Contextual risk factors for the common mental disorders in Britain: a multilevel investigation of the effects of place.

STUDY OBJECTIVE: To test hypotheses about associations between area level exposures and the prevalence of the most common mental disorders (CMD) in Britain. A statistically significant urban-rural gradient was predicted, but not a socioeconomic gradient, in the prevalence of CMD after adjusting for characteristics of individual respondents. The study tested the hypothesis that the effects of area level exposures would be greatest among those not in paid employment. DESIGN: Cross sectional survey, analysed using multilevel logistic and linear regression. CMD were assessed using the General Health Questionnaire (GHQ). Electoral wards were characterised using the Carstairs index, the Office of National Statistics (ONS) Classification of Wards, and population density. SETTING: England, Wales, and Scotland. PARTICIPANTS: Nearly 9000 adults aged 16-74 living in 4904 private households, nested in 642 electoral wards. MAIN RESULTS: Little evidence was found of statistically significant variance in the prevalence of CMD between wards, which ranged from 18.8% to 29.5% (variance 0.035, SE 0.026) (p=0.11). Associations between CMD and characteristics of wards, such as the Carstairs index, only reached statistical significance among those who were economically inactive (adjusted odds ratio for top v bottom Carstairs score quintile 1.58, 95% CI 1.08 to 2.31) (p<0.05). CONCLUSIONS: There may be multiple pathways linking socioeconomic inequalities and ill health. The effects of place of residence on mental health are greatest among those who are economically inactive and hence more likely to spend the time at home.

Predicting small-area health-related behaviour: a comparison of smoking and drinking indicators.

Health-related behaviours are of central importance to health promotion and to the promotion of enhanced population health. In the UK, localised knowledge of the quantitative dimensions of health-related behaviours is traditionally attained by conducting a costly sample survey. Such surveys seldom generate reliable data at scales more local than that of the health authority, they also need to be repeated regularly. This paper outlines an alternative framework for generating statistics on small-area health related behaviours using routinely available data from the annual Health Survey for England (N = 17,000) and the decennial Population Census. Using a multilevel modelling approach nesting individuals within postcode sectors within health authorities, and focusing on the prevalence of smoking and 'problem' drinking, the paper comprises four sections: a consideration of the modelling strategy, a comparison of the smoking and drinking models, an outline of the estimation strategy, and the presentation and discussion of ward-level estimates of smoking and drinking behaviour for England. The paper concludes that the method is better at estimating smoking than drinking but that it offers a feasible, cheap and more informative alternative to the survey approach to the generation of information on smoking and drinking behaviour.

Consumed with worry: 'unsafe' alcohol consumption and self-reported problem drinking in England.

Using data from the 1994 Health Survey for England, logistic multivariate multilevel modelling techniques are used to investigate the simultaneous effect of individual demographic characteristics and socio-structural factors on self-reported problem drinking as revealed by CAGE scores and 'unsafe' levels of alcohol consumption. Whilst the influence of key socio-structural variables is broadly similar for both unsafe alcohol consumption and high CAGE scores, there are notable exceptions when results are examined by tenure group: those in the rented sector are more likely to be problem drinkers as revealed by CAGE, but less likely to consume 'unsafe' amounts of alcohol. Both dimensions of drinking behaviour are influenced by the consumption patterns of others in the household, with both likelihoods increasing as the average consumption of others in the household rises. After taking into account individual compositional variables, the research indicates that there is very little evidence for geographical variation remaining in these two dimensions of drinking behaviour. It is found that the proportion of the population whose drinking behaviour may be classed as (potentially) problematic via the CAGE responses is substantially less than the proportion consuming above recommended 'safe' levels. The research concludes, however, that the two measures are broadly similar in their relationship to social and structural variables. Tenure provides an exception to this conclusion and indicates a continuing need to take account of housing circumstances in developing an understanding of drinking behaviour.

Factors influencing the fecal egg and oocyst counts of parasites of wild European rabbits Oryctolagus cuniculus (L.) in Southern Western Australia.

