Journal of
Neurology
J. Neurol. 217, 195--200 (1978)
© by Springer-Verlag 1978
Short Communications
Interactive Effects of Age and Cerebral Disease on Cognitive Performances* K. deS. Hamsher and A. L. Benton Departments of Neurology and Psychology, University of Iowa, Iowa City, Iowa 52242, USA
Summary. A battery of mental tests was given to groups of younger (16--44years) and older (48--60 years) control and cerebral diseased patients. Each patient in the younger cerebral diseased group was matched individually with an older cerebral diseased patient for type and side of lesion. Each patient with cerebral disease was matched individually with a control patient for age, educational level and sex. Differences in level of test performance related to age were generally greater for cerebral diseased than for control patients. Differences in level of test performance related to diagnostic category were generally greater for older than for younger patients. Analysis disclosed a significant overall interactive effect of age and cerebral disease on the performance of mental tests, supporting the hypothesis that acquired cerebral disease has more severe behavioral consequences in older than in younger persons. Key words: Aging - Cerebral disease - Mental test performance. Zusammenfassung. Eine Batterie psychologischer Tests wurde bei Gruppen yon jtingeren (16--44 Jahre) und ~ilteren (48--60 Jahre) KontroUpatienten und Patienten mit Hirnerkrankung angewandt. Jeder einzelne Patient in der jtingeren Gruppe mit Hirnerkrankung wurde mit einem Mteren hirnerkrankten Patienten im Hinblick auf Seite und Typ der L~ision gleichgestellt. Jeder einzelne Patient mit Hirnerkrankung wurde mit einem Kontrollpatienten im Hinblick auf Alter, Schulbildung und Geschlecht gleichgestellt. Altersunterschiede im Niveau der Testleistung waren im allgemeinen gr6Ber bei Hirnerkrankten als bei Kontrollpatienten. Unterschiede zwischen diagnostischen Kategorien im Niveau der Testleistung waren im allgemeinen gr6Ber fiir ~iltere als fiir jiingere Patienten. Die Datenanalyse zeigte einen signifikanten allgemeinen Interaktionseffekt zwischen Alter und Hirnkrankheit bei der Leistung in psychologischen Tests. Dies st0tzt die Hypothese, dab erworbene * This investigation was supported by Research Grant NS-00616 from the National Institute of Neurological and Communicative Disorders and Stroke
0340-5354/78/0217/0195/$01.20
196
K. deS. Hamsher and A. L. Benton Hirnerkrankungen schwererwiegende Folgen fiir das Leistungsverhalten bei /ilteren als bei jiingeren Personen haben.
The question with which this study was concerned is the extent to which cerebral disease may have differential effects on mental test performance in younger and older individuals. There are clinical observations which suggest that this may be the case. In addition, the findings of an earlier study on the interactive effects of age and cerebral disease on simple reaction time provided support for the hypothesis that cerebral disease has more severe behavioral consequences in older than in younger patients [5]. Some relevant clinical observations come from the field of aphasia. It is known that aphasia, acquired as a result of trauma, stroke or infection in schoolage children who have already developed language, is typically somewhat less severe and clearly less permanent than in adult patients [1, 8]. Among aphasic adults, age has been found to be related to the degree of recovery from the disorder and to response to rehabilitation, older patients generally showing a poorer outcome [9]. The findings of a recent experimental study of simple visual and auditory reaction time in older and younger cerebral diseased and control patients generated rather striking evidence of an interactive effect of age and cerebral disease on the speed of execution of high-speed responses in these patients [5]. Groups of younger (16--44 years) and older (46--60 years) patients who had been matched for type and