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PubMed2000

Pest control by the release of insects carrying a female-killing allele on multiple loci.

With recent advances in genetics, many new strategies for pest control have become feasible. This is the second article in which we model new techniques for pest control based on the mass release of genetically modified insects. In this article we model the release of insects carrying a dominant and redundant female killing or sterilizing (FK) allele on multiple genetic loci. If such insects are released into a target population, the FK allele can become widely spread in the population through the males while reducing the population each generation by killing females. We allow the number of loci used to vary from 1 to 20. We also allow the FK allele to carry a fitness cost in males due to the gene insertions. Using a model, we explore the effectiveness and optimal strategies for such releases. In the most ideal circumstances (no density-dependence and released insects equal in fitness to wild ones), FK releases are several orders of magnitude more effective than equal sized sterile male releases. For example, a single release of 19 FK-bearing males for every two wild males, with the released males carrying the FK allele on 10 loci, reduces the target population to 0.002% of no-release size. An equal sized sterile release reduces the target population to 5% of no-release size. We also show how the effectiveness of the technique decreases as the fitness cost of the FK alleles in males increases. For example, the above mentioned release reduces the target population to 0.7% of no-release size if each FK allele carries a fitness cost in males of 5%. Adding a simple model for density-dependence and assuming that each of the released males carries the FK allele on six loci, we show that the release size necessary to reduce the target population to 1/100 of no-release size in 10 generations of releases varies from 0.44:1 to 4:1 (depending on parameter values). We also calculate the optimal number of loci on which to put the FK allele under various circumstances.

Alleles↗

PubMed2002

On the standardisation of the twinning rate.

In many studies the twinning rate, being strongly dependent on maternal age (and parity), has been standardised according to the maternal age distribution. The direct method requires very informative twinning data for the target population. The indirect method is used when the data for the target population is not sufficiently informative or when the target population is small. We have earlier introduced an alternative indirect technique for standardising the twinning rate. Our technique requires even less of the twinning data. Besides maternal age, parity is an influential factor, and should, if possible, be taken into account. In this study we present the traditional standardisation methods based on both maternal age and parity, we propose a new direct standardisation method and we develop our standardisation methods so that they take into account both maternal age and parity. We apply these standardisation methods to data from Finland, 1953-1964, from St. Petersburg, Russia, 1882-92, from Canada 1952-1967, and from Denmark, 1896-1967. These methods all give results very similar to those for the Finnish data, but the effect of parity is strongest with the direct methods. This may be due to the fact that, among extramarital maternities, parity has a strongly increasing effect on the twinning rate. This may be attributed to a higher reproduction capacity among unmarried mothers. Standardisations of the Canadian and the Danish data also give reliable results. With the St. Petersburg data, however, the different standardisations show notable discrepancies. These discrepancies are compared with Allen's findings.

Canada↗

PubMed2001

A venue-based method for sampling hard-to-reach populations.

Constructing scientifically sound samples of hard-to-reach populations, also known as hidden populations, is a challenge for many research projects. Traditional sample survey methods, such as random sampling from telephone or mailing lists, can yield low numbers of eligible respondents while non-probability sampling introduces unknown biases. The authors describe a venue-based application of time-space sampling (TSS) that addresses the challenges of accessing hard-to-reach populations. The method entails identifying days and times when the target population gathers at specific venues, constructing a sampling frame of venue, day-time units (VDTs), randomly selecting and visiting VDTs (the primary sampling units), and systematically intercepting and collecting information from consenting members of the target population. This allows researchers to construct a sample with known properties, make statistical inference to the larger population of venue visitors, and theorize about the introduction of biases that may limit generalization of results to the target population. The authors describe their use of TSS in the ongoing Community Intervention Trial for Youth (CITY) project to generate a systematic sample of young men who have sex with men. The project is an ongoing community level HIV prevention intervention trial funded by the Centers for Disease Control and Prevention. The TSS method is reproducible and can be adapted to hard-to-reach populations in other situations, environments, and cultures.

Adolescent↗

PubMed1998

Gains in life expectancy from medical interventions--standardizing data on outcomes.

