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Biomedical subjects

R Trotter

Publications and source records attributed to R Trotter.

10 recordsLinked to original sources
PubMed2001

The risk environment for HIV transmission: results from the Atlanta and Flagstaff network studies.

The purpose of this study was to investigate the hypothesis that human immunodeficiency virus (HIV) transmission may be facilitated or obstructed by network structure, incorporating a measure of risk that combines true risk and surrogates. Persons at presumed high risk for HIV were enrolled in long-term follow-up studies of urban and rural networks in Atlanta, Georgia, and Flagstaff, Arizona. We focused on respondents who were also contacts to evaluate information on both sides of the observed dyads and constructed a Risk Indicator, based on a four-digit binary number, that permitted assessment and visualization of the overall risk environment. We constructed graphs that provided visualization of the level of risk, the types of relationships, and the actual network. Although some of the findings conform to the hypotheses relating network structure to transmission, there were several anomalies. In Atlanta, HIV prevalence was most strongly related to men with a male sexual orientation, despite the widespread use of injectable drugs. In Flagstaff, an area of very low prevalence and no transmission, the risk environment appeared more intense, and the frequency of microstructures was as great or greater than representative areas in Atlanta. The network hypothesis is not yet sufficiently developed to account for empirical observations that demonstrate the presence of intense, interactive networks in the absence of transmission of HIV.

Adult↗
PubMed2000

Unemployment, drug use, and HIV risk among American Indian and Alaska Native drug users.

American Indians and Alaska Natives have had low employment in recent history. Drug users also have low employment due to cycles of drug use and relapse,and the impact of the type of drug abused on levels of functioning. Drug use is associated with increased HIV risk through injection drug use, frequency of injection, and needle sharing. Data from three sites of the NIDA Cooperative Agreement for Community Based-Outreach/Intervention Research were analyzed to determine the relationship among race/ethnicity, age, and level of educational attainment on employment and unemployment at intake interview and six-month follow-up. HIV risk for those employed and unemployed was then assessed. American Indian and Alaska Native drug users were younger, less educated, and less likely to have a paid job at both intake and follow-up than non-Native drug users. Those participants who were unemployed at baseline interview who were American Indian/Alaska Native were less likely to transition to employment at six-month follow-up than other race/ethnicity groups in the cohort. However, all participants showed low levels of employment at follow-up. Individuals who were employed at baseline and those who transitioned to employment had lower levels of injection drug use and needle sharing than those who were unemployed at both baseline and follow-up. American Indian and Alaska Native drug users may be at risk for acquisition of HIV due to drug risk behaviors that appear to be associated with unemployment.

Adult↗
PubMed1999

Multiple-informant ranking of the disabling effects of different health conditions in 14 countries. WHO/NIH Joint Project CAR Study Group.

BACKGROUND: The Global Burden of Disease study provided international statistics on the burden of diseases, combining mortality and disability, that can be used for priority setting and policy making. However, there are concerns about the universality of the disability weights used. We undertook a study to investigate the stability of such weighting in different countries and informant groups. METHODS: 241 key informants (health professionals, policy makers, people with disabilities, and their carers) from 14 countries were asked to rank 17 health conditions from most disabling to least disabling. Kruskal-Wallis ANOVA was used to test for differences in ranking between countries or informant groups and Kendall tau-B correlations to measure association between different rank orders. FINDINGS: For 13 of 17 health conditions, there were significant (p<0.05) differences in ranking between countries; in the comparison of informant groups, there were significant differences for five of the 17 health conditions. The overall rank order in the present study was, however, almost identical to the ranking of the Global Burden of Disease study, which used a different method. Most of the rank correlations between countries were between 0.50 and 0.70 (average 0.61 [95% CI 0.59-0.64]). The average correlation of rank orders between different informant groups was 0.76. INTERPRETATION: Rank order of disabling effects of health conditions is relatively stable across countries, informant groups, and methods. However, the differences are large enough to cast doubt on the assumption of universality of experts' judgments about disability weights. Further studies are needed because disability weights are central to the calculation of disability-adjusted life years.

