Two studies into a community catchment area population of schizophrenia patients find memory weakness .

a study published in the British Journal of Psychiatry 2000 [ memory schiz kelly ]

Cognitive function in a catchment-area-based population of patients with schizophrenia

C KELLY et al: Academic Department, Gartnavel Royal Hospital, Glasgow, Scotland.

All patients with schizophrenia in a catchment area were identified (n=182).

Measures of assessment were: National Adult Reading Test (NART),

Mini-Mental State Examination (MMSE),

go to ( see below ) Rivermead Behavioural Memory Test (RBMT),

Executive Interview (EXIT),

FAS Verbal Fluency and

Health of the Nation Outcome Scales (HoNOS).

 

Results We assessed 138 patients, mean age 48 years (standard deviation (s.d.) 15). Only 14% were in-patients. The mean premorbid IQ as assessed by NART was 98 (s.d. 14);

15% of patients had significant global cognitive impairment (MMSE);

81% had impaired memory (RBMT see below );

25% had executive dyscontrol (EXIT);

and 49% had impaired verbal fluency (FAS).

Scores on the functional impairment sub-scale of HoNOS correlated with all measures of cognitive impairment.

Conclusions Cognitive dysfunction is pervasive in a community-based population of patients with schizophrenia.

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Measuring memory impairment in community-based patients with schizophrenia

B J PSYCHIATRY 2006 189 132-136

a Case-control study

Correspondence: Dr Mohammed Al-Uzri, Neuropsychopharmacology Unit, Department of Health Sciences, Leicester General Hospital,
Leicester LE5 4PW, UK. Tel(0) 116 225 7924; fax: +44(0) 116 225 7925; email: mmaul@le.ac.uk

Department of Health Sciences, University of Leicester and Leicestershire Partnership NHS Trust
Al-Usri. J. Bruce, MBChB, MRCPsych, S. Frost, MBBS, MRCPsych and D. Mackintosh, MBChB, MRCPsych Leicestershire Partnership NHS Trust

We identified every patient with a possible diagnosis of schizophrenia, from psychiatric records, in one catchment area of approximately 100 000 people in south Leicestershire. This included examining old records of all psychiatric patients in the catchment area to make sure no potential patient was missed. The diagnoses were confirmed using ICD-10 criteria (World Health Organization, 1992). The area can be described as a suburban British residential area with a predominantly middle-class working population. The two consultants responsible for the area have a policy of not discharging patients with schizophrenia from their care even if the patients need minimal psychiatric input. The only exceptions were cases of severe and incapacitating schizophrenia that necessitated a referral to rehabilitation psychiatry. Such patients usually move out of the area into long-term care units or sheltered accommodation.

We excluded patients with organic brain disease, head injuries or comorbidity, and those whose first language was not English. None of the participants had had electroconvulsive therapy in the year prior to taking part in the study. Patients older than 60 years were also excluded, because Kelly et al (2000) suggested that people above this age with schizophrenia have a poorer cognitive performance than younger patients. The patients' performance on the memory test was compared with that of controls (n=71). Members of the control group live in the same city and were recruited by advertisements in the local hospital, university and supermarkets. They had no history of mental illness, and were subjected to the same exclusion criteria as the patient group.

Measures

Rivermead Behavioural Memory Test Participants were assessed with the Rivermead Behavioural Memory Test (RBMT; Wilson et al, 1985). This test of everyday memory has good ecological validity, and is made up of 12 measures, each aimed at testing one aspect of everyday memory:-

a. remembering a name;
b. remembering a hidden belonging;
c. remembering an appointment;
d. picture recognition;
e. immediate recall of a newspaper article;
f. delayed recall of a newspaper article;
g. face recognition;
h. remembering a new route (immediate);
i. remembering a new route (delayed);
j. delivering a message;
k. orientation questions;
l. knowing the date.

The RBMT has a screening score ( 0-12 simply pass or fail ), and is not very demanding in terms of effort or time (it takes 25-30 min to administer). It has been used before in schizophrenia studies, for example by McKenna et al (1990) and Kelly et al (2000)..... back to top

National Adult Reading Test
The National Adult Reading Test (NART; Nelson, 1982) is an estimate measure of premorbid intelligence. It has been widely used in psychiatric research and in particular in studies of schizophrenia (Gilvarry et al, 2001).