BACKGROUND: The gain in life expectancy is an important measure of the effectiveness of medical interventions, but its interpretation requires that it be placed in context. The interpretation of gains in life expectancy is particularly problematic for preventive interventions, for which the gains are often just weeks or even days when averaged across the entire target population. METHODS: We tabulated the gains in life expectancy from a variety of medical interventions as reported in 83 published sources and categorized them according to target population and disease. We considered prevention in populations at average risk for particular diseases, prevention in populations at elevated risk, and treatments in populations with established disease. RESULTS: The gains in life expectancy from preventive interventions in populations at average risk ranged from less than one month to slightly more than one year per person receiving the intervention, but the gains were as high as five years or more if the prevention was targeted at persons at especially high risk. The gains in life expectancy from treatments of established disease ranged from several months (for coronary thrombolysis and revascularization to treat heart disease) to as long as nine years (for chemotherapy to treat advanced testicular cancer). CONCLUSIONS: A gain in life expectancy from a medical intervention can be categorized as large or small by comparing it with gains from other interventions aimed at the same target population. A gain in life expectancy of a month from a preventive intervention targeted at populations at average risk and a gain of a year from a preventive intervention targeted at populations at elevated risk can both be considered large. The framework we developed for standardizing gains in life expectancy can be used in the interpretation of data on the outcomes of interventions.

Adolescent↗

PubMed2003

Reducing disparities in utilization of mamography: reaching dually eligible women in Connecticut.

This article describes a two-pronged intervention by the health care Quality Improvement Organization (QIO) for Connecticut to address the disparity in rates of mammography screening between women eligible for both Medicare and Medicaid (i.e., "dually eligible") and other Medicare beneficiaries. The interventions were directed beneficiaries. One intervention addressed information and access needs of the target population: an education session was followed by a mobile mammography van session at low-income housing sites in specific geographic areas. The second intervention was a culturally-sensitive direct mailing to dually eligible beneficiaries across the state. Implementation methods are described including: defining and identifying the target population; specifying the disparity; developing community collaboration; and testing the mail materials. Preliminary results of the education sessions and community testing of the direct mail materials generated information about the target population. Issues in implementation and analysis include: reaching the target population, building community relations, and developing design approaches to test the intervention.

Aged↗

PubMed1991

Implementation of mass media community health education: the Forsyth County Cervical Cancer Prevention Project.

The Forsyth County Cervical Cancer Prevention Project (FCP) is a community-based health education project funded by the National Cancer Institute. The target population includes around 25 000 black women age 18 and older who reside in Forsyth County, North Carolina. The overall goal of the program is to prevent mortality from cervical cancer by promoting Pap smears and return for follow-up care when needed. Based on the principles of social marketing, a plan to reach the target population with mass media educational messages through electronic and print channels was developed. Guided by marketing objectives, the target population was divided into relatively discrete segments. The segments included church attenders, patients in waiting rooms of public and selected health providers, female students at local colleges, shoppers, viewers of radio and television, newspaper readers, and business owners and managers. Introduction of the program was based on strategies developed for reaching the target population in each segment with television, radio and print mass media messages. Qualitative assessment of the mass media developed by the program indicated that all forms of communication helped to increase awareness of the program.

Adolescent↗

PubMed1993

Design of clinical radiologic research.

The components of clinical research design--the research question, the review of prior research, the study design, the study subjects, the study measurements, the statistical analysis, and the critical analysis--have been discussed. These components relate to the overall philosophy of the research process in the following manner. The driving force behind research is the desire to understand a universal truth (Fig. 6). The research question is formed to reflect the truth sought. Next defined is the specific target population and the phenomena of interest with regard to the sought-after truth. The study is then designed with a study plan detailing timing and location and an intended sample population chosen to reflect the target population. The phenomena of interest are translated into measurable intended variables. Care is needed to identify the systematic error that can be introduced at this stage; outside opinion can be invaluable. The actual study results from the implementation of the study design. The actual subjects may differ from the intended sample population due to a low recruitment rate or a large dropout rate. The actual measurements may differ from the intended variables due to unsuspected confounding variables or random errors. Statistical analysis is performed on the study findings to infer truth within the study. This truth may be affected by random and systematic errors in implementing the study. Truth in the study is then inferred to reflect truth in the universe. Systematic and random errors in study design may affect the validity of that deduction, but that deduction is the only way we have of understanding universal truth.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiology↗

PubMed2005

Improved estimation of controlled direct effects in the presence of unmeasured confounding of intermediate variables.