size of cerebral lesion, and corresponding groups of younger and older control patients without evidence of cerebral disease, were compared. The retardation in reaction times (68--94 msec) shown by the older cerebral diseased patients, as compared to their controls, was significantly greater than the retardation (23--24msec) shown by the younger cerebral diseased patients as compared to their controls. Similarly, the retardation in reaction times (66--84 msec) shown by the older cerebral diseased patients, as compared to the younger cerebral diseased patients, was significantly greater than the retardation (14--20 msec) shown by the older controls as compared to the younger controls. The present study represents an extension of this line of research. It was designed to answer the question of whether the indications of an interactive effect of age and cerebral disease on performance that were found in the investigation of simple reaction time would also hold for more complex cognitive functions. Accordingly, the performances on a battery of diverse verbal and nonverbal mental tests by groups of younger and older patients, who had been matched individually for type and side of lesion, were compared to the performances of groups of younger and older control patients with respect to differences attributable to age and diagnostic category. Method
Subjects. The total sample of 40 patients with hemispheric cerebral disease, who had been seen on the neurological and neurosurgical services of the University of Iowa Hospitals, consisted of
197
Interaction of Age and Cerebral Disease Table 1. Type and side of lesion in young and old patients
Number of Pairs
Type
Hemisphere
8 7 2 1 2
Neoplasm Neoplasm Neoplasm Vascular Vascular
Right Left Bilateral Right Left
a younger group ranging in age from 20 to 44 years (mean age = 33 years) and an older group ranging in age from 48 to 60 years (mean age = 54 years). Each of the 20 patients in the younger group was matched individually with a patient in the older group for side and type of lesion (Table I). Eighteen pairs of patients were also matched for sex, the two exceptions being counterbalanced. The selection of cerebral diseased patients was restricted to those who were not aphasic, showed no signs Of psychotic disorder and did not have a history of hospitalization for psychiatric illness. Each patient with disease of the brain was matched individually with a control patient without history or evidence of disease of the brain for age (within 3 years), educational level (within 2 years) and sex. The resulting younger and older control groups were identical in mean age to the corresponding groups with cerebral disease. The two younger groups were almost identical in mean educational level (11.3 years vs. 11.5 years) as were the two older groups (9.0 years vs. 9.5 years). There were 13 men and 7 women in each of the four groups. The selection of control patients was restricted to those with diverse somatic disorders but without history or evidence of cerebral disease who showed no signs of psychotic disorder or a history of hospitalization for psychiatric illness. Tests. A battery of 14 mental tests was given to each patient. The 9 verbal tests were the Comprehension, Arithmetic Reasoning, Similarities and Digit Span subtests of the Wechsler Adult Intelligence Scale (WAIS), paragraph reading [2], written arithmetic calculation [2], paired associates verbal learning [3], a test of verbal-ideational fluency [3] and the Gorham Proverbs Test [7]. The five nonverbal tests were the Picture Arrangement and Block Design subtests of the WAIS, the Elithorn Perceptual Mazes [6], the Benton Visual Retention Test [4] and a multiple choice visual memory test [2].