Positive and Negative Syndrome Scale

The Positive and Negative Syndrome Scale (PANSS; Kay et al, 1987) was given to patients only. It is a widely used scale for symptom ratings in schizophrenia. Health of the Nation Outcome Scales The Health of the Nation Outcome Scales (HoNOS; Wing et

 


 

We report a high prevalence of memory impairment (over 80%) in a population-based study of patients with schizophrenia.
This is based on the screening score of the RBMT, where a score of less than 10 is considered to represent impaired memory. This is, to the best of our knowledge, the second population-based study of cognitive impairment in schizophrenia after that by Kelly et al (2000). Significantly, we were able to replicate their findings regarding memory impairment using the same test, but in a demographically different population.

The patients who took part in our study were relatively young and free from psychotic symptoms, living in the community and with no documented comorbidity. The exclusion criteria were also designed to avoid the participation of any patients disadvantaged in terms of age and language. Except for years in education, there was no significant demographic or clinical difference between the patients who took part in the study and those who declined. This suggests that participants might have better memory functioning than those who declined to take part in the study.

Therefore, the prevalence of memory impairment reported would be a conservative estimate of its overall prevalence in schizophrenia when taking other confounding factors (clinical or demographic) into consideration. This is supported by the findings of Tamlyn et al (1992) who used the same test (RBMT) to examine their cohort; they reported a much higher prevalence of memory impairment in their subgroup of chronically ill and hospitalised patients, 27 out of 28 of whom scored in the impaired range.

The prevalence of schizophrenia in our study population (1.9 per 1000) is at the lower end of that expected (1.4-4.6 per 1000 population; Jablensky, 2000).
This could be explained by the demographic characteristics of the catchment area. As a suburban district, it is more likely to have a lower prevalence of psychotic disorders compared with city centres, which are associated with higher morbidity in general (Mortensen et al, 1999). In addition, patients who develop schizophrenia might well migrate towards the city centre, especially when they need supported or hostel accommodation, which is most likely to be available in urban areas.
This was particularly true for our study because patients who needed rehabilitation services and supported accommodation were moved outside the catchment area.


Our study suggests that the RBMT is a good clinical marker for memory impairment in schizophrenia. This is supported by previous use of the RBMT in studies of schizophrenia, which consistently showed that people with this disorder underperform on this test (McKenna et al, 1990; Kelly et al, 2000).
Our study had the advantage, compared with previous studies, of the inclusion of a control group. This made it possible to examine the ability of the RBMT in discriminating between patients and controls. It is not common in psychiatric research to have an instrument with such a good ability (76%) to predict patient or control status.
A similar ability (76%) was reported in previous work (Palmer et al, 1997); however, this involved a more demanding neuropsychological battery which is difficult to incorporate into everyday clinical practice, and furthermore lacked the specificity of everyday memory.

Therefore, the RBMT has the potential to become an important tool in our clinical practice for the identification of memory impairment in schizophrenia, which may help predict functional outcome.

Specificity of memory impairment

The premorbid IQ reported for the patients in this study was much higher than that reported in previous studies. This is another indication that our sample can be considered among the less ill of patients with schizophrenia, making the memory impairment reported even more significant. The difference in premorbid IQ between patients and controls was small in clinical terms, but statistically significant.

However, even after correcting for this difference in premorbid IQ, patients' performance on the RBMT was worse than that of controls.

Therefore, the underperformance of patients on the RBMT, as a measure of working memory, cannot be explained as a symptom of generalised reduction of intellectual ability, but is rather a specific cognitive deficit. Furthermore, this deficit was not related to symptom rating, except for negative symptoms, or medication in clinically stable patients. This supports the view that memory impairment is a core element of the clinical presentation of schizophrenia. The association between memory impairment and the negative symptoms sub-scale of the PANSS is an important replication of previous findings (Berman et al, 1997). Conceptually, both denote the lack of a normally existing function. More importantly, this is further evidence that they may have a common underlying substrate (Rossi et al, 1997). This is an important contribution of neuropsychology towards better understanding of the underlying pathophysiology of schizophrenia.

Memory impairment and level of functioning

The association of memory impairment with occupational group provides further evidence for the importance of such impairment in schizophrenia. This echoes previous findings (Green, 1996), which suggested an association between memory impairment and functional outcome.

This will have important implications for the development of any intervention that involves the use of memory.

First, it suggests that patients with such impairment might not benefit from interventions that require intact memory.

Second, it might be necessary to include memory remediation programmes in rehabilitation services to improve level of functioning.

Further validity for the RBMT comes from the significant correlation with the functional impairment sub-scale of the HoNOS. This finding echoes that previously reported by Kelly et al (2000), which reinforces the importance of memory impairment in influencing level of functioning in patients with mental illness.

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