Predicting memory performance in normal ageing using different measures of hippocampal size

A number of different methods have been employed to correct hippocampal volumes for individual variation in head size. Researchers have previously used qualitative visual inspection to gauge hippocampal atrophy. The purpose of this study was to determine the best measure(s) of hippocampal size for predicting memory functioning in 102 community-dwelling individuals over 80 years of age. Hippocampal size was estimated using magnetic resonance imaging (MRI) volumetry and qualitative visual assessment. Right and left hippocampal volumes were adjusted by three different estimates of head size: total intracranial volume (TICV), whole-brain volume including ventricles (WB+V) and a more refined measure of whole-brain volume with ventricles extracted (WB). We compared the relative efficacy of these three volumetric adjustment methods and visual ratings of hippocampal size in predicting memory performance using linear regression. All four measures of hippocampal size were significant predictors of memory performance. TICV-adjusted volumes performed most poorly in accounting for variance in memory scores. Hippocampal volumes adjusted by either measure of whole-brain volume performed equally well, although qualitative visual ratings of the hippocampus were at least as effective as the volumetric measures in predicting memory performance in community-dwelling individuals in the ninth or tenth decade of life.

Comparing white matter lesions on T2 and FLAIR MRI in the Sydney Older Persons Study

There is suggestion that magnetic resonance imaging (MRI) fluid-attenuated inversion recovery (FLAIR) sequence may be more accurate than T2 images in detecting white matter lesions (WML) in older people. Comparative ratings of these two image sequences have not been directly investigated in very old individuals to date. We compared the ratings of periventricular and deep WML on these two sequences in a sample of 111 community dwellers (mean age 85.5 years) using semiquantitative methods. Periventricular WML were as commonly detected on T2 as on FLAIR but were more severely rated on the latter sequence. No such bias was observed for the deep WML. With one exception, correlations between the two sets of measures were significant at the P < 0.001 level (range: 0.34-0.75). Intrarater reliability coefficients were moderate to excellent for most ratings. These results suggest that ratings performed on T2-weighted images to detect WML in very old individuals are very comparable with those performed on FLAIR images although FLAIR may allow a finer grading of periventricular lesions. Absence of FLAIR does not preclude the identification of WML in this population. These findings have clinical and epidemiological relevance where the acquisition of supplementary MRI data may not always be possible.

Gait slowing as a predictor of incident dementia: 6-year longitudinal data from the Sydney Older Persons Study

Current definitions for the preclinical phase of dementia focus predominantly on cognitive measures, with particular emphasis on memory and the prediction of Alzheimer's disease. Incorporation of non-cognitive, clinical markers into preclinical definitions may improve their predictive power. The Sydney Older Persons Study examined 6-year outcomes of 630 community-dwelling participants aged 75 or over at recruitment. At baseline, participants were defined as demented, cognitively intact or having a syndrome possibly representing the preclinical phase of Alzheimer's disease, vascular dementia, an extrapyramidal dementia or various combinations of the three. Those with cognitive impairment in combination with gait and motor slowing were the most likely to dement over the 6-year period (OR 5.6; 95% CI 2.5-12.6). This group was also the most likely to die (OR 3.3; 95% CI 1.6-6.9). White matter indices on MRI scanning were not consistently correlated with gait abnormalities. Simple measures of gait may provide useful clinical tools, assisting in the prediction of dementia. However, the underlying nature of these deficits is not yet known.

Hippocampal size and memory function in the ninth and tenth decades of life: the Sydney Older Persons Study

OBJECTIVES

The purpose of this study was to define magnetic resonance imaging (MRI) correlates of normal brain ageing, with the specific objective of investigating whether the size of the hippocampus is selectively correlated with age related memory performance in non-demented individuals in their ninth and tenth decades of life.

METHODS

Hippocampal size was estimated using MRI based volumetry and qualitative visual assessment in 102 community dwelling individuals aged between 81 and 94 years. Participants were evaluated on a variety of clinical and experimental instruments, including a comprehensive neuropsychological test battery. All participants underwent neurological examination, an extensive medical history was obtained, and an informant confirmed details of each participant's functional ability.

RESULTS

Both visual and volumetric hippocampal measures were identified as robust predictors of memory performance, even when the influence of age related illnesses and sociodemographic variables was accounted for. When the sample was reduced to include the most cognitively healthy participants who were rated by an informant as showing no evidence of cognitive decline, the left hippocampal measures remained significant predictors of delayed retention of verbal material.

CONCLUSIONS

These findings suggest that hippocampal volumes are selectively correlated with memory functioning in both normal and successful ageing.

Common factor models of validity and reliability for use with ordinal data in k x k tables

Three common factor models are proposed for the analysis of k x k ordinal data arising from test validity or reliability situations. These models represent an extension of the polychoric correlation model and item response theory. Identification is complete in the most usual reliability situation, where data from only two indicators (raters) are available. Full maximum likelihood estimation is available together with associated informative deviance tests and goodness-of-fit tests, examples of which are provided.