Results T h e m e a n test s c o r e s o f t h e f o u r g r o u p s o f p a t i e n t s a r e shoran in T a b l e 2. It will b e seen t h a t in t h e c a s e o f e a c h test, the m e a n s c o r e s o f t h e p a t i e n t s w i t h c e r e b r a l d i s e a s e w e r e l o w e r t h a n t h e i r a g e - m a t c h e d c o n t r o l s . A g e effects w e r e s i m i l a r l y c o n s i s t e n t in t h e t w o c e r e b r a l d i s e a s e d g r o u p s . T h e m e a n s c o r e o f the o l d e r p a t i e n t s was l o w e r t h a n t h a t o f t h e y o u n g e r p a t i e n t s o n e a c h test. T h e s a m e t r e n d is e v i d e n t f o r the c o n t r o l p a t i e n t s , b u t it was n o t c o m p l e t e l y c o n s i s t e n t . T h e m e a n s c o r e o f t h e o l d e r c o n t r o l s was l o w e r t h a n t h a t o f t h e y o u n g e r c o n t r o l s o n 12 o f t h e 14 tests. T h e t w o e x c e p t i o n s w e r e the W A I S S i m i l a r i t i e s a n d P a i r e d A s s o c i a t e s L e a r n i n g tests in w h i c h a slight a n d s t a t i s t i c a l l y n o n s i g n i f i c a n t r e v e r s a l o f t h e d o m i n a n t age effect o c c u r r e d in the c o n t r o l g r o u p . T h e f o c a l q u e s t i o n o f a n i n t e r a c t i v e effect o f age a n d b r a i n d i s e a s e o n t h e test performances was evaluated statistically by a multivariate analysis of variance a s s e s s i n g t h e m a i n effects o f d i a g n o s i s a n d age a n d t h e i r i n t e r a c t i o n . B o t h the
198
K. deS. Hamsher and A. L. Benton
m a i n effect of diagnosis ( F = 5.35) a n d of age ( F = 3.13) were highly significant ( P < 0.001), i n d i c a t i n g that the test p e r f o r m a n c e s of the patients with disease of the b r a i n were generally inferior to those of the controls a n d that the test p e r f o r m a n c e s of the older patients were generally inferior to those of the y o u n g e r patients. The age by diagnosis interaction ( F = 2 . 0 1 ) was also significant ( P < 0.03), indicating that disease of the b r a i n exerted a stronger adverse effect on the p e r f o r m a n c e s of the older patients t h a n on the performances of the y o u n g e r patients. G i v e n this d e m o n s t r a t i o n of a n overall age by interaction of diagnosis, the interactive effects of age a n d cerebral disease on each test p e r f o r m a n c e was examined. It was f o u n d that the difference in performance level between the older a n d y o u n g e r cerebral diseased patients was greater t h a n that between the Older a n d y o u n g e r control patients o n 11 of the l4 tests. In three instances (WAIS C o m p r e h e n s i o n , W A I S Similarities, Paired Associates Learning) the interaction effect was significant, i.e., the age difference in the cerebral diseased groups was significantly greater t h a n the age difference in the control groups. The three exceptional tests, o n which the age differences in the two diagnostic groups were opposite to the d o m i n a n t trend, were Digit Span, written arithmetic calculation a n d controlled word association. In n o n e of these instances was the age difference in the c o n t r o l groups significantly greater t h a n the age difference in the cerebral diseased groups. Table 2. Mean test scores of control and cerebral diseased patients in two age groups Test
young
old
Cerebral diseased young old
WAIS Comprehension WAIS Arithmetic WAIS Similarities WAIS Digit Span
11.3 10.0 9.4 9.8
Paragraph Reading Written Calculation Paired Associates Learning Proverbs Controlled Word Association WAIS Picture Arrangement WAIS Block Design Perceptual Mazes Visual Retention Test Multiple Choice Visual Memory
21.0 14.8 19.4 24.1 34.6
11.1 9.9 9.5 8.9 18.5 13.4 21.0 19.3 27.7
10.5 8.6 9.1 7.3 17.2 10.6 17.4 21.9 22.8
7.7 7.5 6.7 6.8 11.5 9.7 9.3 12.5 16.0
0.001 0.001 0.013 0.001 0.001 0.001 0.001 0.01 0.001
0.018 n.s. 0.061 n.s. 0.001 n.s. 0.027 0.001 0.007
0.039 n.s. 0.042 n.s. n.s. n.s. 0.001 n.s. n.s.
9.8
8.1
9.0
6.4
0.012
0.001
n.s.
10.2 13.8 6.5 13.3
9.2 13.5 5.1 12.1
8.5 10.1 5.1 11.9
6.6 7.4 3.6 9.6
0.001 0.001 0.001 0.001
0.006 0.062 0.001 0.001
n.s. n.s. n.s. n.s.
