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Biomedical subjects

R M Anderson

Publications and source records attributed to R M Anderson.

At least 163 records · Page 9Linked to original sources
PubMed1994

Influence of a highly focused case on the effect of small-group facilitators' content expertise on students' learning and satisfaction.

BACKGROUND: There has been considerable debate over the need for content expertise to lead a successful small-group discussion for medical students. Some authors feel process expertise related to the conduct of a small group is of more value than content expertise related to the case. At least one study has presented data that suggest content expertise can lead to teacher domination of the learning environment. In an earlier study, the present authors found that students learned more and were more satisfied with small-group instruction when the instruction was facilitated by a faculty member who was an expert in the content of the case. That study also identified no tendency for content experts to dominate the sessions (e.g., through lecturing or otherwise controlling the learning environment). The purpose of the present study was to explore the efficacy of a carefully designed and highly focused case problem to remove the influence of group facilitators' content expertise on students' learning outcomes. METHOD: The 211 students in the University of Michigan Medical School class of 1994 were randomly assigned to 28 groups in a microbiology and immunology course in the fall of 1991; each small group was led by a faculty facilitator. Complete data were available from 27 groups: 13 groups led by experts and 14 groups led by non-experts. Data collection included observers' codings of interactions between the students and the facilitators (interactional analysis), test scores, and students' ratings of the experience. RESULTS: Unlike in the previous study, group leaders who were content experts devoted significantly more time to teacher-directed activities than did non-content-expert leaders. However, overall, 62% of the time was devoted to student-initiated activity. The results of the multiple-choice tests that were related specifically to the goals of the case indicated there was no significant difference between the students' performances in the groups led by experts and those led by non-experts. With respect to students' satisfaction, all students gave consistently high ratings to the experience and there was no difference between groups led by expert and non-expert facilitators. CONCLUSION: The data from this study suggest that a facilitator's content expertise alone does not determine the amount of teacher-directed behavior in a group, the amount of students' learning, or students' satisfaction. The focus built into the case and the amount of facilitator's training directly related to the content of the case are also significant variables related to students' learning, teacher's behavior, and students' satisfaction.

Curriculum↗
PubMed1994

Modeling the impact and cost-effectiveness of HIV prevention efforts.

OBJECTIVES: This study explores how mathematical models can be used to examine the relationship between the effectiveness and costs of different prevention strategies. The analysis, based on a model designed to simulate the spread of HIV in sub-Saharan Africa, illustrates how the impact and relative cost-effectiveness of a prevention programme are sensitive to a number of factors including the rate of spread of HIV prior to the introduction of the programme, the measure used to evaluate the impact of the programme, and the point when the programme is introduced in the epidemic. RESULTS: Assessing the impact and cost-effectiveness of different HIV prevention strategies is problematic. Not only are there difficulties in collecting the relevant data, but the impact of a prevention programme may be highly non-linear in character because of the many factors that determine the net rate of viral transmission. The long incubation period of HIV further complicates the analysis as the benefits from preventing a case of infection extend over a number of years. CONCLUSIONS: The results highlight the need to collect more data on the impact and costs of prevention programmes if we are to ensure that the available resources for HIV prevention are to be used both efficiently and equitably.

Africa South of the Sahara↗
PubMed1994

Sexual behaviour survey in a rural area of northwest Tanzania.

OBJECTIVE: Little is known about variations in patterns of sexual behaviour in different countries, cultures, and subpopulations that determine the spread of HIV-1. Quantitative studies are required to improve understanding. METHODS: To assess reported patterns of sexual behaviour, we administered a standardized questionnaire to 416 men and 498 women aged 15-49 years from a rural population in northwest Tanzania. RESULTS: Reported levels of sexual activity were highest in men and among younger age groups. The number of sexual partners and number of sex acts per unit of time were strongly correlated: men reported 10 times as many lifetime partners than women. Frequency of sexual partner exchange plateaued earlier in women (by age 25 years) than in men (by age 35 years). For the great majority, age of first intercourse was 15 years or younger; older subjects were older at first intercourse and had fewer lifetime partners than younger subjects. CONCLUSIONS: This age-related pattern suggests that more recent birth cohorts have behaviour patterns that increase the risk of sexually transmitted infectious agents such as HIV. Preventive education programmes should be targeted at young adults, who adopt higher risk profiles of frequent partner exchange linked with first intercourse at an early age.

