number of correct ies. The reliable change score for each neuropsycho- words recalled on this index. logical assessment was calculated by (1) computing the change score (difference of baseline to the postsurgery Statistical Analysis. Of the initial 417 older adults time point) for each subject, (2) finding the mean and SD enrolled in the study, 60 controls and 337 surgery pa- of change scores for the control group, and (3) standard- tients completed baseline, discharge, and/or 3-month izing the change score for surgery patients by subtract- postoperative measures. Data were processed by check- ing the mean of the control group then dividing by the ing for item nonresponse, distributional forms (e.g., nor- SD of the control group. The formula for the reliable mality of continuous data elements), and creating de- change score is Reliable Change Score ϭ ͓͑Change ͒͑ ͔͒ ͑ ͒ rived variables (e.g., measure of comorbidity, IADL Score Mean Change Scorecontrol group / SDcontrol group ]. change scores). SAS version 9.1 (SAS Institute Inc., Cary, We next formed composite scores for the executive NC) statistical software was used for all statistical analy- function and memory indices. The executive function ses. Frequencies and percents were calculated for cate- composite change score was created by averaging the gorical data, and means and SDs were calculated for reliable change scores for the executive function neuro- numerical data. Chi-square and Fisher exact tests were psychological measures (i.e., Concept Shifting Task part used to test relations between bivariate categorical data; C, Stroop Color Word Test part 3, Letter–Digit Coding). Wilcoxon rank sum and Kruskal-Wallis tests were used The reliable change scores for the memory neuropsycho- to test relations between categorical data (e.g., groups) logical measures (i.e., Visual Verbal Learning immediate and numerical measures. A chi-square goodness-of-fit test recall, Visual Verbal Learning delay recall) were averaged was used to test for equality of proportions. to create a memory composite change score. Factor analysis was used to confirm our conceptual The severity of cognitive change on each of the exec- grouping of the neuropsychological variables and to re- utive function and memory indices was graded as mild, duce the number of neuropsychological variables, thereby moderate, or severe based on the SDs of the composite decreasing the number of statistical analyses and improv- scores. Mild decline is defined as a change of 1 SD, ing cognitive domain reliability.3 Factor analysis was moderate as a change of 1.5 SDs, and severe as 2 SDs or performed using a variable clustering approach imple- greater. Patients were then classified into one of the mented with the variable cluster analysis (VARCLUS) following four mutually exclusive types: (1) no impair- ment, (2) executive function (no decline on the memory procedure in SAS. This approach combines traditional index), (3) memory (no decline on the executive func- factor analysis with hierarchical clustering to produce tion index), and (4) combined (decline in both executive scales that are simple and easy to interpret. The variable function and memory domains). cluster analysis procedure uses iterative splitting and factor analysis methods to divide a group of variables into discrete (nonoverlapping) subgroups that are rela- Results tively highly correlated. Splitting continues until a stop- ping criterion (a mathematical optimization based on As shown in table 1, the control and surgery patients eigenvalues) is reached. Data were available for 345 matched on all demographics, baseline mood, pain, and patients undergoing surgery on the five baseline neuro- general cognitive functioning abilities (Mini-Mental State psychological assessments considered in this study. Fac- Examination).5 Table 2 provides a summary of the raw, tor analysis yielded two clusters: an executive function/ standardized neuropsychological variables and reliable set-shifting/processing speed cluster (minimum proportion change scores by group (control, surgery). of variation explained by cluster was 0.56) consisting of Concept Shifting Task part C, Stroop Color Word Test Discharge Results: Type and Severity of Cognitive part 3, Letter–Digit Coding, and a learning/memory clus- Impairment ter (minimum proportion of variation explained by clus- Of 334 surgery patients who completed discharge test- ter was 0.68) consisting of Visual Verbal Learning im- ing, 148 (44.3%) did not experience a change in cogni- mediate and delayed recall. Proportion of variation tive function equal to or greater than 1 SD from baseline explained by both clusters was 0.89. For simplicity, we performance, 75 (22.5%) experienced a decline on the termed the executive function/set-shifting/processing executive function index, 61 (18.3%) experienced a de-