Preclinical syndromes predict dementia: the Sydney older persons study

OBJECTIVES

To identify if preclinical syndromes for Alzheimer's disease, vascular dementia, and Parkinson's disease and related dementias exist. Identification of dementia at early or even preclinical stages has important implications for treatment.

METHODS

A community dwelling sample of 647 subjects aged 75 and over at recruitment were followed up for a mean period of 3.19 years (range 2.61 to 4.51 years). Each subject was asked to participate in a medical assessment which included a standardised medical history examining both past and current health and medication usage; a neuropsychological battery (mini mental state examination, Reid memory test, verbal fluency, subsets of the Boston naming test and similarities, clock drawing and copied drawings) and physical examination. Preclinical syndromes for the three predominant dementias (Alzheimer's disease, vascular dementia and Parkinson's disease, and related dementias) and their combinations were defined using cognitive, motor, and vascular features. Their longitudinal outcome as defined by death and dementia incidence was examined.

RESULTS

Preclinical syndromes affected 55.7% (n=299) of subjects. Preclinical syndromes showed a trend for an increased odds of death (odds ratio 1.72, p=0.056) and a significantly increased odds of developing dementia (odds ratio 4.81, p<0.001). Preclinical syndromes were highly sensitive, detecting 52 of 58 (89.7%) incident dementias. Two hundred and sixteen of 268 (80.6%) preclinical subjects did not show dementia over the 3 year period (positive predictive value 19.4%). Subjects defined as having a combination of cognitive, extrapyramidal, and vascular features were at greatest risk of progressing to dementia.

CONCLUSIONS

Preclinical syndromes were sensitive and significant predictors of dementia. In view of their poor positive predictive value, the preclinical syndromes as defined in this study remain a research tool needing both definitional refinement and greater periods of observation. Multiple coexistent preclinical disorders resulted in a greater incidence of dementia, providing evidence for an additive role between multiple disorders.

The incidence of dementia in an Australian community population: the Sydney Older Persons Study

OBJECTIVES

Limited Australian dementia incidence data are available. This study aimed to identify the incidence of dementia and its subtypes in an Australian community dwelling population.

METHOD

A community dwelling sample of 647 subjects aged > or =75 years at recruitment were followed for a mean period of 3.2 years (range 2.6-4.5 years). The incidence of dementia (measured in person years at risk) was identified for different levels of severity of dementia, Alzheimer's disease and vascular dementia.

RESULTS

Incidence figures were slightly higher than those previously reported. The incidence of dementia and of Alzheimer's disease increased with age but was not affected by gender. The incidence of vascular dementia was not affected by age.

CONCLUSION

This study provides the largest body of data on the incidence of dementia in Australia, indicating a slightly higher incidence of dementia than previous reports. Further Australian data are required to confirm these findings.

Medical-care costs associated with posttraumatic stress disorder in Vietnam veterans

OBJECTIVE

This study examined the relationship between medical-care costs of Vietnam veterans and predictor factors, including posttraumatic stress disorder (PTSD).

METHOD

We merged medical-care cost data from the Department of Veterans' Affairs and the Health Insurance Commission with data from an epidemiological study of 641 Australian Vietnam veterans. Posttraumatic stress disorder and other factors were examined as predictors of medical-care cost using regression analysis.

RESULTS

We found that a diagnosis of PTSD was associated with medical costs 60% higher than average. Those costs appeared to be partly associated with higher treatment costs for physical conditions in those with PTSD and also related mental health comorbidities. Major predictors of medical-care cost were age ($137 per year for each 5-year increase in age) and number of diagnoses reported ($81 to $112 per year for each diagnosis). Mental health factors such as depression ($14 per year for each symptom reported) and anxiety ($27 per year for each symptom reported) were also important predictors.

CONCLUSIONS

The findings indicate that, however they are incurred, high healthcare and, presumably, also economic and personal costs are associated with PTSD. There is an important social obligation as well as substantial economic reasons to deal with these problems. From both perspectives, continued efforts to identify and implement effective prevention and treatment programs are warranted.

Anti-inflammatory drugs protect against Alzheimer disease at low doses

CONTEXT

Anti-inflammatory medications have an inverse association with Alzheimer disease (AD).

OBJECTIVES

To examine at what doses this anti-inflammatory drug effect occurs and whether other medications and/or International Classification of Diseases, Ninth Revision, Clinical Modification diagnoses affect the association.

DESIGN

Subjects 75 years and older from a random population sample were classified by consensus using International Classification of Diseases, Ninth Revision, Clinical Modification diagnoses. Drug associations with different types of dementia with and without the International Classification of Diseases, Ninth Revision, Clinical Modification diagnoses as well as dosage data were analyzed.

SETTING

The Centre for Education and Research on Aging, Concord Hospital, Concord, Australia.

