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Cochrane Dementia and Cognitive Improvement Group

Resources for review authors

CDCIG has just launched its new comprehensive, open-access register of intervention RCTs or studies of diagnostic tests in dementia treatment, prevention and cognitive enhancement: ALOIS

ALOIS is free to use and we hope it will be a valuable resource for review authors and the wider community.


You can review CDCIG editorial workflow charts here.


Getting involved as a Review Author: If you have expertise in some aspect of healthcare, consider joining the relevant Cochrane Review Group. If there is not yet a group which covers your specialty, register your interest in being part of a new group. Being part of a Cochrane review group provides the support, resources and training to tackle a systematic review, and an international audience when your work is published in The Cochrane Library.


Training - face-to-face

Contact Cochrane Centres or Review Groups about local workshops and courses in review production. Some of these events are listed on the Cochrane workshops page.

Training - online

  • Open Learning Materials - learn the steps in convenient online modules which supplement the Cochrane Reviewers' Handbook in helping you gain skills and complete your review.

Training resources provided by other organizations:


Methods used in reviews

Search strategies

Access to specialised register by reviewers

Reviewers can now search the CDCIG's Specialized Register online at www.medicine.ox.ac.uk/alois. ALOIS was launched in July 2009 as a study-based regsiter which contains bibliographic and other information on controlled trials that have been completed, are ongoing or are planned in the areas of dementia (prevention and treatment) and cognitive improvement. The site acts as an online and open-access version of the group's ProCite based SR.

In addition to ALOIS, the CDCIG Specialized Register is part of the CENTRAL database (search the Cochrane Library with the expression "SR-Dementia") and is available to all reviewer authors with access to The Cochrane Library. While  the CENTRAL database is an invaluable source of references, ALOIS is more up-to-date and extensive (it contains, for example open label extensions to RCTs and reviews) and above all it is study-based which means that more focussed searches can be carried out. Searches for reviews which fall within the scope of our Register are done by the Trials Search Co-ordinator at the Editorial base; searches for reviews outside the scope of the Register are generally carried out by the authors themselves with assistance of the Trials Search Co-ordinator when required. 

Additional search strategies

Review authors are expected to search the citations in relevant reviews for additional trials. Citations in each trial report are being searched for additional trials at the editorial base as and when we obtain copies of trials.

Study selection

CDCIG recommends that selection of studies for inclusion in a review is done independently by at least two review authors. Differences in study selection between reviewers should be resolved by discussion until consensus can be reached, or by consulting a third party.

Where there are no randomized controlled trials or controlled trials, other types of study may be discussed (at length if required) in the Background and Discussion sections of the review, but these may not be taken into account as evidence of efficacy.

Assessment of methodological quality

Please refer to the handbook 'How to Conduct a Cochrane Systematic Review'.

Data collection

Please refer to the handbook 'How to Conduct a Cochrane Systematic Review' and then to the CDCIG editorial base for further assistance.


Expert statistical guidance and advice is available to all review authors from our editorial base.

Reporting of reviews

Authors should refer to the licensing environment and stage of development of the drug in the protocol.

The following details a selection of scales and tests commonly used in prevention and treatment trials:

Speed of processing 
1) Boxes test (Earles 1995) is a paper-and-pencil test to assess sensory-motor speed; it comprises 100 three-sided boxes with a requirement to draw lines to complete each box. The score represents the number of boxes completed correctly in 30 seconds. 
2) Digit Symbol Coding Task (Wechsler 1997) is a symbol substitution task measuring the ability of participants to complete 133 substitutions on a printed sheet. The score is the number of correct substitutions completed in 120 seconds. 
3) Symbol Search Task (Wechsler 1997) is a subtest of the Wechsler Adult Intelligence Scale III measuring perceptual speed. Two columns of symbols are presented and the participants required to scan the columns and indicate if a symbol of one column appears also in the other. Final score represents the number of symbols identified correctly in 60 seconds. 
4) Continuous Attention Test (CAT) (Kalra 1993; Bryant 1998). This test assesses attention, visuo-spatial memory, and response speed. A series of 240 geometric shapes with 40 repetitions build up from a random pattern of four light and five dark squares arranged in a 3 x 3 grid. The duration of each stimulation was 0.1 second, and the interval between successive stimuli was 2 to 4 seconds. The task was to touch the response box with a touching pen whenever two patterns were the same. The number of repetitions identified correctly (cat-c) and incorrect responses was scored (cat-i). The error index was measured by expressing the total number of false negative and false positive responses as a proportion of the total response speed. 
5) Four-Choice Reaction Time (FCRT) (Kalra 1993; Bryant 1998). This test assessed attention, reaction time, and visuomotor coordination. Four circles could be arranged in the shape of a square. The task was to place the touch pen on an equivalent series of circles arranged in a square below on the same screen. At random intervals one of the circles was illuminated and the correct response was to touch the equivalent circle on the lower part of the screen as fast as possible. Three measures of accuracy and reaction time needed to be obtained: response to random stimuli, to fixed stimuli and the transition between the two. The results were the correct (fc-c) and incorrect response (fc-i) and the mean reaction time of the correct (fc-rtc) and the incorrect reaction responses (fc-rti). 
6) Digit-Symbol substitution (DSS). This test assessed attention, associative memory, and reaction time. A series of 10 digits appeared on top of the screen with corresponding symbols. A digit and a symbol were then projected on to the screen and the task was to touch a yes or no button depending on whether the combination was correct or not. The task was to idenitfy as many combinations as possible in 90 seconds. The score was the total number of correct (dsyn-c) and incorrect responses (dsyn-i). The mean correct reaction time (dsyn-rtc) and incorrect reaction time (dsyn-irtc) were scored.

Working memory
1) Digit Span-Backwards (Wechsler 1997). This is the digit span test used in the intelligence and memory scales of the Wechsler batteries as a measure of immediate verbal recall. It involves a range of different mental activities including auditory attention and short-term retention. The test consists of two trials for each span length, each string consists of two to eight random number sequences that the examiner reads aloud at the rate of one number per second. The participants are required to repeat the number strings in reverse sequence. One point is awarded for each string recalled correctly; if neither list is repeated successfully, a score of zero is given and the test ended. 
2) Letter Number Sequencing (Wechsler 1997). Chains of numbers and letters, from two to eight with three trials in each chain, are read to participants who are required to repeat first the numbers in given order then the letters in alphabetical order. One point is given for each chain recalled correctly.

1) The Rey Auditory Verbal Learning Test (RAVLT) (Rey 1964) is an easily administered test lasting 10 to 15 minutes that allows comparison between retrieval efficacy and learning. It measures immediate memory span and both short and longer term retention of a 15-word list following interpolated activity. Scores range from 1 to 5. 
2) Symbol Recall: requires recall of symbol-digit pairs from the Digit Symbol Coding test after completing the task. 
3) Activity Recall tests ability to remember information that was not explicitly presented as part of a memory task. A recall memory task required the participants to rename the 13 tasks that they have been exposed to and one point was given for each name recalled correctly according to order. 
4) Word learning test (Van der Elst 2006 a): involves memorizing 15 commonly used monosyllabic words that are printed on cards and presented in a fixed sequence at 2 s intervals. The task is to recall the words immediately and 20 minutes after presentation of the cards. The score is the maximum and the total number of correctly repeated words in the immediate recall test and in the delayed recall test. 
5) Scanning Memory Sets (SMS) (Kalra 1993; Bryant 1998): three numbers appeared on a screen for one minute and then disappeared. Then a single digit appeared on the screen. The task was to touch a yes or no button to indicate whether or not the number had been in the set. The subsequent set contained four numbers and the final set contained five. The total number of correct (sms-c) and incorrect (sms-ic) and the mean reaction time to the correct (sms-rti) and incorrect (sms-rti) responses was the total score.