Anesthesiology, V 108, No 1, Jan 2008 TYPE AND SEVERITY OF COGNITIVE DECLINE 11

Table 1. Control and Surgery Baseline Demographics

Control Participants* (n ϭ 60) Surgery Participants* (n ϭ 337) P Value

Age, yr 68.3 Ϯ 5.2 69.7 Ϯ 6.8 0.2075 Sex, % Male 43 43 0.9648 Female 57 57 Years of education 13.7 Ϯ 2.7 13.4 Ϯ 2.8 0.4034 Beck Depression Inventory score 6.1 Ϯ 5.4 5.8 Ϯ 5.1 0.6850 State Trait Anxiety Index Trait anxiety 31.6 Ϯ 8.2 29.9 Ϯ 8.3 0.0866 State anxiety 36.4 Ϯ 12.8 33.2 Ϯ 11.1 0.0934 Mini-Mental State Examination 29.1 Ϯ 1.3 28.8 Ϯ 1.4 0.0775

Data are mean Ϯ SD or percent. * Had discharge and/or 3-month neuropsychological data. cline on the memory index, and 50 (14.9%) experienced performance, 26 (8.4%) experienced decline on the ex- a decline on both the executive function and memory ecutive function index, 42 (13.6%) experienced decline indices (i.e., a combined impairment). Among those with on the memory index, and 9 (2.9%) experienced decline cognitive decline at discharge, there was no difference on both the executive function and memory indices (i.e., between frequency of cognitive type (␹2 ϭ 5.06, df ϭ 2, combined group). Among those with cognitive impair- P ϭ 0.0794). ment, there was a significant difference in the frequency In addition, among those with cognitive impairment, of type of cognitive decline (␹2 ϭ 21.22, df ϭ 2, P Ͻ there was an equal distribution for severity of decline 0.0001), with more patients declining on the memory from baseline to discharge (mild [n ϭ 67, 35.8%], mod- index relative to the executive function index (P ϭ erate [n ϭ 60, 32.1%], or severe [n ϭ 60, n ϭ 32.1%] 0.0523) and more patients declining on the executive decline; ␹2 ϭ 0.52, df ϭ 2, P ϭ 0.7695). function index relative to combined index (P Ͻ 0.0041). Among those with cognitive decline, there was a sig- 3 Months after Surgery: Type and Severity of nificant difference in the proportion of patients demon- Cognitive Impairment strating mild (n ϭ 36, 46.8%), moderate (n ϭ 25, 32.4%), Of the 308 surgery patients completing cognitive test- or severe (n ϭ 16, n ϭ 20.8%) decline from baseline to ing at 3 months after surgery (tables 3 and 4), 231 3 months after surgery (␹2 ϭ 7.82, df ϭ 2, P ϭ 0.0201). (75.1%) did not experience a change in cognitive func- Pairwise comparisons identified that there were many tion equal to or greater thana1SDdecline from baseline more mildly impaired relative to severely impaired pa-

Table 2. Neuropsychological Test Raw (Baseline, Discharge, 3-Month) and Standardized Reliable Change Index Scores for the Groups (337 ؍ and Surgery (n (60 ؍ Control (n

Discharge Reliable 3-Month Reliable Baseline Discharge 3 Months Change Score Change Score