Abundance of intestinal parasites was monitored by fecal egg and oocyst counts for samples of wild rabbits Oryctolagus cuniculus with different levels of imposed female sterility from 12 populations in southwestern Australia. Differences in egg counts of Trichostrongylus retortaeformis between seasons and age groups were dependent on the sex of the host. Pregnancy may have been responsible for these differences because egg counts were consistently higher in intact females than in females surgically sterilized by tubal ligation. Egg counts for Passalurus ambiguus were influenced by season and host age but there were no differences between sexes or between intact and sterilized female rabbits. No differences were detected in the oocyst counts of the 8 species of Eimeria between male and female rabbits or between intact and sterilized females. Seasonal differences were detected in oocyst counts of Eimeria flavescens and Eimeria stiedai. The overwhelming determinant of coccidian oocyst counts was host age, with 6 species being much more abundant in rabbits up to 4 mo of age. There was a suggestion that egg counts of T. retortaeformis and oocyst counts of several species of Eimeria were reduced in populations where rabbit numbers had been depressed for at least 2 yr, but there was no evidence that short-term variations in rabbit numbers had a measurable effect on parasite abundance.

Evaluation of the association of parasitism with mortality of wild European rabbits Oryctolagus cuniculus (L.) in southwestern Australia.

Abundances of the parasitic nematodes Trichostrongylus retortaeformis and Passalurus ambiguus, and 8 Eimeria species were estimated by fecal egg and oocyst output in 12 discrete free-ranging populations of wild rabbits (Oryctolagus cuniculus) in southwestern Australia. Comparisons of parasite egg and oocyst counts were made between those rabbits known to have survived at least 2 mo after fecal samples were collected and those rabbits that did not survive. There were significant negative relationships between parasite egg and oocyst counts and survival when all age groups and collection periods were pooled for several species of coccidia and for T. retortaeformis. However, when the same comparisons were made within rabbit age groups and within collection periods, there were very few significant differences even where sample sizes were quite large. The differences indicated by the pooled analysis for coccidia were most likely due to an uneven host age distribution with respect to survival, combined with an uneven distribution of the oocyst counts with rabbit age. The result for T. retortaeformis was similarly affected but by a seasonal pattern. Parasitism by nematodes and coccidia did not appear to be an important mortality factor in these rabbit populations, at least at the range of host densities we examined. This suggests that other factors must have been responsible for the observed pattern of density-dependent regulation in these rabbits.

Choosing a national survey to investigate smoking behaviour: making comparisons between the General Household Survey, the British Household Panel Survey and the Health Survey for England.

BACKGROUND: Smoking behaviour is of central concern to enhanced population health and there is a recognized need for detailed information concerning many different aspects of this behaviour. This paper assesses the utility of three large-scale national surveys according to their ability to provide such information. These are the General Household Survey (GHS), the British Household Panel Survey (BHPS) and the Health Survey for England (HSE). METHODS: A number of important data items are identified and a comparative content analysis of the surveys is undertaken to indicate whether these items are present or absent in each source. RESULTS: Although current smoking status and consumption are covered in all three data sets, the GHS and the HSE provide information on many other aspects of the behaviour. Information on the major contextual variables can be found in each of the surveys. All sources can be used within a repeated cross-sectional analytical framework, and limited population-based longitudinal analyses can be undertaken with the GHS and the HSE. The BHPS theoretically opens up potential for a true longitudinal analysis of the cohort dynamics of individual smoking behaviour. Issues of place are best explored using the HSE, where the geographical information is most detailed. CONCLUSIONS: The paper highlights the importance of all three data sets as statistical modelling resources for investigating patterns of smoking prevalence. Although the advantages of the panel approach are noted for cohort-based longitudinal studies, there still remain some problems in undertaking these analyses because of the small number of BHPS waves carried out to date.

Fertility control of overabundant species; Can it work for feral rabbits?