Executive function
Executive function is a higher order cognitive activity controlling other cognitive activities including planning strategies for performance and using feedback to adjust future planning (Lezak 1995). The following measures were used for its assessment:
1) Stroop Test (Dodrill 1978). Dodrill's format of the Stroop test consists of one sheet containing 176 colour word names ("red", "orange", "green" and "blue") printed in a random order and in randomly assorted colours. In phase one of the task the participants are required to read the printed word name. The requirement in phase two is to report the colours in which the words are printed. The score is evaluated as the total time for phase one and the difference in time between phases one and two. 
2) Self-Ordered Pointing Task (Spreen 1998). This task assesses planning and organizing abilities as it relies on self-initiated responses (Petrides 1982). It assesses capacity to initiate and execute a sequence of responses with constant monitoring of performance. The participant is required is to point to one item on each page of a sequence without repeating an item already indicated. The participants therefore need to memorize items previously selected and to develop a strategy for pointing to all items available. 
3) Uses of Common Objects (Getzels 1962) test requires participants to give as many uses as they can for objects that customarily have a single function associated with them. The scores are based on the number and originality of the uses suggested. 
4) The Trail Making Test (Reitan 1985) has two parts. In part A participants are presented with a sheet randomly printed with numbers 1 to 25. The requirement is to join the numbers in sequence by tracing. Scores are derived as the time in seconds taken to complete the task. Part B presents numbers from 1 to 13 and letters from A to L in random placement. The requirement is to join the number and letters in numerical and alphabetical order. Scores are calculated by the time taken in seconds to complete the task. 
5) Verbal Fluency Task (Benton 1989; Benton 1994) comprises two parts, initial letter fluency and excluded letter fluency. In the first part, participants are asked to generate as many words as possible beginning with an allocated letter. The score is calculated as the number of words generated correctly in two trials of 60 seconds each. The excluded letter fluency task is to generate as many words as possible that do not contain the specified letter. The score is the number of correct words produced in two trials of 60 seconds each. 
6) Verbal fluency test (Van der Elst 2006 b). This test involves naming as many animals as possible in one minute. It measures word fluency or the ability to draw on one's encyclopaedic memory in a strategic manner. 
7) Concept shifting test (Van der Elst 2006 b). A timed test with four subtests testing flexibility in switching between two psychological concepts. Each subtest contained 16 circles (15 mm diameter) arranged in a large circle (16 cm diameter). For the first subtest, crossing off the circles in numerical and alphabetical order was required. 
8) Letter digit substitution test (Van der Elst 2006 b). A test to assess the speed of visual information processing. Nine different letters were assigned a unique number (1 to 9) in a key at the top of the form. A random series of letters in cells were presented and participants were instructed to add the corresponding digit to the letters. The score is the number of correctly corresponding digits in 90 seconds.

Verbal abilities
1) Vocabulary (WAIS-III) (Earles 1995) evaluates an individual's ability to define the meanings of 15 words. The score is 0, 1, or 2 based on the accuracy, precision, and aptness of definition. Vocabulary scores peak at middle age and show a slow average decline in the sixth to seventh decades. 
2) Spot- the-Word Task (Baddeley 1988). Two printed sheets each containing 60 real word paired with non-words, the participant's task being to identify the real word in each pair. Scores are calculated as the number of words identified correctly minus the number of errors (to correct for guessing).

1) The Center for Epidemiological Studies Depression Scale (CESD) (Radloff 1977) is a short self-report test designed to assess depressive symptomatology in the general population. The components of the scale include depressive mood, feelings of guilt and worthlessness, feelings of helplessness and hopelessness, psychomotor retardation, loss of appetite and sleep disturbance. There is a 1 to 4 point scale for each of 20 items with higher scores indicating more symptoms of depressive mood. 
2) The Profile of Mood State Questionnaire (POMS) (McNair 1971) assesses six aspects of mood: tension-anxiety, depression-dejection, anger-hostility, vigour-activity, fatigue-inertia, and confusion-bewilderment. The score is on a five-point ranging from 1 (no symptoms) to 5 (extreme symptoms).