Controls n ϭ 60 n ϭ 59 n ϭ 56 Verbal Learning Test, learning trials 26.4 Ϯ 6.4 27.2 Ϯ 6.3 28.9 Ϯ 8.7 NA NA Verbal Learning Test, delay 9.2 Ϯ 3.2 8.8 Ϯ 3.4 9.8 Ϯ 3.7 NA NA Concept Shifting Task, part C, number/letter 35.6 Ϯ 10.3 35.2 Ϯ 11.1 34.2 Ϯ 11.4 NA NA task, time in seconds Letter–Digit Coding 32.6 Ϯ 6.4 33.0 Ϯ 8.4 33.0 Ϯ 6.3 NA NA Stroop Color Word Test, part 3, interference 51.4 Ϯ 13.4 46.6 Ϯ 13.2 47.5 Ϯ 13.4 NA NA task, time in seconds Surgery patients n ϭ 337 n ϭ 334* n ϭ 308 n ϭ 334 n ϭ 308 Verbal Learning Test, immediate, total 25.6 Ϯ 6.0 23.7 Ϯ 6.6 26.5 Ϯ 6.1 Ϫ0.5 Ϯ 1.2 Ϫ0.3 Ϯ 0.9 correct across three learning trials Verbal Learning Test, delay, total words 8.3 Ϯ 3.1 6.7 Ϯ 3.2 8.4 Ϯ 3.2 Ϫ0.5 Ϯ 1.3 Ϫ0.2 Ϯ 1.0 correct after filled time delay Concept Shifting Task, part C, number/letter 40.9 Ϯ 15.7 48.1 Ϯ 22.9 40.0 Ϯ 17.4 Ϫ0.9 Ϯ 2.3 0.0 Ϯ 1.8 task, time in seconds Letter–Digit Coding, total correct in 60 s 29.0 Ϯ 7.4 25.4 Ϯ 7.4 30.3 Ϯ 7.2 Ϫ0.6 Ϯ 0.9 0.1 Ϯ 1.2 Stroop Color Word Test, part 3 (interference 56.3 Ϯ 15.8 61.1 Ϯ 22.2 53.4 Ϯ 16.9 Ϫ1.1 Ϯ 2.0 Ϫ0.1 Ϯ 1.7 task), time in seconds

Data are mean Ϯ SD. * 333 completed all seven indices as reported in Monk et al.2 NA ϭ not applicable.

Anesthesiology, V 108, No 1, Jan 2008 12 PRICE ET AL.

Table 3. Summary Statistics of Reliable Change Index by 3-Month Cognitive Type

Standardized Composite Change Score

No Decline (n ϭ 231) Executive Decline (n ϭ 26) Memory Decline (n ϭ 42) Combined Decline (n ϭ 9)

Verbal Learning Test, learning trials Ϫ0.1 Ϯ 0.8 Ϫ0.0 Ϯ 0.8 Ϫ1.5 Ϯ 0.6 Ϫ1.3 Ϯ 0.2 Verbal Learning Test, delay total 0.1 Ϯ 0.8 0.2 Ϯ 0.8 Ϫ1.7 Ϯ 0.8 Ϫ1.8 Ϯ 0.9 Concept Shifting Task, part C 0.3 Ϯ 1.5 Ϫ2.2 Ϯ 2.2 Ϫ0.0 Ϯ 0.9 Ϫ2.5 Ϯ 3.9 (number/letter task), s Letter–Digit Coding, total 0.3 Ϯ 1.2 Ϫ0.6 Ϯ 0.9 0.2 Ϯ 1.0 Ϫ1.8 Ϯ 2.1 Stroop Color Word Test, part 3 0.1 Ϯ 1.3 Ϫ1.9 Ϯ 2.5 0.2 Ϯ 1.7 Ϫ2.6 Ϯ 3.4 (interference task), s

