Chapter III. Method. sampling procedures employed, the tests used, the procedure for data

Transcription

1 98 Chapter III Method This chapter describes the research design, the sample and the sampling procedures employed, the tests used, the procedure for data collection, and the statistical analysis of the collected data. Research design A pre and post test design was used in the present research. Tests were administered in the MI patient group at pre-surgery and post-surgery. For purposes of comparison, a matched group also was selected. Tests were administered to the comparison group at base level only. Purposive sampling method was employed to select the sample. The responses were scored according to the manuals, and the data were analyzed employing appropriate statistical methods using SPSS. The findings are reported following prescribed standard procedures (APA style). Sample As stated in chapter 1, one of the main objectives of the present study is to compare the neuropsychological performances of patients with myocardial infarction (MI) with that of a healthy normal group of matched subjects. Another important objective of the study is to compare these two groups on the prevalence of Type A behavior pattern. The above objectives necessitate two sample groups: the main sample consisting of MI patients, and

2 99 a comparison sample consisting of a matched group of healthy normal subjects. Main sample. The main sample consisted of 40 patients, with a recent episode of MI, diagnosed by cardiologists, and who were scheduled for CABG. They were recruited on the basis of inclusion and exclusion criteria, from 6 hospitals in Kerala and Karnataka states, which have cardio thoracic surgery departments. They were informed about the nature of the study and were included in the sample after obtaining informed consent. In patient group the tests were administered three to four days before surgery and two weeks after coronary artery bypass graft surgery (CABG). Inclusion Criteria. Age between years Handedness: Right handed Exclusion criteria. Other major physical illnesses such as liver dysfunction, kidney dysfunction Major psychiatric and neurological disorders Clinical evidence of mental retardation Handedness: Left handed Comparison sample. A healthy normal comparison group of 40 subjects, who were matched with respect to age, education, gender, place and state of residence with the MI patient group was also selected for the study. They were drawn from the

3 100 relatives of the patients and also from the community. They were informed about the nature of the study and were included in the sample after obtaining informed consent. They were screened using the General Health Questionnaire (GHQ-12; Goldberg & Williams, 1988) for the presence of any psychiatric symptoms and those who obtained the cutoff score of two and above, were excluded from the study. Since the normal subjects were screened using GHQ for psychiatric symptoms, they were not given the depression inventory. Inclusion criteria. Age between years A score below 2 in GHQ-12 Handedness: Right handed Exclusion criteria. Any major physical illnesses such as myocardial infarction, stroke, liver dysfunction, kidney dysfunction A score of 2 and above in GHQ-12 Major psychiatric and neurological disorders Clinical evidence of mental retardation Handedness: Left handed Tools The following tools were employed in the present investigation: 1. Socio-demographic data sheet. 2. General Health Questionnaire- used for screening the

4 101 healthy normal subjects for the matched group. 3. Edinburgh Handedness Inventory-used for screening the patient group and the matched group. 4. Beck Depression Inventory- administered only among the patient group. 5. Type A/B behavior pattern scale- administered in both the patient and the matched group. 6. NIMHANS neuropsychological battery- administered in both the patient and the matched group. Socio-demographic Data Sheet. Two separate semi-structured socio demographic data sheets were prepared by the researcher, one for the comparison group and the other for the patient group. These were used to document the socio demographic characteristics of the subjects. The basic details like age, education and marital status were collected from all the subjects in the two groups (the patient group and the matched group). For the patient group, additional information related to MI, such as history of the illness, details of risk factors and information about surgery such as on/ off pump was included. General Health Questionnaire. The General Health Questionnaire (Goldberg & Williams, 1988) is a self-administered 12- item screening tool, which is used to assess the presence of diagnosable psychiatric disorders in community settings and nonpsychiatric clinical settings. This questionnaire has a total score of 12 and is