Adolescent↗
PubMed1994

Community diabetes care. A 10-year perspective.

OBJECTIVE: To compare diabetes care and education at the community level in 1981 and 1991 in order to record progress achieved in the decade of the 1980s, determine if there is a gap that must be closed to reach diabetes-related objectives for 2000, and establish a baseline to which changes stimulated by the Diabetes Control and Complications Trial can be compared. RESEARCH DESIGN AND METHODS: In eight Michigan communities, representative primary-care physicians (61 in 1981; 68 in 1991) and their diabetic patients (428 and 440) were identified. Communities, physicians, and patients were randomly selected. Participating patients were interviewed and examined in their community or home to assess the kind and extent of diabetes care they had been receiving; their metabolic, nutritional, educational, and psychosocial status; their diabetic history and current status; and other related factors. The diabetic status, care, and education of the 1981 community patients were compared with those of patients studied in 1991. RESULTS: Positive changes in diabetes care and education at the community level from 1981 to 1991 were seen in the areas of patient glucose monitoring, insulin administration practices, hypertension control, exercise recommendations in diabetic management; and smoking rates. Negative changes occurred in the percentage of non-insulin-dependent diabetes mellitus (NIDDM) patients receiving diabetes education and frequency of office visits to the patient's primary-care physician. Changes of indeterminate value included a sharp decline in primary diabetes admissions to the hospital and a decrease in the proportion of NIDDM patients managed with insulin. Many other hoped-for changes from 1981 status, such as screening for retinopathy, foot-care practices, and overall metabolic control of diabetes, did not occur. CONCLUSIONS: The decade of the 1980s produced modest, but not impressive, improvements in diabetes care and education at the community level. Progress must be accelerated if the diabetes-related objectives included in the national targets for health promotion and disease prevention for 2000 are to be met.

Adult↗
PubMed1994

A device for cutting brain slices.

A device for cutting brain slices is described as an alternative to cutting angle guides and the "brain macrotome." With this new device, slices of uniform thickness optimal for assessing morphological detail and photography can be produced. A similar but smaller device for cutting pieces of tissue for paraffin embedding is also presented. These devices should be useful in either the histopathology laboratory or mortuary.

Autopsy↗
PubMed1994

Determinants of the demographic impact of HIV-1 in sub-Saharan Africa: the effect of a shorter mean adult incubation period on trends in orphanhood.

Recent evidence suggests that the adult HIV-1 incubation period may be shorter in some sub-Saharan African populations than in Western populations. In this article we use mathematical-model-based simulations to show that, other things being equal, a shorter incubation period can result in smaller but more pronounced HIV-1 epidemics and faster, more acute, changes in demographic features, such as adult mortality, orphanhood and population structure. Empirical studies of orphanhood reveal similar patterns to those found in the simulations, but suggest that migration patterns and structural factors can give rise to greater concentrations of orphans in areas of relatively low HIV-1 prevalence.

Adolescent↗
PubMed1994

Is HIV-1 likely to become a leading cause of adult mortality in sub-Saharan Africa?

Concerns are sometimes expressed at the extent to which HIV-1 is prioritized within international and national health budgets and as a research issue, on the grounds that much larger numbers of people in developing countries currently die from other diseases, such as malaria and tuberculosis. We use a previously described mathematical model to explore how the HIV-1 epidemic could develop within a sub-Saharan African context and investigate the trends and patterns of adult mortality which could follow. Two contrasting scenarios are studied, one which turns population growth rates negative and another which does not. In both cases, HIV-1-related disease accounts for over 75% of annual deaths among men and women aged 15-60 years by year 25 of the epidemic. Relatively little change in mortality is seen in the early years of the simulated epidemics. However, by year 15, expectation of life at age 15 has fallen from 50 to below 30 years. The fragmentary evidence now available from empirical studies supports the impression that HIV-1 is rapidly emerging as a leading cause of adult deaths in areas of sub-Saharan Africa. Observed patterns of age-dependent mortality reflect those projected in the model simulations.