a b c
Control
Diagnosis (control vs. cerebral disease) Age (young vs. old) Diagnosis by age interaction
Significance of differences Da Ab
Significance DXA interacti°nC
Interaction of Age and Cerebral Disease
199
Inspection of standard deviations for each group on the 14 tests showed that for 12 of the tests the variability o f the cerebral damaged groups was larger than that of their respective control groups. However, the variability of the older cerebral diseased patients exceeded that of the younger cerebral diseased patients for only four of these performances (WAIS Similarities, WAIS Digit Span, Paired Associates Learning, Perceptual Mazes). Thus the significant overall age by interaction of diagnosis could not be accounted for in terms of greater interindividual variation in the older cerebral diseased group. The correlation between age and performance level on each test was also determined. For this purpose, partial product-moment correlation coefficients, in which the effect of educational level was controlled, were computed for each combined diagnostic group (i.e., 40 control patients and 40 cerebral diseased patients). The median correlation coefficient in the control group was -0.135 while the median correlation coefficient in the cerebral diseased group was -0.275. The larger negative correlation in the cerebral diseased group may be interpreted as another indication of an interactive effect between age and disease of the brain in determining performance level. The inclusion of six subtests of the WAIS formed the basis for computing a pro-rated age-corrected IQ score for each patient. The mean IQ score of the young controls was 101.6 while that of the young cerebral diseased patients was 93.2, a difference of 8.4 IQ points. The mean IQ of the older controls was 104.2 while that of the older cerebral diseased patients was 87.6, a difference of 16.6 IQ points.
Discussion
The findings indicate a tendency for older patients with disease of the brain to be more impaired relative to younger patients with cerebral disease than are older control patients relative to younger control patients. Phrased in another way, older patients with disease of the brain show more marked cognitive defects when compared to age-matched controls than do younger patients with disease of the brain. Thus the hypothesis that cerebral insult has more severe behavioral consequences in older than in younger individuals receives additional support. Certain limitations of the study are evident. First, the older and younger patients were matched for type and side of lesion but not for either the extent of lesion or its intrahemispheric location. Future studies should provide for control of the latter variables. Second, although there was a significant overall trend toward differentially poorer performances in the older cerebral diseased groups, on a test-by-test basis, this interaction was significant for only a few performances. This raises the question of whether some abilities may be more vulnerable to the interaction effect than others. The present results do not provide a clear indication of which types of performance might be more vulnerable. It is possible that interactions between type of test and location of lesion play a role. Nevertheless, the results, when considered in conjunction with those of the earlier study on reaction time [5] on an independent sample of patients, support
200
K. deS. Hamsher and A. L. Benton
the hypothesis. It m a y also be n o t e d that the older groups, with a m e a n age of 54 years a n d a range of ages from 48 to 60 years, are more appropriately classified as middle aged rather t h a n senile. If the hypothesis generated by the findings of the two studies is correct, extension of this type of investigation to the p e r f o r m a n c e s of patients in the age range of 6 0 - - 7 0 years should yield clearer evidence of a n i n t e r a c t i o n effect.
