Clinical validity of NIMHANS neuropsychological battery for elderly: A preliminary report.

BACKGROUND: Neuropsychological assessment plays a crucial role in the assessment of cognitive decline in older age. In India, there is a dearth of culturally appropriate standardized measure to assess cognitive functions in early dementia. The aim of the study was to examine clinical validity of NIMHANS Neuropsychological Battery for Elderly (NNB-E) in identifying early dementia.
OBJECTIVES: To examine validity (discriminant and concurrent) of NIMHANS Neuropsychological Battery for Elderly (NNB-E).
RESULTS: Participants with AD showed significantly poorer performance on every test including memory and non-memory domains. However, tests of episodic and semantic memory were particularly sensitive in discriminating between normal and AD groups. Further scores on various subtests in the NNB-E were positively associated with scores on HMSE and negatively associated with Clinical Dementia Rating and Everyday Abilities Scale for India (EASI) scores.
CONCLUSIONS: NNB-E was able to differentiate normal controls from AD patients, and it can therefore be an ecologically valid tool for Indian older adults.

INTRODUCTION

Cognitive decline is a major concern in aging and dementia research. Neuropsychological assessment is considered as crucial in identifying cognitive decline associated with dementia and related disorders.[12] Cognitive decline is often identified by culturally appropriate neuropsychological assessment. This is particularly true for country such as India, which has majority of the population from rural regions with low literacy levels and 122 local languages (234 mother tongues).[3] There is a dearth of indigenously developed neuropsychological test battery that is suitable for Indian older adults to assess cognitive function as well as decline,[4] and the need for developing and validating cognitive measures has been highlighted by several researchers.[56] To the best of our knowledge, there are very few standardized neuropsychological test batteries with culturally appropriate materials to identify early Alzheimer's disease (AD) from age-associated cognitive decline. Recently, NIMHANS Neuropsychological Battery for Elderly (NNB-E) has been developed and standardized on Indian population.[7] The present study is an attempt to examine the effectiveness of NNB-E in discriminating patients with AD from normal. The second aim of the study was to examine the concurrent validity of NNB-E.

MATERIALS AND METHODS

Sample

The study sample consisted of 99 participants (39 patients with AD and 60 normal controls) within an age range of 55-87 years. Patients with AD were selected from the Geriatric Clinic, Outpatient Department, NIMHANS, Bangalore. Inclusion criteria for AD were as follows: Age >55 years; definite cognitive decline indicated by Hindi Mental Status Examination (HMSE); Clinical Dementia Rating (CDR) of 1 or <2; Diagnosis of Alzheimer's Dementia according to DSM-IV and National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA). Patients with AD were excluded if they had a history of neurological/neurosurgical/psychiatric illness (including substance dependence other than nicotine) other than dementia of Alzheimer's Type.

The healthy normal controls were recruited from the community who were living independently in terms of their daily activities. The normal control group was free from neurological and psychiatric illness.

Instruments

Socio-demographic data sheet

A basic datasheet was administered to collect socio-demographic details of each subject included in the sample such as age, sex, date of birth, language, income, address, urban/rural, presence or absence of known physical, neurological or psychiatric illness, past psychiatric/neurological consultation, medication history, and presence of any physical problem.

Hachinski ischemic scale

The Hachinski Ischemic Scale[8] accounts for factors associated with vascular development of dementia. A score lower than 4 renders a diagnosis of AD, whereas a score of greater than 7 is classified as multi-infarct dementia.

Everyday Abilities Scale for India

This is a 12 items brief measure of activities of daily living, with norms,[9] and is appropriate for use in evaluating dementia (along with other tests) in elderly people in India.

Hindi mental-status examination

HMSE[10] is developed by Ganguli et al., (1995) and used in Indo-US cross national dementia epidemiological study. Hindi mental-status examination (HMSE) is a modified version of MMSE and is validated for Indian population.

Edinburgh handedness inventory

Edinburgh handedness inventory[11] was used to determine handedness. This inventory has a brief and a simple method of assessing handedness on a quantitative scale for use in neurological and other clinical and experimental work.

NNB-E

NNB-E is a comprehensive battery developed for assessing cognitive functions in Indian older adults.[7] It is a brief battery that takes 60 min to administer and consists of measures of attention, memory, executive functions, language, visuo-spatial construction, and parietal focal signs. Test included in the battery are a Word List, Story Recall Test (memory of logical passage), Stick Construction Test for visuo-spatial construction with immediate and delayed recall for visual memory, Digit Span, Corsi block-tapping test (working memory), Category fluency, Go/No-Go, Picture cancellation for sustained attention, and Parietal focal signs (agnosia/apraxia/body schema disturbances/left right disorientation/acalcuila).

