Previous work on the association between total aluminum (Al) concentrations and a measure of cognitive impairment is extended by considering the associations between this measure of cognitive impairment, not only with total Al, but also with turbidity and DOC both of which also contain Al. The multivariate, but not bivariate, analyses show that the odds of showing indications of mental impairment increase with turbidity but decrease with DOC, and this effect is most pronounced at a medium pH. It is suggested that the two variables considered could account for some of the unexplained features of the association between Al concentrations and measures of cognitive impairment. The other associations, namely those with F, pH, source of drinking water (ground or surface) remain similar to those reported previously in this series of papers.

A census was taken on 26 long-term care facilities in the Ottawa-Carleton Region comprising 3, 825 residents to estimate the point prevalence of cognitive impairment or dementia. Nurses familiar with the residents identified those who had either memory impairment or dementia (according to DSM III criteria). A validation of the data obtained through the census was carried out on a stratified, random sample of residents. The long-term care facilities were stratified by level of care and by size. From each of the three strata, 11 facilities were randomly selected then a 10 per cent random sample with replacement (411 residents) was determined. The validation survey consisted of interviewing residents using two screening instruments, interviewing the nurse using two behavioural instruments and a chart audit. On the census the prevalence for cognitive impairment in the surveyed group was 67 per cent compared to 61 per cent for the whole resident population. The sensitivity and specificity for cognitive impairment was calculated at 84 and 70 per cent respectively. The prevalence of dementia in the surveyed group was 61 per cent compared to a census estimate of 52 per cent for the whole resident population. The overall sensitivity of the census for dementia was 95 per cent and the specificity was 83 per cent. The results indicated that a census undertaken with standardized definitions, by knowledgeable staff directly involved with patient care is a reasonably effective method for estimating the prevalence of persons with dementia in long-term care facilities.

Schizotypal personality disorder is the DSM equivalent of the ICD category schizotypal disorder. It may be seen as part of the schizophrenia spectrum of disorders. Patients with schizotypal personality disorder (SPD) share many features with schizophrenic patients. These include symptoms of social isolation and cognitive impairment. They also share imaging and biochemical evidence of brain dysfunction, and genetic similarities. SPD patients, however, for some reason do not become chronically psychotic. The study of schizotypal patients is of great importance in attempting to clarify the genetic and biological basis of the schizophrenia spectrum. It is also important in helping to delineate the differences between schizophrenic and schizotypal patients, and to distinguish those factors that protect the schizotypal patient from becoming floridly psychotic. In this article we present recent findings regarding the biological basis of schizotypal personality disorder. We illustrate the contribution of these findings to our understanding of risk and protective factors in the schizophrenia spectrum.