PATIENTS

The Sydney Older Persons Study recruited 647 subjects (average age, 81 years). A total of 163 patients were given diagnoses placing them in different dementia categories and were compared with 373 control subjects. Of the patients with dementia, 78 had AD without vascular dementia, 45 had vascular dementia (permissive of other dementia diagnoses), and 40 had other dementia diagnoses (without AD or vascular dementia).

MAIN OUTCOME MEASURES

Fifty drugs or drug groups were subjected to a 2 (drug used vs drug not used) x 4 (dementia and control groups) chi(2) analysis. Drugs with inverse associations were identified and potential confounders (logistic regression) and dosage data (exact small sample 1-tailed tests) analyzed.

RESULTS

As expected, there was an inverse association between nonsteroidal anti-inflammatory drugs and aspirin (and unexpectedly angiotensin-converting enzyme inhibitors) and AD. This association was not observed with vascular dementia or any other diagnoses. Analysis showed no evidence for a dosage effect, ie, responses were equivalent for low and high doses.

CONCLUSIONS

This study does not support a high-dose anti-inflammatory action of nonsteroidal anti-inflammatory drugs or aspirin in AD. Potential mechanisms for the beneficial effects of these medications are discussed.

Motor function and disability in the dementias

Epidemiological and neuropathological series have identified three predominant dementing processes; Alzheimer's disease (AD), vascular dementia (VaD) and dementia associated with Lewy bodies (termed Parkinson's disease dementia (PDD) in this paper). While each has its own distinguishing features and by definition all impact upon day to day functioning, no random community derived sample has examined clinical features as defined by gait and balance abnormalities and compared disability ratings of the three dementias simultaneously. Six hundred and forty-seven community dwelling subjects participated in the Sydney Older Persons Study and of these 537 participated in a medical assessment. Of these 537,482 informants rated disability. Gait and balance abnormalities of the three major dementias were identified and the association of the dementias with disability examined. The three major dementias showed evidence of both slowing and ataxia in gait and balance tests. This was maximal in those with PDD. Similarly, all showed evidence of disability that was maximal in those with PDD. In conclusion, this study has identified that gait abnormalities are present in all three dementias to a varying degree. It is hypothesised that the varying levels of disability observed are a consequence of the varying levels of motor impairment, resulting in greater levels of disability in those with PDD.

Item bias in the Center for Epidemiologic Studies Depression Scale: effects of physical disorders and disability in an elderly community sample

The Center for Epidemiologic Studies Depression Scale (CES-D) is frequently used in studies of elderly individuals. One controversy regarding its use turns on the issue of whether the effect of physical disorder on the CES-D total score reflects genuine effects on depression or item-level artifacts. The present article addresses this issue using medical examination data from 506 community-dwelling individuals aged 75 or older. A form of structural equation modeling, the MIMIC model, is used, enabling the effect of a physical disorder on CES-D total score to be partitioned into bias and genuine depression components. The results show substantial physical disorder-related artifacts with the CES-D total score. Caution is required in the use of CES-D (and possibly other) depression scales in groups in which physical disorders are present, such as in elderly individuals.

Distress experienced by participants during an epidemiological survey of posttraumatic stress disorder

We examined the potential for epidemiological studies of mental disorders, specifically of posttraumatic stress disorder (PTSD), to cause further harm to participants involved. Of 1,000 randomly selected Australian Vietnam veterans, 641 agreed to participate in an epidemiological survey. Participants were asked about distress experienced during the interview when traumatic events were raised. Significant distress attributed to the interview was reported by 75.3% of those with current PTSD, 56.5% of those with past PTSD, and 20.6% of those with no PTSD diagnosis. Distress did not affect participants' use of medical services following the interview nor did it affect their willingness to continue participating in the study. We concluded that research interviews about PTSD may cause short-term distress, but found no evidence of long-term harm.

Alcohol consumption in a community sample of older people

OBJECTIVE

To examine the prevalence and pattern of alcohol use among community-living elderly Australians.

METHODS

A survey was conducted of randomly selected non-institutionalised people aged 75 years and older living in the inner western suburbs of Sydney. Personal interviews by trained interviewers covered background demographic information and self-reported alcohol use.

RESULTS

72% of men and 54% of women drank alcohol. The median usual daily volume of ethanol consumed by drinkers was 10 grams for men and 1.3 grams for women. However 11% of male drinkers and 6% of female drinkers consumed at defined hazardous or harmful levels.

CONCLUSIONS AND IMPLICATIONS

Although a sizeable majority of these older people were either non-drinkers or very light drinkers, a small but important proportion drank in the hazardous to harmful range. Despite increasing evidence of the health benefits of alcohol consumption it remains important to be alert for potentially harmful alcohol use among older people.

Effect of anti-inflammatory medications on neuropathological findings in Alzheimer disease

BACKGROUND

There has been no analysis of brain tissue from longitudinally observed, cognitively tested patients to validate whether anti-inflammatory medications protect against the pathological changes of Alzheimer disease.