5 102 easy to administer. The tool was used in the present study to screen the healthy normal matched subjects for the absence of psychiatric symptoms. The total score ranged from 0 to 36, with higher scores indicating poor psychological well-being. A cut-off score of 2 was used (i.e., subjects getting scores of 2 and above were excluded as suggested by Renu, 2009). Reliability and validity. The internal consistency of the GHQ-12 is reported to be.90 (Hankins, 2008) and it has high validity, and is not influenced by gender, age, or level of education (Goldberg et al., 1997). Edinburgh Handedness Inventory. Neuropsychological functions are lateralized as left and right hemisphere functions. Handedness is related to the dominance of the cerebral hemispheres. In the present study handedness inventory is used to avoid the influence of cerebral dominance on neuropsychological performances. Edinburgh Handedness Inventory (Oldfield, 1971) is a simple and brief method for assessing handedness on a quantitative scale for use in neurological and other clinical and experimental work. This inventory was developed from the results obtained from the reports of 1,100 young adults. Each item of this inventory has been examined from the point of view of gender, culture and socio-economic factors related to them. It has 10 simple items which provide a quantitative measure of handedness based on hand preference for everyday activities and takes only about five to ten minutes for administration. Handedness is based on a lateral quotient. The tool was used in the present

6 103 study to screen both the MI patient group and the healthy normal matched group. Beck Depression Inventory (BDI). The Beck Depression Inventory (Beck, 1966) is one of the most widely used instruments for measuring the severity of depression. There are three versions of the BDI the original BDI, first published in 1961 and later revised in 1978 as BDI -1A, and BDI II, published in The scale used in the present study was BDI-II. It consisted 21 questions with multiple choices and is designed for individuals aged 13 years and above. The inventory is composed of items related to symptoms of depression such as hopelessness and irritability, cognitions such as guilt or feelings of being punished, as well as physical symptoms such as fatigue, weight loss, and lack of interest in sex. In the present study, the BDI was administered only to the patient group since the normal subjects were already screened for psychiatric symptoms. The participants were asked to rate how they have been feeling for the past two weeks and each answer is scored on a scale value of 0 to 3. A higher score indicates higher distress. The scale does not allow one to make a definite diagnosis of depression, but gives a dimensional representation of mood. Carney and associates used BDI score equal to or greater than 10 to diagnose depression in individuals with myocardial infarction, which revealed a moderate sensitivity (78%) and specificity (90%). Following this, in the present study a cutoff score of 10 was used to distinguish patients with depression.

7 104 Reliability and validity. The inventory is found to have high one week test-retest reliability (r=.93), suggesting that it was not overly sensitive to daily variations in mood. It also has high internal consistency (α=.91). One measure of an instrument s validity is to see how closely it agrees with another similar instrument that has been validated against clinical interview by a trained clinician. In this respect, the BDI-II is positively correlated with the Hamilton Depression Scale with a Pearson r of.71, showing good agreement. Type A/B Behavioral Pattern Scale (ABBPS). Type A/B Behavioral Pattern Scale was used to measure Type A/B behavior pattern. This scale was developed by Upinder Dhair and Manisha Jain (2001) in the Indian context to measure Type A/B behavior pattern. Unlike the other scales, this scale has two parts Form A and Form B- to measure Type A and Type B behavior patterns separately, because if a person scores high on Type A, it does not mean that he does not have any characteristic of Type B behavior pattern. There is a possibility that along with Type A characteristics the individual has some of the characteristics of Type B behavior pattern because most of the personalities have some of the characteristics of both Type A and Type B patterns. The scale constituted 33 items, 17 items in form A and 16 items in form B. Form A (Factors of Type A behavior pattern). 1. Tenseness Tenseness is the sense of time urgency (items 8, 10, 13 & 15).

8 Impatience Impatience means inability to wait calmly (items 2 & 6). 3. Restlessness Restlessness means not feeling relaxed while working (items 4, 7 &17). 4. Achievement orientation Achievement Orientation is the need to achieve something worthwhile whenever there is a possibility (3, 9 & 16). 5. Domineering Domineering is the sense of power over anything (1, 11 &14). 6. Workaholic Workaholic is one who has a tendency of doing something all the time (items 5 & 12). Form B (Factors of Type B behavior pattern). 1. Complacent Complacent behavior is the habit of enjoying everything (5, 14, 15 & 16). 2. Easygoing Easygoing is the ability to work with relaxed mood (4, 7, 12 &13). 3. Non- Assertive Non-assertive means the person is not bold enough to have attention of other persons (2 &10). 4. Relaxed Relaxed persons tend to do everything with comfort, not in hurry (1, 3 & 8).