Analysis of Variance↗
PubMed1998

HIV risk behaviors associated with the injection process: multiperson use of drug injection equipment and paraphernalia in injection drug user networks.

This study examines drug acquisition and multiperson use of paraphernalia, drugs, and needles/syringes. Ethnographers observed 54 injection episodes in which IDUs were linked by HIV risk behaviors, and developed a typology of higher-risk, lower-risk, and nonsharing-risk networks. Multiperson use of injection paraphernalia or drug solution occurred in most injection events (94%). Serial use of syringes/needles occurred infrequently (14%) relative to "backloading" (37%) and reuse of paraphernalia (cookers 84%, cotton 77%, water 77%). Higher-risk injection networks were characterized by larger size and pooling of resources for drugs. Prevention messages must include avoiding reuse of injection paraphernalia and transfer of drug solution.

Anthropology, Cultural↗
PubMed1995

HIV risk in intravenous drug users and crack cocaine smokers: predicting stage of change for condom use.

This study examined the utility of the Transtheoretical Model of Change and the AIDS Risk Reduction Model for predicting condom use with not-in-treatment crack cocaine smokers and intravenous drug users. The sample included 265 participants; 99 reported having casual partners and 166 reported having main partners. All participants must have used drugs in the preceding 48 hr and received no drug treatment for at least 1 year. Participants were grouped into 3 stages of change; precontemplation, contemplation, and action. Logistic regression analyses indicated that both the benefits of change and condom assertiveness varied across the stages of change for main and casual partners, whereas the costs of change were important for predicting stage only with main partners. Age was a significant predictor of stage with casual partners, whereas ethnicity and nonherpes sexually transmitted diseases significantly predicted stage with main partners. The utility of the stages of change for choosing intervention strategies and the need for more qualitative and longitudinal research to determine additional predictors of intention to use condoms are discussed.

Adolescent↗
PubMed1994

Head and neck tumors after energetic proton irradiation in rats.

This is a two-year progress report on a life span dose-response study of brain tumor risk at moderate to high doses of energetic protons. It was initiated because a joint NASA/USAF life span study of rhesus monkeys that were irradiated with 55-MeV protons (average surface dose, 3.5 Gy) indicated that the incidence of brain tumors per unit surface absorbed dose was over 19 times that of the human tinea capitis patients whose heads were exposed to 100 kv x-rays. Examination of those rats that died in the two-year interval after irradiation of the head revealed a linear dose-response for total head and neck tumor incidence in the dose range of 0-8.5 Gy. The exposed rats had a greater incidence of pituitary chromophobe adenomas, epithelial and mesothelial cell tumors than the unexposed controls but the excessive occurrence of malignant gliomas that was observed in the monkeys was absent in the rats. The estimated dose required to double the number of all types of head and neck tumors was 5.2 Gy. The highest dose, 18 Gy, resulted in high mortality due to obstructive squamous metaplasia at less than 50 weeks, prompting a new study of the relative biological effectiveness of high energy protons in producing this lesion.

Adenoma↗
PubMed1988

Experimental Rift Valley fever in rhesus macaques.

Rift Valley fever (RVF) is a major cause of human morbidity and mortality in endemic areas of sub-Saharan Africa and has the potential to cause epidemic disease in receptive areas world-wide. In this study, a RVF viral isolate from the 1977 Egyptian epidemic (ZH-501) inoculated intravenously into rhesus macaques caused a benign viremic infection in most, but resulted in the hemorrhagic fever syndrome in 20 per cent (3 of 15). Serious disease of this type has not previously been observed in nonhuman primates inoculated with RVF virus and may be a consequence of the viral strain used or the route of inoculation. Severe disease was accompanied by extensive liver necrosis, disseminated intravascular coagulation, and microangiopathic hemolytic anemia. We also attempted to prevent RVF by passive transfer of serum from vaccinated rhesus monkeys (plaque-reduction neutralization test titer 1:2,560). As little as 0.025 ml/kg prevented the development of viremia in naive rhesus monkeys after subcutaneous inoculation of virus. The monkey model should be helpful in understanding the pathogenesis and prevention of human RVF.

Animals↗