OBJECTIVE

To investigate the role of anti-inflammatory medications in alleviating the pathological features of Alzheimer disease.

DESIGN AND MAIN OUTCOME MEASURES

A 5-year postmortem tissue collection was performed after a case-control study of Alzheimer disease (approximately 90 [30%] of patients died during follow-up, of whom consent for autopsy was obtained in 44 [50%]). Cases were selected on the basis of (1) adequate clinical histories of nonsteroidal anti-inflammatory drug usage, (2) no neuropathological findings other than Alzheimer disease, and (3) no generalized sepsis at death. Variables analyzed included neuropsychological test scores and amount of tissue inflammation and Alzheimer-type pathological changes. Two-way analysis of variance was used to determine whether drug usage significantly affected these variables.

SETTING

The Centre for Education and Research on Ageing and the Prince of Wales Medical Research Institute, Sydney, Australia.

PATIENTS

Twelve patients with Alzheimer disease (5 taking anti-inflammatory drugs) and 10 nondemented controls (3 taking anti-inflammatory drugs) were selected (50% of available sample).

RESULTS

Of the patients with Alzheimer disease, anti-inflammatory drug users performed better on neuropsychological test scores than did nonusers. However, there were no significant differences in the amount of inflammatory glia, plaques, or tangles in either diagnostic group.

CONCLUSION

Long-term anti-inflammatory medications in patients with Alzheimer disease enhanced cognitive performance but did not alleviate the progression of the pathological changes. Arch Neurol. 2000.

Evidence for association of anaemia with vascular dementia

The present investigation aimed to examine associations of anaemia with dementia. Analysis of community-dwelling, elderly subjects characterized for different dementias failed to confirm a previously reported association of anaemia with Alzheimer's disease (AD) but revealed instead a significant association with vascular dementia (VAD). Nearly 45% of VAD subjects were anaemic, compared with 17% of controls. Close to one-third of all subjects with haemoglobin levels > 0.5 g/dl below reference anaemia levels had VAD. Co-existing VAD may explain previous links between AD and anaemia. The association was independent of age, dementia severity and a range of other factors including vitamin B 12 and folate levels. Anaemia can exacerbate focal cerebral ischaemia and could precipitate or amplify VAD symptoms in elderly subjects with vasculopathy.

Posttraumatic stress disorder and other predictors of health care consumption by Vietnam veterans

A total of 641 randomly selected Australian veterans of the Vietnam War were interviewed about their use of health care in the previous two weeks to determine what factors contributed to health care consumption. Seventy-three variables were examined by univariate linear regression and then grouped into seven categories relating to age, physical and mental health, predisposition to posttraumatic stress disorder (PTSD), deployment and repatriation experiences, and membership in veterans groups. PTSD was associated with an additional cost of $79 in health care for the two-week period. Each physical diagnosis was associated with an additional $28. Alcohol consumption was not related to health care costs. Other important variables contributing to costs were depression, educational status, the quality of the repatriation experience, and social support.

Health habits and risk of cognitive impairment and dementia in old age: a prospective study on the effects of exercise, smoking and alcohol consumption

Previous research has yielded inconsistent results on the effects of exercise, smoking and alcohol use on cognitive impairment and dementia in old age. We analysed data from the Sydney Older Persons Study to see if these health habits were associated with cognitive functioning, dementia or Alzheimer's disease. Health habits were assessed in Wave 1 of the study, when the subjects were aged 75 years or over. Three years later, the subjects were tested for cognitive functioning and clinically examined for dementia and Alzheimer's disease. The analysis was restricted to the 327 subjects examined in Wave 2 who were non-demented in Wave 1. There were few significant associations between health habits and cognitive performance and these were not found consistently across cognitive measures. No associations were found with dementia or Alzheimer's disease. While these health habits do not affect risk for dementia and cognitive impairment in the very elderly, who are at highest risk for these disorders, we cannot discount a role at younger ages.

Postwar experiences and treatment-seeking behavior in a community counselling setting

Previous research investigating the impact of postwar experiences on Vietnam veterans has focused on veteran morbidity. This emphasis has meant that the impact of these factors on treatment-seeking behavior has received little empirical attention. This study examined the association between postwar factors and treatment-seeking behavior in a sample of 692 Australian Vietnam veterans. Logistic regression analyses were used to compute the odds ratios associated with postwar experiences and self-referral to a community-based counselling service. Results suggest that veterans who reported experiencing negative feelings toward others when they first arrived home were more likely to seek treatment. Other factors, such as a veteran's perception of societal attitudes and the reception they received, were not associated with treatment-seeking behavior.

Neurodegenerative and other chronic disorders among people aged 75 years and over in the community

OBJECTIVES

To assess age-related disease patterns in the older population in the community, especially the prevalence of neurodegenerative disorders and their association with systemic and vascular diseases.

DESIGN

Cross-sectional, community-based study.