NNB-E and screening measures were administered by the first author to all participants individually. Written informed consent was obtained from all participants and the purpose of the research was explained to each subject.

Statistical Package for the Social Sciences (SPSS 12.0) was used to analyse the obtained data. Discriminant validity of Neuropsychological Test Battery was examined using t-test. Further receiver operating characteristic (ROC) curve was used to examine the discriminating power of different neuropsychological tests to discriminate patients from normal controls. Pearson correlation coefficient was used to examine concurrent validity. For all the statistical tests, P<0.05 were considered as statistically significant.

RESULTS

Thirty-nine patients with AD and 60 normal controls participated in the present study. The mean age, education, HMSE, CDR scores, and percentages of gender and handedness are shown in Table 1. There were no significant differences between the groups on age, gender, and years of education. Patients with AD performed significantly worse on all the subtest of the neuropsychological battery as compared with healthy normal controls [Table 2]. Patients with AD showed significantly poorer performance on Word List, Story Recall Test, Fluency, Digit Span, Spatial Span, Stick Construction Test, and Go/No-Go. Further ROC curve [Figure 1] revealed that Word List-delayed recall (AUC=0.99; 95% CI, 0.97-0.99) had the highest discriminability, followed by animal fluency (AUC=0.99, 95% CI, 0.96-0.99), Stick Construction Test (0.95, 95% CI, 0.90-0.99), and Story Memory Test (0.94, 95% CI, 0.84-0.98).

Table 1

Demographic data

Table 2

Comparison of performance between NC and AD groups

Figure 1

Area under the curve for normal control and AD group

The relationship between NNB-E and dementia ratings tests was examined in order to establish concurrent validity. The results [Table 3] showed that NNB-E was significantly correlated with dementia rating tests (CDR, EASI, HMSE, P<0.05). Scores on all the subtests of NNB-E were significantly correlated in a positive direction with HMSE scores (r=0.42-0.73). Scores on NNB-E were negatively correlated with CDR (r=−0.27-0.88) and EASI scores (−0.21-0.53).

Table 3

Correlations between NNB-E and screening measures

DISCUSSION

It is argued that culturally appropriate, sensitive, and specific tests reflect true cognitive performance, particularly when assessing elderly population. However, there is a paucity of sensitive and specific measures of cognitive assessment in India, especially for dementia.[4] NNB-E has been developed and standardized for Indian older adults.[7] It is a brief, simple, and culturally appropriate tool for Indian older adults. NNB-E is a comprehensive battery that taps the following domains of cognition: Attention, memory, executive functions, language, visuospatial construction, and parietal focal signs. The main purpose of the present study was to examine the validity of the NNB-E battery.

The comparison of normal controls and AD groups indicated that normal controls consistently scored higher on neuropsychological tests [Table 2]. This indicates that neuropsychological battery (NNB-E) can differentiate between the normal and clinical groups. Test of episodic memory (Word List-DR) was found to be particularly sensitive and showed highest discriminability. This was followed by Fluency (animals) and Story Recall Test. The results of the present study are consistent with those of other studies indicating that measures of episodic memory were considerably more effective for detecting early AD than the measures of non-memory domains such as semantic fluency, executive functions, or construction.[121314] The memory impairment implicates the temporal lobes and associated structures including hippocampus and entorhinal cortices, which are often the site of extensive degeneration in AD.[151617] Based on the finding from the current study, it is tempting to say that impaired episodic and semantic memory are potential cognitive markers in AD.

The second aim of the study was to examine the concurrent validity of the subtest of NNB-E. Results showed that all the subtests of NNB-E positively correlated with the scores on HMSE. This suggests that better performance on NNB-E is related to better performance on HMSE. Further, it was noted that CDR and EASI scores were negatively correlated with NNB-E, suggesting that a decline in performance on the battery were associated with increasing severity of dementia and difficulty in activities of daily living.

The findings of the present study demonstrate that all the subtests of NNB-E, which is specifically developed for Indian elderly with the use of material familiar to Indian population, can discriminate between healthy normal elderly from individuals with AD. It was also found that there is a positive association between NNB-E and HMSE and negative association with dementia rating scales. Therefore, theNNB-E has the potential to be a useful tool to assess cognitive functions in the Indian elderly.