9 Patience Patience is the ability to wait and work with ease (6, 9 & 1). There is no time limit for completing the scale. However, most respondents take about 10 minutes to complete both the forms. There are 33 statements altogether and each statement is scored on a 5-point scale (5= strongly agree; 4= agree; 3= uncertain; 2= disagree; 1= strongly disagree). Sum of the scores of Form A and Form B yields Type A and Type B scores respectively. Individuals with Type A scores within normal range and Type B scores below normal range are clear Type A persons. Individuals with Type B scores within normal range and Type A score below normal range is a clear Type B person. Individuals with either Type A scores or Type B scores above normal range and the other score within normal range are considered as either Type A s or Type B s on the basis of the higher score. Individuals with both Type A and Type B scores below normal range, above normal range, or within normal range are considered as Type AB personalities (Type A or Type B). Reliability and validity. The odd-even reliabilities of both the forms of the scale were determined and corrected for full length for a sample of 200 subjects. The reliability coefficient of form A was found to be.54 and for form B also, it was found to be.54. As all the items in the scale are concerned with personality types, the scale has high content validity, besides face validity. Judges or experts also assessed that the items of the scale were directly related to the concept of

10 107 personality types. The reliability index was calculated to find out the validity from the coefficient of reliability and it was found to be.73 for both the forms separately. The reliability index is considered to be a measure of validity (Garret,1981). NIMHANS Neuropsychological battery. The neuropsychological tests used in the present study have been taken from the NIMHANS neuropsychological battery. The battery consists of 21 different neuropsychological subtests which were originally developed by different authors and standardized in the Indian population by Rao, Subbakrishna, and Gopukumar (2004). This battery has been extensively used in researches on neuropsychological performances of a wide variety of groups including normal individuals and clinical populations, and hence has prooven validity and applicability. The different areas of functions covered in the test battery are: attention and concentration; motor speed; executive functions such as planning ability, category fluency, phonemic fluency, working memory, set shifting and response inhibition, verbal learning and memory; visual learning and memory; expressive and receptive speech; visuo-constructive ability; and focal signs. From this neuropsychological test battery, the following eight tests were used in the present investigation.

11 108 Test of speed. Digit symbol substitution test. Digit symbol substitution test (Wechsler, 1981) is a test of visuo motor co-ordination, motor persistence, information processing and speed. The test consists of a sheet in which numbers one to nine are randomly arranged in four rows of 25 squares each. The subject has to substitute each number with a symbol using a number symbol key given on top of the page. The first ten squares are for practice. The test takes about seven minutes. Administration. The subject was seated comfortably and the test sheet was placed in front of him or her. The principle of substituting symbols for digits was explained. Practice was given for the first ten squares after which the test started. The subject was instructed to complete the task as fast as possible. Scoring. The time taken to complete the test constituted the score of the test; the longer the time taken, poorer the performance. Test of attention. Digit vigilance test. Digit vigilance test (Lezak, 1995) consists of a sheet containing numbers one to nine randomly ordered and placed in rows on a page. There are 30 digits per row and 50 rows in a test sheet. The subject has to focus on target digits six and nine amongst other distracter digits. Inability to sustain and focus attention leads to increased time to complete the test.

12 109 Administration. The subject was seated comfortably and the test sheet was placed in front of the subject. The subject was asked to scan the sheet and cancel the target numbers six and nine (by drawing a / mark on them) as fast as possible without missing the targets or canceling other numbers. Scoring The time taken to complete the test formed the score; the longer the time taken, poorer the performance. Tests of executive function. Controlled oral word association test. The Controlled oral word association test (Benton & Hamsher, 1989) is a measure of phonemic fluency. In this test, the subject generates words based on phonetic similarity of words. The subject is required to generate words beginning with the letters F, A, and S for one minute. Proper nouns and names should be excluded. The same word should not be repeated with a different suffix. Subjects who do not know the English language were asked to generate words in their own mother tongue commencing with ka, pa, ma. The subject was asked to generate words for one minute in case of each letter starting with F, going unto A and ending with S or with ka, going on to pa and ending with ma as the case may be.