Demographic changes were monitored in free-ranging European rabbit (Oryctolagus cuniculus) populations in Australia following the surgical imposition of four levels of female sterility (0%, 40%, 60%, 80%). Rabbit productivity decreased with increasing sterility level, but a greater proportion of offspring were recruited into populations with high levels of sterility. Adult rabbits, particularly sterile females, also survived better in the high sterility populations. Thus we were able to experimentally demonstrate that two density-dependent processes were operating on our rabbit populations: one was acting on juvenile survival, the other on the survival of infertile adult rabbits. However, these compensatory mechanisms were insufficient to overcome the effects of sterility in the high sterility populations and the seasonal abundance of rabbits decreased. Female sterility levels of 60%-80% would benefit rabbit control programs by reducing the peaks of rabbit abundance. This effect is likely to be enhanced if fertility control could be integrated with other pest control strategies.

Microsporidia (Encephalitozoon cuniculi) in wild rabbits in Australia.

OBJECTIVE: To determine the prevalence of infection with Encephalitozoon cuniculi in wild rabbit populations in Western Australia, and to isolate the organism from seropositive rabbits. DESIGN: Serological screening of wild and clinically affected domestic rabbit populations. SAMPLE POPULATION: Eighty-one wild rabbits from south-western Western Australia and 29 laboratory rabbits. PROCEDURE: Indirect immunofluorescence antibody technique and in-vitro amplification of parasite isolates in fibroblast cultures. RESULTS: Of the 81 wild rabbits and 29 laboratory rabbits, 20 and 22 respectively, had antibodies to E cuniculi. E cuniculi from the urine of one seropositive laboratory rabbit and from brain and kidney tissues of eight and five seropositive laboratory and wild rabbits respectively were isolated in fibroblast cultures. CONCLUSION: E cuniculi infection has been shown for the first time to be prevalent in wild rabbits in Australia. Techniques have been developed for the isolation and culture of the causative agent. Comparative studies can now be undertaken to determine risk factors for clinical disease in domestic rabbits and the relationship among E cuniculi isolates from wild and domestic rabbits.

Fluoroacetate content of some species of the toxic Australian plant genus, Gastrolobium, and its environmental persistence.

Gas chromatography confirmed the relatively high concentrations of fluoroacetate found in toxic Gastrolobiums, a genus of indigenous Australian plants. Fluoroacetate concentration in these plants ranged from 0.1 to 3875 micrograms/g (ppm) dry weight, with young leaves and flowers containing the highest concentrations. However, there was considerable intrastand variation between individual plants of at least two species with coefficients of variation ranging from 94% to 129%. Despite the high concentrations of fluoroacetate in many species, only one of nine soil samples collected from beneath these plants contained fluoroacetate. None of the 16 water samples collected from nearby streams and catchment dams contained fluoroacetate. This suggests that fluoroacetate does not persist in this environment. Fluoroacetate was also found in the genus Nemcia, and very low levels of fluoroacetate (ng/g) were detected in the foodstuffs, tea and guar gum. The latter indicates that other plant species may produce biologically insignificant amounts of fluoroacetate.

Physical versus chemical defence mechanisms in toxic Gastrolobium.

The degree to which physical defence mechanisms are present in toxic species of Gastrolobium was compared with the known fluoroacetate (the toxic principle) concentrations of these plants using both histological leaf sections prepared from fresh leaves (4 species), and a variety of visual external traits measured from herbarium specimens (28 species). There was a strong negative correlation between the presence of physical deterrents (e.g. area of fibres, number and length of spines) and the fluoroacetate concentration of each species. This suggests that, with respect to their leaves, individual species have established a compromise between producing physical grazing deterrents and the adoption of chemically mediated antiherbivore strategies.

The effect of sub-lethal doses of bromadiolone on the breeding performance of house mice (Mus domesticus).

Both laboratory and field strains of Mus were exposed to wheat containing 0.0001% bromadiolone under laboratory and outdoor conditions, respectively. While both strains readily consumed the poisoned wheat, ad libitum sub-lethal doses of this anticoagulant equating to between 20% and 70% of the acute LD50 per feed had little apparent effect on the breeding performance of these mice. The implications of these findings are discussed with respect to the use of anticoagulants as pesticides.