Ϯ ϭ Ϫ Data are mean SD, calculated using a reliable change score formula: Reliable Change Score [(Change Score) (Mean Change Scorecontrol group)]/(SDcontrol group)]. tients (P ϭ 0.0055), with all other comparisons statisti- patients demonstrating primary memory decline at dis- cally equal. charge, 3 (4.9%) did not complete follow-up testing, 42 There was a significant cognitive type by severity type (68.9%) no longer exhibited any decline at follow-up, 3 interaction (␹2 ϭ 23.16, df ϭ 4, P ϭ 0.0001; table 4). (4.9%) changed to executive function, 12 (19.7%) re- Groups differed by classification of impairment, with mained memory, and 1 (1.6%) changed to combined. Of executive function and memory groups having more the 50 patients demonstrating a combined decline at patients classified as mildly impaired rather than severely discharge, 2 (4.0%) did not complete follow-up testing, impaired and the combined group having more patients 29 (58.0%) no longer exhibited any decline at follow-up, classified as severely impaired rather than mildly im- 2 (4.0%) changed to executive function, 11 (22.0%) paired (Fisher exact test, P ϭ 0.0202). changed to memory, and 6 (12.0%) remained combined (table 5). Cognitive Type and Failure to Complete 3-Month Testing 3-Month Cognitive Type and Demographic, Mood, A set of 29 patients who completed discharge testing Pain, and Surgery Variables did not complete testing at 3 months after surgery. Of Three-month cognitive types (no impairment, execu- these 29 patients, 14 (48.3%) had not exhibited any cog- tive function, memory, combined) were compared on nitive decline at discharge, 10 (34.5%) had declined on baseline demographics, mood, pain, surgery, and anes- the executive function index, 3 (10.3%) had declined on thesia variables (tables 6 and 7). Of the demographic the memory decline, and 2 (6.9%) had a combined ex- variables, the individuals with a decline on the combined ecutive function and memory decline at discharge. No index had lower levels of education than the no impair- difference was found between groups on the number of ment group (P value ϭ 0.0039) and the memory group patients who had died, were unable to complete testing, (P ϭ 0.0160). Baseline Mini-Mental State Examination or refused further participation (table 5). scores were statistically different among the groups; however, these differences were minimal and not likely Change in Cognitive Type from Discharge to to be clinically significant. There were no significant 3-Month Testing differences in baseline mood, general cognitive, pain, or Of the 75 patients demonstrating primary executive general surgery variables among the groups. function decline at discharge, 10 (13.3%) did not com- plete follow-up testing, 45 (60.0%) no longer exhibited Living Placement at 3 Months any decline at follow-up, 13 (17.3%) remained classified Of the 308 patients who completed 3-month testing, 2 as executive function, 6 (8.0%) changed classification to of 42 individuals (4.8%) with a memory decline and 2 of memory, and 1 (1.3%) changed to combined. Of the 61 9 individuals (22.2%) with a combined executive func-

Table 4. Raw Number (%)* Distribution of Executive Function, Memory, or Combined Cognitive Types by Severity of Cognitive Change from Baseline to 3 Months after Surgery

Executive Decline Memory Decline Combined (Memory No Decline (Memory Not Impaired) (Executive Not Impaired) and Executive Decline) Total

Mild† 13 (4.2) 22 (7.1) 1 (0.3) 36 (11.7) Moderate‡ 9 (2.9) 13 (4.2) 3 (1.0) 25 (8.1) Severe§ 4 (1.3) 7 (2.3) 5 (1.6) 16 (5.2) Total 231 (75.1) 26 (8.4) 42 (13.6) 9 (2.9) 308

* Percentages reflect frequency relative to the entire sample of 308 surgery patients. † Mild impairment ϭ decline of 1–1.5 SDs from baseline performance. ‡ Moderate impairment ϭ decline of 1.5–2 SDs from baseline performance. § Severe impairment ϭ decline of 2 SDs or more from baseline performance.

Anesthesiology, V 108, No 1, Jan 2008 TYPE AND SEVERITY OF COGNITIVE DECLINE 13

Table 5. Raw Number (%)* Distribution of Executive, Memory, or Combined Cognitive Types by Discharge and 3 Months after Surgery

Status 3 Months after Surgery

Executive Impairment Memory Impairment Combined (Memory Data Missing (Memory Not Impaired) (Executive Not Impaired) and Executive Impaired) Status after Discharge at Time Point No Impairment (n ϭ 26) (n ϭ 42) (n ϭ 9)

Data missing 0 (0) 3 (0.9) 0 (0) 0 (0) 0 (0) No impairment 14 (4) 112 (33) 8 (2) 13 (4) 1 (0.3) Executive impairment (memory 10 (3) 45 (13) 13 (4) 6 (2) 1 (0.3) not impaired) (n ϭ 75) Memory impairment (executive not 3 (0.9) 42 (12) 3 (0.9) 12 (4) 1 (0.3) impaired) (n ϭ 61) Combined (memory and 2 (0.6) 29 (9) 2 (0.6) 11 (3) 6 (2) executive impaired) (n ϭ 50)