SETTING

Area served by the Central Sydney Area Health Service, August 1991 to March 1994.

SUBJECTS

647 people aged 75 years or over, living in the community; 537 (83%) underwent medical assessment.

OUTCOME MEASURES

Clinician diagnoses of chronic disease, including neurodegenerative disorders (cognitive and visual impairment, gait ataxia and slowing, dementia and Parkinson's disease); arteriopathy score; age-related trends; and correlations among diagnoses and arteriopathy score.

RESULTS

Subjects had mean age of 81.0 years (range, 75-97). The most common diagnosis was arthritis (women, 73%; men, 68%), while the most common neurodegenerative diagnoses were gait ataxia (women, 57%; men, 42%), visual impairment (women, 40%; men, 45%) and cognitive impairment (women, 39%; men, 36%). Neurodegenerative diagnoses increased significantly in prevalence with increasing age, while most systemic diseases tended to decrease, although not significantly. Dementia was diagnosed in 92 subjects (17%), with Alzheimer's disease being the most common cause, but many having multiple causes. Significant correlations were found between neurodegenerative diagnoses and between the arteriopathy score and stroke, but not neurodegenerative diagnoses.

CONCLUSIONS

The increase in comorbidities in the older population arises from an age-related increase in neurodegenerative disorders. These form a cluster suggesting a common aetiologic process which is not arteriopathic.

Clinical diagnoses and disability of cognitively impaired older persons as predictors of stress in their carers

BACKGROUND

Aspects of the caring relationship are often promoted as more important than the clinical features of the care recipient in predicting caregiver wellbeing. However, studies of consequences of caring for cognitively impaired people seldom include detailed measures of the diagnostic profile and disability of the care recipient.

METHODS

Ninety community-living elderly persons with cognitive impairment were clinically assessed for severity on a range of illnesses. Their disability was examined via informant reports. Informants (88% of whom were primary carers) provided information on the behaviour and personality of the subject and reports of their own (informant) wellbeing. Using multiple regression, features of the subjects' clinical profile (severity of diseases, disability, behavioural problems and personality change) were examined as predictors of informant wellbeing. After controlling for subject clinical profile, we explored the additional associations between informant stress measures and other descriptors of the subject, caregiver and their relationship.

RESULTS

The subjects' clinical characteristics, in particular disability and disturbed behaviour, were strong predictors of caregiver wellbeing, accounting for most of the explained variance. After control for the subjects' clinical profile, few of the sociodemographic, caregiver or relationship variables examined had any influence on caregiver outcome measures. The exceptions were caregiver time demands, older subject age and self-identification as primary carer. Coresidence was not associated with caregiver distress.

CONCLUSION

Clinical characteristics of the care recipient are determinants of caregiver wellbeing, while socio-demographic, caregiver and relationship characteristics are less influential.

Help-seeking in Vietnam veterans: post-traumatic stress disorder and other predictors

This study investigated factors predicting help-seeking from the Department of Veterans' Affairs (DVA) by Vietnam veterans. Data used were from a national Australian survey of Vietnam veterans' health (n = 641) conducted between July 1990 and April 1993. The survey involved current clinical assessments and retrospective questionnaires, supplemented with health and service records retrieved from the DVA and Army personnel files. Measures included the 1989-90 Australian Bureau of Statistics Health Survey questionnaire, and mental health, sociodemographic and operational deployment history questionnaires. For both current and lifetime diagnoses of post-traumatic stress disorder, a third of the veterans with the disorder had never obtained any health care entitlement from the DVA. Other than physical and mental problems, which accounted for the greatest proportion of the help-seeking odds, significant factors predicting help-seeking included factors such as: predeployment personality, combat exposure, the veterans' own attitudes towards their deployment, experiences during deployment, experiences during repatriation and membership of ex-service organisations. These findings on how post-traumatic stress disorder and other health problems relate to help-seeking patterns could help in developing prevention and care programs for stress disorder.

Australian Vietnam veterans: factors contributing to psychosocial problems

OBJECTIVE

The objective of the present paper is to present comprehensive models of the current psychosocial morbidity of Australian Vietnam veterans. Seldom has research in this area attempted to 'untangle' direct and indirect influences on current functioning via possible pre-army, Vietnam and homecoming pathways.

METHOD

The Australian Vietnam Veterans' Health Study gathered data on a sample of 641 veterans throughout Australia drawn randomly from army Vietnam tour lists of the era. The data arose from interview and army records of the era, and fall into four temporal categories: pre-army, Vietnam service, homecoming after Vietnam, and current state. Path analysis models of the veterans' current psychological morbidities and social wellbeing are used to identify direct aetiological influences of earlier era constructs on current state, free of confounding by indirect (often selection) effects.