References 1. Alajouanine, T., Lhermitte, F.: Acquired aphasia in children. Brain 88, 653--662 (1965) 2. Benton, A. L.: The fiction of the "Gerstmann Syndrome". J. Neurol. Neurosurg. Psychiat. 24, 176--181 (1961) 3. Benton, A. L.: Differential behavioral effects in frontal lobe disease. Neuropsychologia 6, 53--60 (1968) 4. Benton, A. L.: The revised Visual Retention Test: Clinical and experimental applications; 3rd ed. New York: Psychological Corporation 1974 5. Benton, A. L.: Interactive effects of age and brain disease on reaction time. Arch. Neurol. 34, 369--370 (1977) 6. Benton, A. L., Elithorn, A., Fogel, M. L., Kerr, M.: A perceptual maze test sensitive to brain damage. J. Neurol. Neurosurg. Psychiat. 26, 540--544 (1963) 7. Fogel, M. L.: The proverbs test in the appraisal of cerebral disease. J. Gen. Psychol. 72, 269--275 (1965) 8. Guttmann, E.: Aphasia in children. Brain 65, 205--219 (1942) 9. Vignolo, L. A.: Evolution of aphasia and language rehabilitation:A retrospective exploratory study. Cortex 1,344--367 (1965) Received July 29, 1977
Neurology
J. Neurol. 217, 195--200 (1978)
© by Springer-Verlag 1978
Short Communications
Interactive Effects of Age and Cerebral Disease on Cognitive Performances* K. deS. Hamsher and A. L. Benton Departments of Neurology and Psychology, University of Iowa, Iowa City, Iowa 52242, USA
Summary. A battery of mental tests was given to groups of younger (16--44years) and older (48--60 years) control and cerebral diseased patients. Each patient in the younger cerebral diseased group was matched individually with an older cerebral diseased patient for type and side of lesion. Each patient with cerebral disease was matched individually with a control patient for age, educational level and sex. Differences in level of test performance related to age were generally greater for cerebral diseased than for control patients. Differences in level of test performance related to diagnostic category were generally greater for older than for younger patients. Analysis disclosed a significant overall interactive effect of age and cerebral disease on the performance of mental tests, supporting the hypothesis that acquired cerebral disease has more severe behavioral consequences in older than in younger persons. Key words: Aging - Cerebral disease - Mental test performance. Zusammenfassung. Eine Batterie psychologischer Tests wurde bei Gruppen yon jtingeren (16--44 Jahre) und ~ilteren (48--60 Jahre) KontroUpatienten und Patienten mit Hirnerkrankung angewandt. Jeder einzelne Patient in der jtingeren Gruppe mit Hirnerkrankung wurde mit einem Mteren hirnerkrankten Patienten im Hinblick auf Seite und Typ der L~ision gleichgestellt. Jeder einzelne Patient mit Hirnerkrankung wurde mit einem Kontrollpatienten im Hinblick auf Alter, Schulbildung und Geschlecht gleichgestellt. Altersunterschiede im Niveau der Testleistung waren im allgemeinen gr6Ber bei Hirnerkrankten als bei Kontrollpatienten. Unterschiede zwischen diagnostischen Kategorien im Niveau der Testleistung waren im allgemeinen gr6Ber fiir ~iltere als fiir jiingere Patienten. Die Datenanalyse zeigte einen signifikanten allgemeinen Interaktionseffekt zwischen Alter und Hirnkrankheit bei der Leistung in psychologischen Tests. Dies st0tzt die Hypothese, dab erworbene * This investigation was supported by Research Grant NS-00616 from the National Institute of Neurological and Communicative Disorders and Stroke
0340-5354/78/0217/0195/$01.20
196
K. deS. Hamsher and A. L. Benton Hirnerkrankungen schwererwiegende Folgen fiir das Leistungsverhalten bei /ilteren als bei jiingeren Personen haben.
The question with which this study was concerned is the extent to which cerebral disease may have differential effects on mental test performance in younger and older individuals. There are clinical observations which suggest that this may be the case. In addition, the findings of an earlier study on the interactive effects of age and cerebral disease on simple reaction time provided support for the hypothesis that cerebral disease has more severe behavioral consequences in older than in younger patients [5]. Some relevant clinical observations come from the field of aphasia. It is known that aphasia, acquired as a result of trauma, stroke or infection in schoolage children who have already developed language, is typically somewhat less severe and clearly less permanent than in adult patients [1, 8]. Among aphasic adults, age has been found to be related to the degree of recovery from the disorder