* Percentages reflect frequency relative to the entire sample of 337 surgery patients. tion–memory decline had been moved to a residential After controlling for baseline IADL reports, there were living center. All other patients and nonsurgical controls significant differences in caregiver/informant observa- continued living at home (no statistics were completed tions of postsurgery IADL function based on patient ϭ ϭ because of small cell sizes). cognitive type (F3,264 5.37, P 0.0013). Follow-up Tukey post hoc analyses identified that the informants of the combined type identified significantly more postop- Type of Cognitive Decline and Instrumental erative IADL dysfunction relative to the executive func- Activities of Daily Living tion (P ϭ 0.0195), memory (P ϭ 0.0005), and intact Regarding patient reports, cognitive types differed signif- groups (P ϭ 0.0048). This difficulty was significant icantly on IADL function after controlling for baseline IADL among six of the seven IADL items (all P Ͻ 0.01). Of ability (F ϭ 5.84, P ϭ 0.0007). Follow-up Tukey post 3,299 these groups, informants for the memory group reported hoc analyses identified that executive and combined the least amount of problems at this time point. groups experienced greater postsurgery IADL dysfunction relative to the memory group (P ϭ 0.0032 and P ϭ 0.0096, respectively; table 8). IADL item analysis suggests that the Discussion executive function group, followed by the combined group, required more postoperative assistance with six of As an extension to the study conducted by Monk et the seven IADL items (all P Ͻ 0.01; table 9). al.,2 we examined type and severity of noncardiac post-

Table 6. Demographic, Mood, General Cognitive, Pain, and Surgery Variables by Cognitive Type (No Impairment, , Memory, Combined)

Executive Memory Combined No Impairment Impairment Impairment Impairment (n ϭ 231) (n ϭ 26) (n ϭ 42) (n ϭ 9) P Value

Age, yr 69.3 Ϯ 6.4 71.7 Ϯ 7.4 68.8 Ϯ 6.3 71.8 Ϯ 7.3 0.2281 Sex, % 0.8772 Male 76.7 7.5 13.5 2.3 Female 73.7 9.1 13.7 3.4 Years of education 13.7 Ϯ 2.9 12.7 Ϯ 2.3 13.5 Ϯ 2.4 11.0 Ϯ 2.5 0.0078 Beck Depression Inventory score 5.5 Ϯ 4.8 6.8 Ϯ 5.4 5.1 Ϯ 5.1 7.8 Ϯ 5.7 0.2846 State Trait Anxiety Index Trait anxiety 29.5 Ϯ 8.1 33.3 Ϯ 8.5 28.3 Ϯ 6.9 32.6 Ϯ 7.9 0.0540 State anxiety 32.8 Ϯ 10.7 36.0 Ϯ 14.3 30.7 Ϯ 8.8 33.4 Ϯ 8.7 0.6117 Mini-Mental State Examination score 28.9 Ϯ 1.4 28.3 Ϯ 1.6 28.8 Ϯ 1.3 29.7 Ϯ 0.7 0.0452 Visual analog pain score 2.5 Ϯ 3.1 2.7 Ϯ 3.3 2.1 Ϯ 2.7 2.8 Ϯ 3.1 0.9005 ASA physical status, % 0.1059 I 76.5 0.0 23.5 0.0 II 79.1 4.6 13.7 2.6 III 68.5 14.6 13.1 3.9 IV 100.0 0.0 0.0 0.0 Charlson Comorbidity Index 1.9 Ϯ 2.1 2.4 Ϯ 2.2 2.1 Ϯ 2.1 1.5 Ϯ 1.0 0.6168

Data are mean Ϯ SD or percent. ASA ϭ American Society of Anesthesiologists.

Anesthesiology, V 108, No 1, Jan 2008 14 PRICE ET AL.