Health based geographical information systems: their potential examined in the light of existing data sources.

There is much potential for the use of geographical information systems (GIS) within the management and analysis of health and health care data. This paper addresses the problems of using routine data in the creation of geographical information systems for health. The numerous sources of British official routine health information however vary greatly in their geographical coverage and geographical detail. Particular attention therefore focuses upon the extent to which existing data sets can readily be used within GIS. Recommendations for changes in the data collection process are forwarded to improve the potential for GIS use. The overall utility of geographical health information systems within health service planning is illustrated using the example of community based activities.

Health education and baseline data: issues and strategies in nutrition campaigning.

A central problem for health education is the lack of baseline data concerning relevant issues such as smoking, alcohol consumption or nutrition. In the absence of this information there is little detailed knowledge of the public's habits or willingness to change those habits. Furthermore, the social context and spatial variation of these factors is unknown. Often the only way in which suitable information can be acquired is through social surveys. This paper uses a case study of a nutrition survey to outline a general framework for the collection of baseline data. The approach centres around postcode based data linkage. The effectiveness of the approach is considered and its shortcomings noted.

Metabolism of fluoroacetate in the skink (Tiliqua rugosa) and the rat (Rattus norvegicus).

Administration of 100 mg sodium fluoroacetate (compound 1080) per kilogram body weight to T. rugosa resulted in a 3.4-fold increase in plasma citrate levels 48 h after dosing while administration of 3 mg sodium fluoroacetate per kilogram body weight to R. norvegicus produced a fivefold increase in plasma citrate levels within 4 h. Administration of 300 mg sodium fluoroacetate per kilogram body weight reduced the oxygen consumption of the skink by between 2.5 and 11% while in the rat, 2 mg sodium fluoroacetate per kilogram body weight reduced oxygen consumption by between 28 and 57%. Aconitate hydratase activity in extracts of liver acetone powders from T. rugosa was less inhibited by (-)erythrofluorocitrate (Ki: 0.065 mM) than that in extracts derived from R. norvegicus (Ki: 0.026 mM). The rate of defluorination of fluoroacetate in erythrocytes and in extracts of liver acetone powders of T. rugosa was 8- and 4.5-fold greater, respectively, than that found in similar preparations from R. norvegicus. A rapid rate of defluorination together with a low reliance on aerobic respiration favoured detoxification of fluoroacetate in T. rugosa rather than its conversion into fluorocitrate. Though defluorination in this species helped to minimize the immediate effects of fluoroacetate on aerobic respiration, it resulted in rapid depletion of liver glutathione levels.

Significance of sulfhydryl compounds in the manifestation of fluoroacetate toxicity to the rat, brush-tailed possum, woylie and western grey kangaroo.

Levels of citrate in kidneys and livers of rats with normal glutathione levels increased 6.8 and 1.7-fold respectively 2 h after dosing with 1.5 mg of compound 1080 (= 95% sodium fluoroacetate) per kilogram body weight. In animals with liver glutathione levels 15% of normal, increases in plasma and liver citrate levels after dosing with fluoroacetate were significantly greater than those of control animals. Cysteamine and N-acetylcysteine, like glutathione, partially protected aconitate hydratase from fluorocitrate inhibition in rat liver preparations but were unable to replace glutathione as a substrate for the defluorination of fluoroacetate in vitro. N-Acetylcysteine did not diminish plasma citrate levels of glutathione-deficient rats dosed with fluoroacetate, while cysteamine inhibited the rate of in vivo defluorination in glutathione-deficient brush-tailed possums. It is suggested that non-physiological sulfhydryl compounds are ineffective antidotes to fluoroacetate intoxication in vivo. The in vivo defluorination patterns of four mammal species with differing sensitivities to fluoroacetate did not indicate a direct relationship between tolerance and rate of defluorination and it is also suggested that a high level of activity of the glutathione-S-transferase responsible for the defluorination of fluoroacetate is not the major mechanism for circumventing fluoroacetate toxicity in resistant mammals.