RESULTS

Our results indicate that psychological morbidity (particularly posttraumatic stress disorder) is largely influenced by combat and poor homecoming experiences, although pre-military characteristics do play some direct roles in symptomatology. Social dysfunction measures show smaller effects of the Vietnam War, which may be accounted for by an indirect association with Vietnam-related psychological morbidity. Some social measures show evidence of compensatory influences of combat, high combat leading to social dysfunction because of morbidity, but simultaneously being associated with healthier social disposition (possibly because of increased exservice activity).

CONCLUSIONS

For Australian Vietnam veterans, combat-related and homecoming effects persist on a range of psychosocial endpoints 20-30 years after exposure. These effects are not explicable in terms of veterans pre-Vietnam characteristics.

Interviewer effects on epidemiologic diagnoses of posttraumatic stress disorder

In an epidemiologic study of 641 interviewed subjects in the Australian Vietnam Veterans Health Study, three diagnoses of Vietnam combat-related posttraumatic stress disorder (PTSD) were obtained: lifetime prevalence using a variant of the Diagnostic Interview Schedule and lifetime and current (1-month) PTSD prevalence using the Standardized Clincical Interview for the Diagnostic and Statistical Manual of Mental Disorders, Third Revision. Prevalence estimates using the Standardized Clinical Interview varied according to interviewer characteristics (female vs. male, clinician vs. nonclinician) but not for the Diagnostic Interview Schedule. The authors use a simple variant of logistic regression to distill estimates of two informative parameters characterizing interviewers' judgments: severity threshold (related to the individual interviewer's criterion of "caseness") and reliability (related to degree of classification error of the individual interviewers). Examination of these estimates shows that female clinicians adopted lower severity thresholds for diagnosis of PTSD than other interviewers and hence had higher prevalence estimates while being relatively reliable in their judgments. Examination also shows that nonclinician interviewers can perform at least as reliably as clinicians. The Diagnostic Interview Schedule measure of PTSD was not moderated by these interviewer aspects. This use of threshold and reliability parameters is offered for routine use in epidemiologic field studies to examine potential interviewer effects.

Tetralin as a substrate for camphor (cytochrome P450) 5-monooxygenase

Camphor (cytochrome P450) 5-monooxygenase, originally isolated from the bacterium Pseudomonas putida PgG 786, catalyzes the essentially stereospecific conversion of tetralin (1,2,3,4-tetrahydronaphthalene) to (R)-1-tetralol ((R).(-)-1,2,3,4-tetrahydro-1-naphthol): tetralin(aq) + NADH(aq) + O2(aq) = (R)-1-tetralol(aq) + NAD(aq) + H2O(l). The ratio of the amount of (S)-1-tetralol to the amount of (R)-1-tetralol is small (approximately 0.04) and the reaction is essentially stereospecific. The reaction time-course plot indicates the formation of additional product(s) from the (R)-1-tetralol. It is found that the above reaction obeys Michaelis-Menten kinetics and that dimethyl sulfoxide, methanol, and p-dioxane serve as accelerators. Approximate values of a Michaelis constant Km, limiting rate Vmax, and catalytic constant kcat are obtained for this reaction under a specified set of conditions. It is shown by means of a thermochemical cycle calculation that the apparent equilibrium constant for this reaction is approximately 4 x 10(65) at T = 298.15 K and pH 7.3. Thus, this reaction is "irreversible" and, unless the enzyme system is inactivated, it will proceed in the direction of complete formation of 1-tetralol from tetralin. A detailed description of the preparation of the camphor (cytochrome P450) 5-monooxygenase enzyme system from recombinant microorganisms is given.

The Australian Vietnam Veterans Health Study: III. psychological health of Australian Vietnam veterans and its relationship to combat

BACKGROUND

Self-reported psychiatric status of Australian Vietnam war veterans was determined 20-25 years after the war and its relation to combat was investigated.

METHOD

A simple random sample of Australian Army Vietnam veterans was interviewed nationally using standardized interviews and self-completion tests to assess the prevalence of lifetime and current psychiatric illness and its relationship to combat. Army records were used to extract data on the cohort for use in regression-based adjustment for non-response.

RESULTS

The conditions mainly affecting the Australian veterans were alcohol abuse or dependence, post-traumatic stress disorder, somatization disorder were significantly related to combat exposure but not with posting to a combat unit. Less than half of the current one-month diagnoses were related to combat, possibly because of low power conferred by the relative rarity of these conditions.

CONCLUSIONS

The results confirm a range of psychological problems in former warriors may linger 20 or more years from their war exposure and may be directly affected by exposure to war trauma.

The Australian Vietnam Veterans Health Study: II. self-reported health of veterans compared with the Australian population

BACKGROUND

Self-reported physical health status of Australian Vietnam veterans was determined 20-25 years after the war and its relation to combat was investigated.

METHOD

An epidemiological cohort study of a simple random sample of Army veterans posted to Vietnam between 1964 and 1972 was conducted with personal interviews using the Australian Bureau of Statistics Health Interview Survey questionnaire to compare veterans with the Australian population and a 21-item combat exposure index used to measure the relationship of combat to physical health.