Table 7. Surgical Procedure and Hospital Stay by 3-Month Cognitive Type

No Impairment Executive Impairment Memory Impairment Combined Impairment (n ϭ 231) (n ϭ 26) (n ϭ 42) (n ϭ 9) P Value

Type of surgery 0.6965 Minimally invasive* 81.0 4.8 9.5 4.8 Intraabdominal/thoracic 72.4 8.0 16.7 2.9 Orthopedic 75.8 10.2 11.7 2.3 Duration of anesthesia, min 214.1 Ϯ 112.1 195.1 Ϯ 89.4 207.9 Ϯ 88.2 177.7 Ϯ 48.1 0.6736 ICU stay 0.2835 No ICU stay 74.0 9.5 13.0 3.5 Yes ICU stay 79.6 3.7 16.7 0.0 Duration of hospital stay, days 5.3 Ϯ 5.4 5.0 Ϯ 2.7 4.6 Ϯ 3.1 4.4 Ϯ 1.1 0.9461

Data are mean Ϯ SD or percent. * Minimally invasive surgery included laparoscopic surgery and superficial reconstructive surgery. ICU ϭ intensive care unit. operative cognitive difficulty among adults aged 60 yr or small set of executive function (8%) and a large set of older with three neuropsychological composite indices combined patients (22%) converted to memory impair- labeled as executive function, memory, and combined ment at 3 months. Very few patients (5% from the (representing a decline on both executive function and memory, 4% from the combined) converted into the memory indices). Our findings indicate that postopera- executive function or combined group. These findings tive cognitive presentation and severity varies with time indicate that, of the three cognitive groups, individuals of testing and has functional relevance. diagnosed with memory impairment at discharge were more likely to remain in the investigation and continued Type and Severity of Cognitive Presentation by to experience this primary memory impairment at 3 Time Point months after surgery. Individuals with executive dys- At hospital discharge, there was an equal distribution function at discharge, by contrast, were more likely to of cognitive impairment in executive function, memory, drop out from further testing. Executive function impair- and combined groups, with the severity of cognitive ment results in a fundamental problem with decline also evenly distributed among mild, moderate, or and organizational skills, both of which are important in severe impairment. In contrast, at 3 months after sur- making sure a subject returns for a follow-up appoint- gery, many more patients were impaired on the memory ment.21 This may explain the higher dropout rate among index (54%) relative to the executive function (34%) or patients with executive function impairment. For those combined (12%) indices. In the majority of patients with with more global “combined” cognitive impairment, dif- memory or executive decline, the impairment was mild ficulties with executive dysfunction seemed to resolve, in severity, whereas patients with a combined executive leaving behind only memory dysfunction at 3 months. function–memory disturbance at 3 months were more Dropout from discharge to 3 months was not com- likely to experience a severe cognitive impairment. pletely dependent, however, on whether a person had Dropout and changes in cognitive classification from cognitive impairment at discharge. Of the 29 patients discharge to 3 months seem to explain the dominance of who did not complete follow-up 3-month testing, 48% memory impairment at 3 months after surgery. Of the 29 included patients who were cognitively intact at dis- people who dropped out after discharge testing, three charge. Among those who dropped out between dis- times as many executive function patients (35%) did not charge and 3 months, just as many cognitively intact complete the 3-month follow-up relative to that of the patients experienced death between discharge and 3 memory (10%) or combined (7%) groups. In addition, a months or declined further participation at 3 months.

Table 8. Total Instrumental Activity of Daily Living* Score by Cognitive Type for Baseline and 3-Month Time Points

No Impairment Executive Impairment Memory Impairment Combined Impairment

Patient Baseline 0.53 Ϯ 1.27 1.20 Ϯ 1.68 0.36 Ϯ 0.91 0.78 Ϯ 0.83 3 months 1.18 Ϯ 1.82 2.44 Ϯ 2.31 0.44 Ϯ 0.78 3.11 Ϯ 4.07 Informant Baseline 0.82 Ϯ 1.90 1.08 Ϯ 1.56 0.44 Ϯ 0.94 0.78 Ϯ 0.83 3 months 1.38 Ϯ 2.12 1.81 Ϯ 2.77 0.54 Ϯ 0.90 4.63 Ϯ 4.47

Data are mean Ϯ SD. * Possible score range: 0–14.