13 110 Administration. The subject was seated comfortably and told that he or she has to generate words beginning with a letter, which will be provided by the tester. A practice trial was given with the letter other than the ones used in the test. The subject was asked to generate as many words as possible for one minute in the case of each letter, and not to repeat the same words or give names of persons and places, and also not to say different deviations of the same word (e.g., ask, asking, asked). After each one-minute test, the subject was given a short rest pause before commencing the next test with a different letter. Scoring. The total number of acceptable new words produced in one minute was noted down for each consonant. The average of the new words generated over the three tasks formed the score; the higher the score, better the performance. Animal names test. Animal names test is a measure of category fluency (Lezak, 1995). Category fluency is another form of verbal fluency. In this test, it is the content of the words rather than the phonetic similarity of the words, which is regulated. The subject generates words which belong to a particular semantic category. The Animal names test requires the subject to generate names of animals for one minute.

14 111 Administration. The subject was asked to generate the names of as many animals as possible in one minute. He or she has to exclude the names of fish, birds and snakes. Scoring. The total number of new words generated formed the score; the higher the score, better the performance. Verbal N back test. The 1 back and 2 back versions of the N back test (Smith & Joindes, 1999) assess verbal working memory. The 1 back version requires verbal storage and rehearsal while the 2 back version requires in addition to the above, manipulation of information. Therefore, the 1 back version would involve the articulatory loop in the verbal modality and the visuo-spatial sketchpad in the visual modality. The 2 back would involve the central executive in both the modalities. Administration. Thirty randomly ordered consonants common to multiple Indian languages are presented auditorily at the rate of one per second. Nine of the 30 consonants are repeated. The consonants which are repeated are randomly chosen. In the 1 back test the subject has to respond by tapping the table whenever a consonant was repeated consecutively. In the 2 back test, the subject has to respond by tapping the table whenever a consonant was

15 112 repeated after an intervening consonant. That means, in this test there will be an intervening consonant after which the consonant might repeat. Therefore, the subject was instructed to remember each consonant till the consonant is over. A practice trial was given for the subject with four consonants wherein 1 consonant is repeated. Scoring. The number of correct responses formed the score in each test; the higher the score, better the performance. Stroop test. Stroop test measures response inhibition (Benson & Struss, 1986). It measures the ease with which a perceptual set can be shifted both to conjoin demands and suppressing a habitual response in favor of an unusual one. The prefrontal areas are essential for response inhibition. In this test, the colour names blue, green, red, and yellow are printed in capital letters on a paper. The colour of the print occasionally corresponds with the colour designated by the word. The words are printed in 16 rows and 11 columns. Administration. The stimulus sheet was placed in front of the subject. The subject was asked to read the printed words column-wise as fast as possible. The time taken to read all the 11 columns was noted down. Next, the subject was asked to read the colour in which the words were printed. The time taken to read all colours was noted down. The words were presented in the mother tongue of the subject. The test takes about 20 minutes.

16 113 Scoring The time taken to read the printed words and the time taken to read the colour of the printed words were converted into seconds. The time taken to read the printed words was subtracted from the time taken to read the colour to get the Stroop effect score; the higher the score, poorer the performance. Tests of learning and memory. Rey s auditory verbal learning test (AVLT). The Rey s Auditory Verbal Learning Test (Schmidt, 1996) adapted for different cultures by WHO (Maj et al., 1994) was adapted to suit conditions in India. Rey originally developed the test in It consists of words designating familiar objects like vehicles, tools, animals and body parts. There are two lists A and B, with 15 different words in each list. The words were translated into the five Indian languages-kannada, Tamil, Telungu, Hindi, and Malayalam. Word lists in the different languages are given in appendix. The words in list A were presented at the rate of one word per second in five successive trials. The words were presented in the same order in every trial. Each trial consisted of the presentation of all 15 words, immediately followed by recall of the same. In each trial, after the presentation of the words the subject was asked to recall the words in any order. The examiner noted down the responses verbatim in the order in which the subject gives them. On an average, recall in each trial takes about 2 minutes. After the completion of all the five trials of list A, words in list B were presented once and an