Adolescent↗
PubMed1993

Pulse mass measles vaccination across age cohorts.

Although vaccines against measles have been routinely applied over a quarter of a century, measles is still persistent in Israel, with major epidemics roughly every 5 years. Recent serological analyses have shown that only 85% of Israelis aged 18 years have anti-measles IgG antibodies. Considering the high transmissibility of the virus and the high level of herd immunity required for disease eradication, the Israeli vaccination policy against measles is now being reevaluated. Motivated by theoretical studies of populations in perturbed environments, we examined the possibility of replacing the conventional cohort vaccination strategy by a pulse strategy--i.e., periodic vaccination of several age cohorts at the same time. Numerical studies of a deterministic age-structured model suggest that vaccination, which renders immunity to no more than 85% of the susceptible children aged 1-7 years, once every 5 years will suffice to prevent epidemics in Israel, where infection rate is highest amongst schoolchildren. The model suggests that by using such a strategy the density of susceptible individuals is always kept below the threshold above which recurrent epidemics will be maintained. Analysis of simpler, non-age-structured, models serves to clarify the basic properties of the proposed strategy. Our theoretical results indicate that the advantages and disadvantages of a pulse strategy should be seriously examined in Israel and in countries with similar patterns of measles virus transmission.

Adult↗
PubMed1993

Factors controlling the spread of HIV in heterosexual communities in developing countries: patterns of mixing between different age and sexual activity classes.

The paper describes the development and analysis of a mathematical model of the spread and demographic impact of HIV in heterosexual communities in developing countries. The model extends previous work in this area by the representation of patterns of mixing between and within different age and sexual activity classes in a two sex structure. Summary parameters are derived to represent different mixing patterns, ranging from assortative via random to disassortative, as are methods to ensure that particular mixing patterns between different age and sexual classes (stratified on the basis of rates of sexual partner change) meet constraints that balance the supply and demand for sexual partners as AIDS induced mortality influences the demographic structure of a population. Analyses of model behaviour rely on numerical methods due to the complexity of the mathematical framework, and sensitivity analyses are conducted to assess the significance of different assumptions and different parameter assignments. Simulated patterns of HIV spread across the two sexes and various age classes are compared with observed patterns in Uganda. The principle conclusion of the study is that the pattern of mixing between age and sexual activity classes, combined with the assumptions made to balance supply and demand between the sexes have a very major influence on the predicted pattern of HIV spread and the demographic impact of AIDS. The paper ends with a discussion of future needs in model development and data acquisition.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Immunological modulation and evasion by helminth parasites in human populations.

Helminth parasites are highly prevalent in human communities in developing countries. In an endemic area an infected individual may harbour parasitic worms for most of his or her life, and the ability of these infections to survive immunological attack has long been a puzzle. But new techniques are starting to expose the diverse mechanisms by which these agents modulate or evade their hosts' defences, creating a dynamic interaction between the human immune system and the parasite population.

Animals↗
PubMed1993

Measles immunization strategies for an epidemiologically heterogeneous population: the Israeli case study.

Although the vaccine against measles has been routinely applied over a quarter of a century, measles is still an active disease in Israel. The January 1991 outbreak caused high morbidity in infant and adolescent populations and high mortality, especially among nomad Bedouins in the southern region of the country. The Bedouins form a small fraction of the total Israeli population (ca. 2%), but it is thought that they may experience significantly higher rates of transmission than the majority group. In this work we use deterministic compartmental mathematical models to define the optimal immunization strategy for a population consisting of a majority group characterized by low transmission rates and a minority group characterized by high transmission rates; this study allows both for transmission differences between the two groups, and for possible differences in the average cost (or difficulty) in reaching individuals for vaccination. Our analysis shows that the optimal vaccination policy for such a population involves different strategies for the two groups: a smaller fraction is to be vaccinated in the minority group if transmission in this group is not much larger than in the majority group, whereas, if the difference in transmission is very large, a higher proportion is to be vaccinated in the minority group. The advantage of this non-uniform vaccination policy is that it involves vaccination of a smaller fraction of the total population (and costs less, if there are differential costs between the groups), as compared with the proportion vaccinated under the conventional uniform vaccination policy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1993

AIDS predictions.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1993

No reason for complacency about the potential demographic impact of AIDS in Africa.