and to response to rehabilitation, older patients generally showing a poorer outcome [9]. The findings of a recent experimental study of simple visual and auditory reaction time in older and younger cerebral diseased and control patients generated rather striking evidence of an interactive effect of age and cerebral disease on the speed of execution of high-speed responses in these patients [5]. Groups of younger (16--44 years) and older (46--60 years) patients who had been matched for type and size of cerebral lesion, and corresponding groups of younger and older control patients without evidence of cerebral disease, were compared. The retardation in reaction times (68--94 msec) shown by the older cerebral diseased patients, as compared to their controls, was significantly greater than the retardation (23--24msec) shown by the younger cerebral diseased patients as compared to their controls. Similarly, the retardation in reaction times (66--84 msec) shown by the older cerebral diseased patients, as compared to the younger cerebral diseased patients, was significantly greater than the retardation (14--20 msec) shown by the older controls as compared to the younger controls. The present study represents an extension of this line of research. It was designed to answer the question of whether the indications of an interactive effect of age and cerebral disease on performance that were found in the investigation of simple reaction time would also hold for more complex cognitive functions. Accordingly, the performances on a battery of diverse verbal and nonverbal mental tests by groups of younger and older patients, who had been matched individually for type and side of lesion, were compared to the performances of groups of younger and older control patients with respect to differences attributable to age and diagnostic category. Method
Subjects. The total sample of 40 patients with hemispheric cerebral disease, who had been seen on the neurological and neurosurgical services of the University of Iowa Hospitals, consisted of
197
Interaction of Age and Cerebral Disease Table 1. Type and side of lesion in young and old patients
Number of Pairs
Type
Hemisphere
8 7 2 1 2
Neoplasm Neoplasm Neoplasm Vascular Vascular
Right Left Bilateral Right Left
a younger group ranging in age from 20 to 44 years (mean age = 33 years) and an older group ranging in age from 48 to 60 years (mean age = 54 years). Each of the 20 patients in the younger group was matched individually with a patient in the older group for side and type of lesion (Table I). Eighteen pairs of patients were also matched for sex, the two exceptions being counterbalanced. The selection of cerebral diseased patients was restricted to those who were not aphasic, showed no signs Of psychotic disorder and did not have a history of hospitalization for psychiatric illness. Each patient with disease of the brain was matched individually with a control patient without history or evidence of disease of the brain for age (within 3 years), educational level (within 2 years) and sex. The resulting younger and older control groups were identical in mean age to the corresponding groups with cerebral disease. The two younger groups were almost identical in mean educational level (11.3 years vs. 11.5 years) as were the two older groups (9.0 years vs. 9.5 years). There were 13 men and 7 women in each of the four groups. The selection of control patients was restricted to those with diverse somatic disorders but without history or evidence of cerebral disease who showed no signs of psychotic disorder or a history of hospitalization for psychiatric illness. Tests. A battery of 14 mental tests was given to each patient. The 9 verbal tests were the Comprehension, Arithmetic Reasoning, Similarities and Digit Span subtests of the Wechsler Adult Intelligence Scale (WAIS), paragraph reading [2], written arithmetic calculation [2], paired associates verbal learning [3], a test of verbal-ideational fluency [3] and the Gorham Proverbs Test [7]. The five nonverbal tests were the Picture Arrangement and Block Design subtests of the WAIS, the Elithorn Perceptual Mazes [6], the Benton Visual Retention Test [4] and a multiple choice visual memory test [2].