17 114 immediate recall was taken for the same. This is followed by the immediate recall from list A. The subject was given a brief rest of a few minutes and then the Stroop test which does not involve the task of recall was given. After a lapse of 20 minutes from the completion of the last recall of list A, a delayed recall of words was taken. Following delayed recall, recognition of the words in list A was tested. In recognition trial, the examiner presented the words form the recognition list one by one at the rate of one word per second and the subject was asked to identify the words from list A by saying yes or no. The number of words correctly identified formed the hits. The test takes about 30 minutes. Scoring. The number of words correctly recalled in each of the 5 trials of list A as well as the total number of words recalled over all the five trials formed the AVLT- Total score. The number of words recalled correctly in the immediate recall trial, delayed recall trial and the recognition trial formed the memory. In the recognition trial, the hits or the correct response were scored separately. The other score was Long Term Percent Retention, which was calculated by the formula: Delayed Recall Score / Trial 5 score x100; the higher the score, better the performance. Complex figure test (CFT). The complex figure test (Meyers & Meyers, 1995) consists of a complex design which is abstract in nature and cannot be named easily. This test measures visuo-constructive ability and visual learning and memory. The

18 115 figure from the complex figure is copied and subsequently recalled. Immediate and delayed memory scores are obtained. Administration. An 8.5 inch by 11 inch card containing the complex figure is placed in front of the subject. A paper of the same size of the complex figure card was placed in front of the subject. The subject was asked to copy the figure on the paper and he or she was not allowed to use rulers to draw lines, but rather draw it freehand. The subject was allowed to use eraser. The subject was asked to recall the figure twice: the first time was an immediate recall three minutes after the copying was completed, and the second time was a delayed recall 30 minutes later. For the intervening three minutes, after the subject finished copying the design and before the immediate recall, another task such as one measuring verbal fluency was given to the subject. After the lapse of three minutes another sheet of paper was placed in front of the subject and then the subject was again asked to draw the design. Following this, during the thirty minutes before the delayed recall was given, the subject was given another task and he/she was not told that the design has to be drawn after this delayed period. After thirty minutes have elapsed, another sheet of paper was placed in front of the subject and the subject was asked to draw the design again from memory. Scoring. On each of the copy, immediate recall and delayed recall trials, a score of 0, 0.5, 1 or 2 was assigned to each unit of the figure based on the accuracy

19 116 and placement criteria. The correctness of reproduction is assessed according to the scoring system given in the test manual; the higher the score, better the performance. Sensitivity and Specificity. In NIMHANS battery, the subjects who score below the 15 th percentile on the scores of accuracy are considered to have a deficit. A score above the 85 th percentile is considered as a deficit for time and error scores. So the 15 th and 85 th percentiles are taken as cut-off scores to identify deficits as these represent mean plus and minus 1 standard deviation. Validity. The factorial validity of the tests were established for literate subjects. Ten subjects in each of the gender, age and education intersections were administered all the tests. There were 120 subjects in the literate sample. Variables included in the factor analysis were chosen in such a way that the different neuropsychological domains were represented, with a ratio of variables to the number of subjects at 1: 5. A principal component analysis of the data was performed for the literate and illiterate samples separately. The analysis on the literate sample, 22 variables yielded 6 factors with eigen values more than 1 accounting for 66% of the variance. The factor, which accounted for 36% of the variance, consisted of mental speed, attention, visuo-spatial construction and visual memory, and has been named as speed of visuo- spatial processing and memory. The second factor which accounted for 8% of the variance, consisted of verbal fluency, divided attention and verbal