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Table 9. Number (%) Requiring Assistance* in Activities of Daily Living by Cognitive Type at 3 Months

Activity of Daily Living No Impairment Executive Impairment Memory Impairment Combined Impairment P Value†

Telephone 2 (1) 0 (0) 0 (0) 0 (0) — Commute/travel 47 (20) 9 (36) 3 (7) 3 (33) 0.0049 Shopping 33 (19) 11 (44) 1 (2) 3 (33) Ͻ0.0001 Meal preparation 36 (16) 8 (32) 2 (5) 2 (22) 0.0017 Housework 90 (39) 18 (72) 11 (27) 7 (78) Ͻ0.0001 Medicine 6 (3) 3 (12) 0 (0) 1 (11) 0.0410 Finances 14 (6) 4 (16) 0 (0) 2 (22) 0.0035

* By patient report. † Comparison of impaired groups only.

This suggests that while executive function impairment believe that the findings of Monk et al. may partially initially seems to be a more risky diagnosis for dropout reflect the distribution of cognitive type within their relative to the other two groups in our sample, postdis- patient sample (i.e., more memory impairment than charge difficulties still occurred even when there was no other forms). We do not know the pattern of cognitive evidence of acute cognitive impairment. impairment in the ISPOCD1 study. Therefore, we can only speculate that the cognitive distribution in the Instrumental Activities of Daily Living ISPOCD1 study may largely reflect a decline that in- Our study demonstrates that the type of cognitive cludes executive function or combined disturbances, decline at 3 months after surgery has functional signifi- because executive function disturbance is more synon- cance for older adults. In our cognitively impaired sam- ymous with IADL dysfunction. ple, memory impairment was most common, but these Three-month cognitive types were also examined for individuals had the least amount of functional impair- differences in demographic, mood, baseline general cog- ment on IADLs according to both patients and their nitive status (i.e., Mini-Mental State Examination), pain informants. The executive function and combined level, and surgery variables. We identified group differ- groups, in contrast, had the most severe decline in IADL ences in education; individuals with combined execu- function and reported needing minimal to complete as- tive–memory impairment were significantly less edu- sistance for six of the seven IADL abilities (i.e., commut- cated than the other two cognitive impairment types. ing, shopping, meal preparation, housework, medicine, Monk et al. report that lower educational level predicted finances). The caregivers of patients with combined im- the incidence of POCD at 3 months after noncardiac pairment (both executive function and memory difficul- surgery. Our further analysis of the elderly patients in the ties) corroborated the increased IADL difficulties. study of Monk et al. indicates that lower educational These findings support the current knowledge about level seems to be not only a risk factor for developing IADLs and cognitive function in normal aging and the POCD but also a possible risk factor for developing more dementia population. Many investigators have identified global cognitive impairment when measured by neuro- that greater executive dysfunction, not memory dysfunc- psychological measures. Although reasons for the pro- tion, has been independently associated with IADL de- tective effect of education are not fully known, possible cline among intact and moderately demented adults.22–25 explanations include the concept of cognitive re- The presence of combined executive decline and mem- serve27,28 and associated factors of better test-taking abil- ory decline has been associated with declines on more ity, social support, and better postoperative medical basic activities of daily living (e.g., grooming).26 This may care. Our comparison of baseline cognitive variables explain why, within our investigation, change in IADL between groups did reveal a statistical difference on a status was most noted among the caregivers of patients general cognitive status examination (Mini-Mental State with combined impairments (both memory and execu- Examination), but the findings have little clinical signif- tive function disturbances). Therefore, impairments on icance because all groups performed well within what is combined memory and executive function domains not considered to be the normal range.3 only implicate a more severe cognitive disturbance but also poorer functional status at home. Future Clinical and Research Implications Our findings may help to clarify conflicts in the litera- The collective findings have clinical and research im- ture regarding the relation between IADL and POCD. plications. Older adult communities continue to grow in The ISPOCD1 study identified a significant correlation number throughout the country. As life expectancy in- between declines in IADL scores and cognitive dysfunc- creases, it is projected that “quality-of-life” surgeries (i.e., tion at 3 months after surgery.1 The companion article joint replacement surgery) in addition to health urgency by Monk et al.,2 however, did not find a relation be- surgeries will increase. Given that older adults have been tween the occurrence of POCD and declines on IADLs at shown to have longer-lasting cognitive impairment after 3 months after surgery. Based on our study results, we major surgeries and potentially that postsurgical cogni-