Results T h e m e a n test s c o r e s o f t h e f o u r g r o u p s o f p a t i e n t s a r e shoran in T a b l e 2. It will b e seen t h a t in t h e c a s e o f e a c h test, the m e a n s c o r e s o f t h e p a t i e n t s w i t h c e r e b r a l d i s e a s e w e r e l o w e r t h a n t h e i r a g e - m a t c h e d c o n t r o l s . A g e effects w e r e s i m i l a r l y c o n s i s t e n t in t h e t w o c e r e b r a l d i s e a s e d g r o u p s . T h e m e a n s c o r e o f the o l d e r p a t i e n t s was l o w e r t h a n t h a t o f t h e y o u n g e r p a t i e n t s o n e a c h test. T h e s a m e t r e n d is e v i d e n t f o r the c o n t r o l p a t i e n t s , b u t it was n o t c o m p l e t e l y c o n s i s t e n t . T h e m e a n s c o r e o f t h e o l d e r c o n t r o l s was l o w e r t h a n t h a t o f t h e y o u n g e r c o n t r o l s o n 12 o f t h e 14 tests. T h e t w o e x c e p t i o n s w e r e the W A I S S i m i l a r i t i e s a n d P a i r e d A s s o c i a t e s L e a r n i n g tests in w h i c h a slight a n d s t a t i s t i c a l l y n o n s i g n i f i c a n t r e v e r s a l o f t h e d o m i n a n t age effect o c c u r r e d in the c o n t r o l g r o u p . T h e f o c a l q u e s t i o n o f a n i n t e r a c t i v e effect o f age a n d b r a i n d i s e a s e o n t h e test performances was evaluated statistically by a multivariate analysis of variance a s s e s s i n g t h e m a i n effects o f d i a g n o s i s a n d age a n d t h e i r i n t e r a c t i o n . B o t h the
198
K. deS. Hamsher and A. L. Benton
m a i n effect of diagnosis ( F = 5.35) a n d of age ( F = 3.13) were highly significant ( P < 0.001), i n d i c a t i n g that the test p e r f o r m a n c e s of the patients with disease of the b r a i n were generally inferior to those of the controls a n d that the test p e r f o r m a n c e s of the older patients were generally inferior to those of the y o u n g e r patients. The age by diagnosis interaction ( F = 2 . 0 1 ) was also significant ( P < 0.03), indicating that disease of the b r a i n exerted a stronger adverse effect on the p e r f o r m a n c e s of the older patients t h a n on the performances of the y o u n g e r patients. G i v e n this d e m o n s t r a t i o n of a n overall age by interaction of diagnosis, the interactive effects of age a n d cerebral disease on each test p e r f o r m a n c e was examined. It was f o u n d that the difference in performance level between the older a n d y o u n g e r cerebral diseased patients was greater t h a n that between the Older a n d y o u n g e r control patients o n 11 of the l4 tests. In three instances (WAIS C o m p r e h e n s i o n , W A I S Similarities, Paired Associates Learning) the interaction effect was significant, i.e., the age difference in the cerebral diseased groups was significantly greater t h a n the age difference in the control groups. The three exceptional tests, o n which the age differences in the two diagnostic groups were opposite to the d o m i n a n t trend, were Digit Span, written arithmetic calculation a n d controlled word association. In n o n e of these instances was the age difference in the c o n t r o l groups significantly greater t h a n the age difference in the cerebral diseased groups. Table 2. Mean test scores of control and cerebral diseased patients in two age groups Test
young
old
Cerebral diseased young old
WAIS Comprehension WAIS Arithmetic WAIS Similarities WAIS Digit Span
11.3 10.0 9.4 9.8
Paragraph Reading Written Calculation Paired Associates Learning Proverbs Controlled Word Association WAIS Picture Arrangement WAIS Block Design Perceptual Mazes Visual Retention Test Multiple Choice Visual Memory
21.0 14.8 19.4 24.1 34.6
11.1 9.9 9.5 8.9 18.5 13.4 21.0 19.3 27.7
10.5 8.6 9.1 7.3 17.2 10.6 17.4 21.9 22.8
7.7 7.5 6.7 6.8 11.5 9.7 9.3 12.5 16.0
0.001 0.001 0.013 0.001 0.001 0.001 0.001 0.01 0.001
0.018 n.s. 0.061 n.s. 0.001 n.s. 0.027 0.001 0.007
0.039 n.s. 0.042 n.s. n.s. n.s. 0.001 n.s. n.s.
9.8
8.1
9.0
6.4
0.012
0.001
n.s.
10.2 13.8 6.5 13.3
9.2 13.5 5.1 12.1
8.5 10.1 5.1 11.9
6.6 7.4 3.6 9.6
0.001 0.001 0.001 0.001
0.006 0.062 0.001 0.001
n.s. n.s. n.s. n.s.