20 117 delayed recall, and has been named as flexibility of processing. The third factor which accounted for 6.4 % of the variance consisted of verbal and visual learning and memory, and has been termed as visual encoding of learning and memory. The fourth factor, which accounted for 5.4% of the variance consisted of verbal comprehension and verbal working memory, and has been called as verbal manipulation. The fifth factor, which accounted for 5% of the variance, consisted of lower perseverative errors and high conceptual level responses, and has been termed as mental flexibility. The sixth factor accounting for 5% of the variance consisted of adequate planning and response inhibition, and has been termed as behavioral regulation. The validity of the tests was assessed using the measures of criterion validity, wherein the profiles of patients with different clinical etiologies were compared. The clinical groups which were considered for comparison were the patients with focal lesions, patients with head injury, patients with intractable epilepsy and patients with movement disorders. Sampling and data collection procedures The population for the study was MI patients who were hospitalized as inpatients. Since the units of the population belong to different hospitals, permission to conduct the research was obtained from the ethical boards of the six different hospitals selected from Kerala and Bangalore. Purposive sampling method was employed for this study. A list of 110 patients who were diagnosed as MI by cardiologists and scheduled for CABG were identified and screened. Out of 110 MI patients, 53 patients met the inclusion criteria for

21 118 recruitment. Again out of this, 10 patients dropped out and three refused consent. Thus, the study sample consisted of 40 patients with MI. In addition to the MI patient group, a matched group of 40 normal healthy subjects was also taken for comparison. The normal subjects were drawn from the relatives of patients and also from the community. Eighty healthy normal individuals were contacted for the study. Out of this, 24 subjects were screened out using GHQ, 7 subjects dropped out, 8 subjects refused consent, and 1 subject was left handed. The remaining 40 subjects formed the healthy normal matched group. Prior to inclusion in the study, the subject s written informed consent was obtained and all the information was kept confidential. The patients were told that following a heart attack and coronary artery bypass graft surgery, one s cognitive functions may or may not be affected and the purpose of the study was to evaluate this. The patients who gave their written informed consent for participation were included in the study. They were informed that they had the right to refuse to participate in the study as well as to opt out any time during the assessment without giving reasons and by doing so they would not forfeit any benefits which would normally have been available to them. They were also informed that they will not get any monetary benefits for participation in the study. Matched group was informed that a detailed neuropsychological assessment would be carried out on them so as to obtain data against which the performance of the patient group could be compared. They were informed

22 119 that they had the right to refuse to participate in the study as well as to opt out any time during the assessment without giving reasons. They were also informed that they will not get any monetary benefits for participation in the study. Tests were administered to MI patients three to four days prior to surgery and two weeks after surgery. Tests to matched group were administered only at base level. Adequate rest pauses were given to all the participants. All the participants were assessed individually after establishing rapport between the researcher and the participant. Neuropsychological tests and Type A behavior pattern scale were administered in both the groups in the same order. The Beck Depression Inventory was administered only in the patient group since the normal subjects were already screened for psychiatric symptoms.

23 120 MI patients screened for the study n=110 Healthy normal subjects contacted n= 80 MI patients excluded from the study n= 57 Alcohol Dependence n= 26 Age > 65 years n=14 History of stroke n=15 Handedness n=2 Met inclusion & exclusion criteria n= 53 Drop out n=10 Refused consent n=3 Drop out n= 7 Refused consent n= 8 Handeness n=1 GHQ cutoff score n= 24 Study sample MI patient group n= 40 Study sample matched group n= 40 Assessments- depression; neuropsychological performance; Type A Assessmentsneuropsychological performance; Type A Figure 1 The flow chart of sample recruitment for the present study

24 121 Analysis of data The data obtained were analyzed using the following statistical tests. The statistical analyses were carried out using the statistical software SPSS Microsoft word and Microsoft excel were used to generate graphs and tables. 1. Descriptive statistics such as frequencies and percentages, and mean and standard deviation have been used to describe the demographic, clinical and neuropsychological profiles of patients with MI and the matched group. 2. Chi- Square Test: the comparison of proportion of subjects falling in the categories of Type A, Type B and Type AB behavior pattern in the patient and the matched groups were carried out using chi-square test. 3. Student s t-test (independent) : The comparison between the patient group and the matched group, and the comparison between the different patient subgroups were carried out using independent t-test. 4. Paired t test: The comparison between pre and post surgery groups of different patient subgroups were carried out using paired t-test. 5. Pearson Correlation Coefficient: The relationship among neuropsychological performances, depression, Type A and Type B scores of the patient group were carried out using simple correlation.