1) Global Deterioration Scale (Reisberg 1982). This scale consists of a description of seven stages of dementia from 1 being normal to 7 where all verbal ability is lost. This scale has been shown to have a significant relation with anatomical brain changes as visualized on computerized tomographic scans (CT). 
2) Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) (APA 1994). This schedule provides clinical criteria for the listed categories of dementia - Alzheimer's disease, vascular dementia and dementia due to multiple aetiologies. The criteria include memory impairment and at least one of: aphasia, apraxia, agnosia, and disturbance in executive functioning. The cognitive deficits are required to cause significant impairment in social and occupational functioning, and the deficits do not occur exclusively during delirium and are not accounted for by depression. 
3) Rosen scale (Rosen 1984). This scale distinguishes between Alzheimer's dementia and vascular dementia in patients with known histological diagnosis. Scores ranging from 0 to 2 for Alzheimer's disease and 4 to 10 for vascular dementia. Features of primary importance are: abrupt onset, stepwise deterioration, history of stroke, focal neurological signs, and focal neurological symptoms. A feature of secondary importance is a history of hypertension. 
4) The Mini Mental State Examination (Folstein 1975) is the most widely used test of cognitive function. It is a short performance test (5 to 15 minutes) and has been validated for screening for dementia with a sensitivity of 69% and a specificity of 90% (Feher 1992). The test evaluates cognition in five areas: orientation, immediate recall, attention and calculation, delayed recall and language. Scores range from 0 (severe impairment) to 30 (normal). Scores below 24 (25 for well-educated subjects) are suggestive of dementia (Galasko 1990). 
5) Randt Memory Test (RMT) (Randt 1983) is a memory test for longitudinal assessment of mild and/or moderate memory storage and retrieval functions. It takes approximately 20 minutes and comprises five different parallel forms of acquisition, recall, and memory subtests. Scores are adjusted for age. 
6) The Modified Telephone Interview for Cognitive Status (TICS-M) (Prince 1999) was developed to provide follow-up documentation on patients already examined in the clinic or research project. Validated as a sensitive and specific screening instrument for dementia, the test lasts less than 30 minutes and assesses orientation, concentration, immediate and delayed memory, naming, calculation, comprehension and reasoning. TICTS-m has several different versions, the version used in Clarke 2003 comprised 13 items with a maximum score of 39 points. It includes an effortful list-learning task with delayed recall. 
7) Cognitive section of the Alzheimer's disease Scale (ADAS-Cog) (Rosen 1984) comprises 11 individual tests, spoken language ability (0-5), comprehension of spoken language (0-5), recall of test instructions (O-5), word-finding (0-5), following instructions (0-5), naming objects (0-5), construction drawing (0-5), ideational praxis (0-5), orientation (0-8), word recall (0-10) and word recognition (0-2). The scores range from 0 to 70, a higher score indicating impairment. 
8) Digit Symbol Substitution Test (DSST) (Wecshler 1981). 
9) Prorated Verbal IQ. This is a measure of intellectual function. Items from the Information, Vocabulary, and Similarities subtests of the Wechsler Adult Intelligence Scale-revised was used Welchsler 1982. 
10) Boston Naming Test (Kaplan 1983). Object-naming test detected difficulties in confrontation naming. 
11) Controlled Oral Word Association Test (Benton 1955). A measure of verbal fluency. 
12) Logical Memory and Associated Learning subtests from the Wechsler Memory Scale. A measure of short-term verbal memory (Wechsler 1955).
13) Benton Visual Retention Test (Benton 1955). A measure of the visuospatial memory. 
14) Trail Making Test A and B (Reitan 1992). A measure of visual scanning, conceptual flexibility, and motor speed. 
15) Finger tapping Test (Reitan 1974). A measure of motor speed for both dominant and nondominant hands.

Activities of daily living and behaviour scales 
1) Bristol Activities of Daily Living Scale (Bucks 1996). This 20-item scale uses a five-point severity grading for basic activities of daily living such as feeding, eating, dressing, toileting and instrumental activities of daily living (more complex tasks such as shopping, travelling and handling finances). It is an easy test that can be used by carers. 
2) Social Behaviour (SB) subscale of the Nurses' Observation Scale for Geriatric patients (NOSGER) (Spiegel 1991). The NOSGER contains 30 items of behaviour, each rated a five-point scale according to frequency of occurrence. Item scores are summarized into six dimension scores (memory, instrumental activities of daily life, self-care, social behaviour, and disturbing behaviour).

Page last updated: Thu 10th Dec 2009 15:49:34 CET