a b c
Control
Diagnosis (control vs. cerebral disease) Age (young vs. old) Diagnosis by age interaction
Significance of differences Da Ab
Significance DXA interacti°nC
Interaction of Age and Cerebral Disease
199
Inspection of standard deviations for each group on the 14 tests showed that for 12 of the tests the variability o f the cerebral damaged groups was larger than that of their respective control groups. However, the variability of the older cerebral diseased patients exceeded that of the younger cerebral diseased patients for only four of these performances (WAIS Similarities, WAIS Digit Span, Paired Associates Learning, Perceptual Mazes). Thus the significant overall age by interaction of diagnosis could not be accounted for in terms of greater interindividual variation in the older cerebral diseased group. The correlation between age and performance level on each test was also determined. For this purpose, partial product-moment correlation coefficients, in which the effect of educational level was controlled, were computed for each combined diagnostic group (i.e., 40 control patients and 40 cerebral diseased patients). The median correlation coefficient in the control group was -0.135 while the median correlation coefficient in the cerebral diseased group was -0.275. The larger negative correlation in the cerebral diseased group may be interpreted as another indication of an interactive effect between age and disease of the brain in determining performance level. The inclusion of six subtests of the WAIS formed the basis for computing a pro-rated age-corrected IQ score for each patient. The mean IQ score of the young controls was 101.6 while that of the young cerebral diseased patients was 93.2, a difference of 8.4 IQ points. The mean IQ of the older controls was 104.2 while that of the older cerebral diseased patients was 87.6, a difference of 16.6 IQ points.
Discussion
The findings indicate a tendency for older patients with disease of the brain to be more impaired relative to younger patients with cerebral disease than are older control patients relative to younger control patients. Phrased in another way, older patients with disease of the brain show more marked cognitive defects when compared to age-matched controls than do younger patients with disease of the brain. Thus the hypothesis that cerebral insult has more severe behavioral consequences in older than in younger individuals receives additional support. Certain limitations of the study are evident. First, the older and younger patients were matched for type and side of lesion but not for either the extent of lesion or its intrahemispheric location. Future studies should provide for control of the latter variables. Second, although there was a significant overall trend toward differentially poorer performances in the older cerebral diseased groups, on a test-by-test basis, this interaction was significant for only a few performances. This raises the question of whether some abilities may be more vulnerable to the interaction effect than others. The present results do not provide a clear indication of which types of performance might be more vulnerable. It is possible that interactions between type of test and location of lesion play a role. Nevertheless, the results, when considered in conjunction with those of the earlier study on reaction time [5] on an independent sample of patients, support
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the hypothesis. It m a y also be n o t e d that the older groups, with a m e a n age of 54 years a n d a range of ages from 48 to 60 years, are more appropriately classified as middle aged rather t h a n senile. If the hypothesis generated by the findings of the two studies is correct, extension of this type of investigation to the p e r f o r m a n c e s of patients in the age range of 6 0 - - 7 0 years should yield clearer evidence of a n i n t e r a c t i o n effect.
References 1. Alajouanine, T., Lhermitte, F.: Acquired aphasia in children. Brain 88, 653--662 (1965) 2. Benton, A. L.: The fiction of the "Gerstmann Syndrome". J. Neurol. Neurosurg. Psychiat. 24, 176--181 (1961) 3. Benton, A. L.: Differential behavioral effects in frontal lobe disease. Neuropsychologia 6, 53--60 (1968) 4. Benton, A. L.: The revised Visual Retention Test: Clinical and experimental applications; 3rd ed. New York: Psychological Corporation 1974 5. Benton, A. L.: Interactive effects of age and brain disease on reaction time. Arch. Neurol. 34, 369--370 (1977) 6. Benton, A. L., Elithorn, A., Fogel, M. L., Kerr, M.: A perceptual maze test sensitive to brain damage. J. Neurol. Neurosurg. Psychiat. 26, 540--544 (1963) 7. Fogel, M. L.: The proverbs test in the appraisal of cerebral disease. J. Gen. Psychol. 72, 269--275 (1965) 8. Guttmann, E.: Aphasia in children. Brain 65, 205--219 (1942) 9. Vignolo, L. A.: Evolution of aphasia and language rehabilitation:A retrospective exploratory study. Cortex 1,344--367 (1965) Received July 29, 1977