Much uncertainty surrounds the likely demographic impact of AIDS in the worst afflicted regions of the developing world such as sub-Saharan Africa. Various research groups have published projections of future trends but these differ widely with respect to potential impact on net population growth rates. Pessimistic forecasts suggest that AIDS may reverse the sign of a 3% to 4% population growth rate before the establishment of HIV, over time periods of a few to many decades. Optimistic forecasts suggest a decline in population growth rates, but predict that a 3% growth rate before AIDS may be reduced by only about 50% over a period of a few decades. This paper reports new analyses of the demographic impact of AIDS, based on observed age-stratified prevalences of HIV-1 infection amongst women of child bearing age. It is assumed that the observed patterns reflect the final endemic state and the implications of this assumption for adult and infant mortality and female reproductive life expectancy are assessed. It is concluded that a variety of scenarios is possible, depending on the detail of assumptions concerning life expectancy before the arrival of AIDS, the incubation period of the disease, and the rate of vertical transmission. Realistic assumptions do suggest, however, that the observed prevalences of infection in the worst afflicted regions of sub-Saharan Africa are sufficient to reduce current population growth rates to close to, or below, zero in the coming decades.

Adolescent↗
PubMed1993

A comparison of the diabetes-related attitudes of health care professionals and patients.

The following study compares the diabetes-related attitudes of sampled health care professionals and patients with diabetes. Attitudes were measured with a revised version of the Diabetes Attitude Scale (DAS) which includes seven factors representing attitudes towards: (1) the need for special training in order to provide diabetes care; (2) patient compliance; (3) the seriousness of noninsulin-dependent diabetes (NIDDM); (4) the relationship between blood glucose levels and the complications of diabetes; (5) the impact of diabetes on the patient's life; (6) patient autonomy; and (7) team care. The highest levels of agreement among patients and professionals concerned the seriousness of NIDDM and the relationship between blood glucose control and the development of the complications of diabetes. The most striking finding of the study was that patients tended to express a significantly more judgmental, moralistic attitude toward patient behavior than did health care professionals.

Attitude of Health Personnel↗
PubMed1993

Dynamic interaction between Leishmania infection in mice and Th1-type CD4+ T-cells: complexity in outcome without a requirement for Th2-type responses.

The interaction between Leishmania parasites and Th1 cells is investigated using a simple mathematical model of immunological responses and parasite population growth within the host. The model generates patterns of resistance and susceptibility to infection that mirror observed trends in experimental infections of mice and of humans exposed to infection in areas of endemic transmission. The heterogeneity in outcome predicted by the model can arise either through differences in the values of the parameters that characterize the genetic background of the host or as a consequence of differences in the size of the infecting inoculum of the parasite. Detailed analyses of equilibrium states and of the time course of infection within a host suggest that a limitation in the availability of precursor T-cells, as a consequence of high levels of recruitment into the activated pool, may play a significant role in the progression of infection in susceptible hosts. A brief discussion is presented of the implications of model prediction for therapeutic intervention.

Animals↗
PubMed1993

Colloid cyst of the 3rd ventricle as a cause of acute neurological deterioration and sudden death.

A 13 year old girl presented with a 24 h history of headache and vomiting. There were no focal neurological signs. The diagnoses considered were vascular headache, meningitis and subarachnoid haemorrhage. Lumbar puncture revealed clear cerebrospinal fluid under high pressure and subsequent cerebral computed tomography (CT) scan revealed hydrocephalus. Death occurred some hours after the lumbar puncture. Autopsy revealed a colloid cyst of the 3rd ventricle causing the hydrocephalus. Cerebellar tonsillar herniation was present. This case is reported because although 3rd ventricular colloid cysts are a recognized cause of acute neurological deterioration and sudden death, they rarely present in childhood. In this case, it is considered that lumbar puncture may have hastened death by increasing brain-stem compression due to cerebellar tonsillar herniation. It raises the question of whether cerebral CT scan, where readily available, should be performed prior to lumbar puncture. Pathologically, colloid cysts may be easily missed if the brain is examined fresh as the cysts are fragile and have a tendency to be destroyed or fall out.

Adolescent↗