RESULTS

Veterans reported greater health service usage and more recent health actions than population expectations. They also reported excess health problems in almost all recent illness disease categories except endocrine conditions and cardiovascular conditions; only 6 of 37 chronic disease groups were not elevated compared to the population. Adjustment for non-response changed estimates only slightly. Combat exposure was significantly related to reports of recent and chronic mental disorders, recent hernia and chronic ulcer, recent eczema and chronic rash, deafness, chronic infective and parasitic disease, chronic back disorders and symptoms, signs and ill-defined conditions.

CONCLUSION

Combat exposure may have significantly increased reports of only some health problems. A general position to complain as a result of psychological conditions due to combat is not consistent with the lack of relationship between combat and reports of physical conditions.

The Australian Vietnam Veterans Health Study: I. study design and response bias

BACKGROUND

The Australian Vietnam Veterans Health Study was set up to examine the post-war health of former soldiers 20 or more years after service and to examine the relation of combat exposure to physical and mental health.

METHOD

A prospective cohort study of a simple random sample of 1000 male Australian Army Vietnam veterans used information gathered from Army records, from personnel interview and questionnaires. Military records were used to examine response bias by determining the differences between 641 interviewed veterans, 50 known deceased veterans and 309 non-respondents (including 48 refusers and 213 non-traceable).

RESULTS

Differences were evident between respondents and non-respondents, with logistic regression modelling pointing to pre-enlistment employment, antisocial behaviour, intelligence and post-Vietnam AWOL (absent without leave) as the most important discriminants with non-respondents performing worse. Compared to respondents, deceased left school earlier, had higher rank in Vietnam and at discharge, had a higher overall number of charges but not a higher rate overall, and were less likely to have gone AWOL. Deceased also received more casualty reports than respondents and non-respondents, were better behaved during service, and were better emotionally adjusted than non-respondents. Respondents compared with the Australian population had equivalent or better current socioeconomic status.

CONCLUSION

There seems little bias due to non-response, but deceased tend to come from and older cohort than in the other two groups.

The matter of scale

The genetic (and environmental) picture that emerges from a behavior genetic analysis is acknowledged to be a function of the scale upon which the particular trait being analyzed is measured. Differing views exist about how such data should be interpreted. The aim of the present paper is to air such issues and to emphasize that the reporting of substantive results, e.g. in psychiatric studies, should make clear that results are scale dependent, as this qualification may not be apparent to a psychiatric readership.

Twins reared together: minimizing shared environmental effects

The assumption that genetic variance is primarily (if not all) additive is usually made in biometric-genetic analyses of data collected on twins raised together. It is known amongst those familiar with twin methods that this assumption may lead to overestimates of heritability and under-estimates of shared environmental variance (E2), although this limitation is not always made clear to genetically native readers of such applications. The concept of "emergenic" genetic mechanisms (a potentially extreme epistatic or nonadditive mechanism) discussed by Lykken (1982) raises the possibility that genetic variance may be substantially nonadditive in some applications. The aims of the present paper are to investigate the potential size of such nonadditivity and such misestimations and to provoke discussion on the empirical plausibility (or otherwise) of epistatic effects. For if substantially present, the results of conventional twin analyses are substantially biased.

Limitations on the use of scales in psychiatric research

This paper discusses some issues involved in the construction and interpretation of scales in psychiatric research. The issues covered include scale construction, measures of scale homogeneity, the logic of factor analysis and the interpretation of effects manifesting in scale-data, especially interaction effects. The aim of the paper is to "de-mystify" some of the psychometric techniques commonly available, and to emphasize that their appropriate use depends on both a firm understanding of the content area to which they are applied and a rudimentary knowledge of what the methods purport to do.

Statistical diagnosis and the influence of diagnostic error

The optimal class of rules for allocating subjects, on the basis of an observable symptom profile, to sick or well states is based on the likelihood-ratio scale. This scale is estimated from a training set where the symptoms and true disease status are simultaneously measured. In the important case where true disease status is unavailable and only a "noisy" diagnosis can be performed, it is shown that exactly the same optimal class of allocation rules is obtained. This is true under very general assumptions of diagnostic error. Special cases are examined, providing insight into the dynamics of such diagnostic error. In particular, the conditions under which sensitivity, specificity, and the overall correct classification rate are underestimates of the true quantities are investigated.

The relationship between symptoms and diagnoses of minor psychiatric disorder in general practice

In an earlier paper (Goldberg et al. 1987) 36 common symptoms of minor psychiatric disorder in general practice were analysed using the technique of latent trait analysis. From this analysis two dimensions of illness emerged, corresponding to anxiety and depression. In the present paper, this symptom-based representation of minor psychiatric illness is used as a framework for comparing four diagnostic systems: General Practitioner (GP) diagnoses, the ID-CATEGO diagnostic system, the DSM-III system and the Bedford College diagnostic system. This analysis clarifies the reasons for disagreement among systems of diagnostic criteria and examines the practical effects of alternative diagnostic algorithms.