Anesthesiology, V 108, No 1, Jan 2008 16 PRICE ET AL. tive impairment may herald greater mortality,2 it is par- As the time after surgery increases, these external vari- amount that we continue pursuing more in-depth exam- ables should resolve, providing a more accurate picture inations into the treatment and mechanisms that result in of cognitive function. This seems to be true for our postoperative cognitive impairment. Understanding the current sample. By 3 months we clearly identified two etiology of cognitive types may help to develop strate- important patterns: Memory disturbance was promi- gies for preventing POCD. It is known from traumatic nent, and individuals with executive function distur- brain injury and stroke research that the type of cogni- bance had the more severe functional limitations. A tive impairment influences inpatient and rehabilitation limitation, we acknowledge, is that we classified mem- strategies.29,30 The same may hold true for different ory impairment with the composite measure of the im- types of postoperative cognitive impairment. Further- mediate and delayed indices from one test. To increase more, research on types of cognitive impairment may the robustness of a memory assessment and the reliabil- inform us about which brain systems are more vulnera- ity of a composite, we urge future investigators to at- ble to perioperative events. tempt to replicate our findings with two or more tests of Some may question our differentiation of executive memory. function from that of memory. Although we agree that To our knowledge, this is the first study to specifically executive function and memory systems are intimately examine cognitive subtypes of postoperative cognitive related (i.e., aspects of executive function are required complications. Our findings indicate that postoperative for a person to effectively learn and retrieve informa- cognitive presentation varies with the time of testing and tion), there is substantial literature supporting dissocia- has functional relevance for the patient and caregiver. tions between the two cognitive functions from a neu- These findings require replication. Future examinations roanatomical perspective. Executive function, although within larger samples should be conducted to determine multifactorial (as exemplified by the overlapping terms which neuronal systems are most influenced by periop- such as concentration, selective attention, set-shifting, erative factors. self-monitoring, processing speed), is most commonly associated with the frontal cortex,31,32 subcortical nuclei, The authors thank Maria T. van der Aa, M.S. (Research Assistant, University of 33,34 Florida, Gainesville, Florida), for her assistance with data collection and coordi- and white matter fibers. Memory functions, in con- nation of the research protocol. trast, have been classically associated with three neuro- anatomic regions within the brain (and the pathways that interconnect them). These include the medial tem- References poral lobe (, entorhinal cortex),35–37 the 38 1. Moller JT, Cluitmans P, Rasmussen LS, Houx P, Rasmussen H, Canet J, (dorsomedial, anterior nuclei), and the basal Rabbitt P, Jolles J, Larsen K, Hanning CD, Langeron O, Johnson T, Lauven PM, forebrain, which innervates the hippocampus with es- Kristensen PA, Biedler A, van Beem H, Fraidakis O, Silverstein JH, Beneken JE, 39,40 Gravenstein JS: Long-term postoperative cognitive dysfunction in the elderly sential cholinergic neurons. Disruption to any of ISPOCD1 study. ISPOCD investigators. International Study of Post-Operative these brain systems can occur during perioperative Cognitive Dysfunction. Lancet 1998; 351:857–61 2. Monk TG, Weldon BC, Garvan CW, Dede DE, van der Aa MT, Heilman KM, events. 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