Can categorical and dimensional views of psychiatric illness be distinguished?

Bimodality in a distribution of symptoms is often claimed to be convincing evidence that a disorder is categorical, a discrete disease entity, rather than the extreme on a continuous dimension. However, using concepts from contemporary psychometric theory it is shown that bimodality can arise from the dimensional viewpoint. In fact, contrary to the usual belief, bimodality would be expected to occur in many research contexts if the dimensional alternative were correct.

Confounding confounding

Miettinen and Cook (Am J Epidemiol 1981;114:593-603) postulate that confounding is a result of exposure-strata dependence in the joint source population, irrespective of the effective parameter used. Boivin and Wacholder (Am J Epidemiol 1985;121:152-8) postulate that confounding is dependent on the additive structure of the crude effect parameter. Both of these conflicting principles are at variance with the familiar definition in terms of parameter bias. It is argued that the change-in-parameter definition is the only fundamental definition.

Diagnoses of dementia and depression: a latent trait analysis of their performance

Four diagnostic systems for dementia and depression are compared on a community sample of 274 subjects. They are: DSM-III, Gurland's system, AGECAT and a clinician's ratings. These are compared, not in the usual terms of prevalence rates and cross-tabulations of diagnostic categories, but by examining the performance of each system in terms of hypothetical, continuously distributed traits underlying the symptoms of dementia and depression, as in the latent trait model described by Duncan-Jones et al. (1986). Each diagnosis is characterized by the level of severity (threshold) at which it operates, and its accuracy. Evidence is given to support a dimensional view of dementia.

Social support, dementia and depression among the elderly living in the Hobart community

In a community sample of the elderly (N = 274) in Hobart, Tasmania, cases of dementia and depression were ascertained by the Canberra Geriatric Mental State and the Mini Mental State Examination. Social relationships and support were examined by means of the Interview Schedule for Social Interaction. The elderly had fewer social relationships than younger adults, but were more content with what they did have. Elderly women had more affectional ties than elderly men. The presence of offspring in the same town increased the number of close ties and of social relationships, but was more important for men than for women. Persons with cognitive impairment or an established dementia reported that they had less social interaction than they would like. Depressed subjects reported having markedly less social interaction than the mentally healthy elderly, but did not complain that it was too little. This study provides a systematic description of the social environment of the elderly, both in mental health and in states of depression or impaired cognition.

The utility of latent trait models in psychiatric epidemiology

Latent trait modelling is a recent psychometric technique with great potential for the construction and refinement of psychiatric instruments. It provides a greater insight into the nature of measurement in psychiatry and the statistical machinery for improving it. This expository paper starts with a non-technical outline of the latent trait model, gives a detailed analysis of the 12-item General Health Questionnaire (GHQ) and examines points raised by the empirical analysis through computer stimulation. It is shown that the latent trait model can give a good representation of empirical data and uncover new aspects of a familiar instrument. It provides a precise methodology for evaluating the functioning of a questionnaire and for developing better short instruments. It highlights the need, and provides the means, to tailor instruments for different tasks, such as (a) screening, and (b) measuring over the whole range of the population. We examine scoring in the light of the model, and show that simple scoring is often adequate. While points for further methodological development are noted, it is argued that the method is already sufficiently developed for general application.

Latent trait analysis of the Eysenck Personality Questionnaire

This paper exhibits contemporary psychometric models of questionnaires with dichotomous items. Such as approach allows assessment of individual items in terms of precision of measurement in ways not previously available. This Latent Trait Model approach is used to analyse the responses of 3806 subjects to the Eysenck Personality Questionnaire (EPQ). Short forms, of 10 items length, are recommended; they are the best possible such short forms, in that they provide the most accurate possible measurement overall.

Dementia and depression among the elderly living in the Hobart community: the effect of the diagnostic criteria on the prevalence rates

A survey was made of 274 non-institutionalized persons aged 70 and over living in Hobart. The prevalence of dementia and of depression was measured by interviewing subjects using a modified version of the Geriatric Mental State Schedule (GMS) (Copeland et al. 1976) and the Mini Mental State Examination (MMSE) (Folstein et al. 1975). Rates of morbidity were derived from different diagnostic procedures. These were: diagnoses made by a psychiatrist (A.S.H.) directly from the interview schedules and audiotapes, and rated as mild, moderate or severe; the criteria laid down in DSM-III, converted into algorithms describing 3 degrees of severity; and the algorithms for pervasive dementia and depression proposed by Gurland et al. (1983), and from these authors' rational scales. In addition, the relation between scales for dementia and for depression and the diagnosed categories was examined. Some problems in applying these methods to aged persons in the community are discussed. It is concluded that more detailed specification of criteria is desirable if the comparative epidemiology of dementia and depression in old age is to advance.