Adjusting for a causal intermediate is a common analytic strategy for estimating an average causal direct effect (ACDE). The ACDE is the component of the total exposure effect that is not relayed through the specified intermediate. Even if the total effect is unconfounded, the usual ACDE estimate may be biased when an unmeasured variable affects the intermediate and outcome variables. Using linear programming optimization to compute non-parametric bounds, we develop new ACDE estimators for binary measured variables in this causal structure, and use root mean square confounding bias (RMSB) to compare their performance with the usual stratified estimator in simulated distributions of target populations comprised of the 64 possible potential response types as well as distributions of target populations restricted to subsets of 18 or 12 potential response types defined by monotonicity or no-interactions assumptions of unit-level causal effects. We also consider target population distributions conditioned on fixed outcome risk among the unexposed, or fixed true ACDE in one stratum of the intermediate. Results show that a midpoint estimator constructed from the optimization bounds has consistently lower RMSB than the usual stratified estimator both unconditionally and conditioned on any risk in the unexposed. When conditioning on true ACDE, this midpoint estimator performs more poorly only when conditioned on an extreme true ACDE in one stratum of the intermediate, yet outperforms the stratified estimator in the other stratum when interaction is permitted. An alternate 'limit-modified crude' estimator can never perform less favourably than the stratified estimator, and often has lower RMSB.

Bias↗

PubMed1978

Health service coverage and its evaluation.

Health service coverage is considered as a concept expressing the extent of interaction between the service and the people for whom it is intended, this interaction not being limited to a particular aspect of service provision but ranging over the whole process from resource allocation to achievement of the desired objective. For the measurement of coverage, several key stages are first identified, each of them involving the realization of an important condition for providing the service; a coverage measure is then defined for each stage, namely the ratio between the number of people for whom the condition is met and the target population, so that a set of these measures represents the interaction between the service and the target population. This definition of coverage allows for variations, which are called "specific coverage", by limiting the target population to specific subgroups differentiated by certain conditions related to service provision or by demographic or socioeconomic factors.The evaluation of coverage on the basis of these concepts enables management to identify bottlenecks in the operation of the service, to analyse the constraining factors responsible for such bottlenecks, and to select effective measures for service development.

Cost-Benefit Analysis↗

PubMed2001

[Implementation and evaluation of public relations activity in a community health program].

OBJECTIVE: This study evaluated public relations activity in a community health program in order to develop effective strategies to attract the public attention for the program. METHODS: An intervention study was conducted on public relations for "Nutrition Seminar for Citizens," sponsored by the Health Department of Machida City, Tokyo, in October, 1999. One ward in the city was selected as an intervention area, and another ward which had similar demographic and geographic characteristics was chosen as a control area. Two target populations were defined; one was women in their 20s to 60s (#1) and the other was those who had previously never utilized community health programs sponsored by the city (#2). Handbills were used as the medium for public relations for the seminar. These announced the time, place and content of the nutrition seminar and were designed by authors with special attention to catchphrases, colors and fonts. Handbills were distributed in the intervention area through elementary schools, local voluntary organizations and local health volunteers. In addition, the authors directly handed them out to people in front of two supermarkets in the town. The sources of seminar information were requested from the participants of the Nutrition Seminar with a self-administered questionnaire. RESULTS: 1. The percentage of participants who received the seminar information from handbills was higher than that of those who used monthly newsletters from the city as a source of information. 2. The percentage of participants from the intervention area was higher than that from the control area. 3. Regarding target populations #1 and #2, there were no differences in participation rates between the intervention and control area. 4. Among the four distribution routes, the local voluntary organization route was the most effective for attracting participants. CONCLUSIONS: The results show that handbills can be an effective medium for pubic relations to increase the number of participants in community health programs. Also, local voluntary organizations can play a crucial role in information transfer in the community because of their high credibility. On the other hand, we could not reach specified target populations with the medium. Further surveys are needed to establish optimal media and routes to reach appropriate target populations in health programs.

Adult↗

PubMed2003

Cumulative risk and population attributable fraction in prevention.

Compares the use of relative risk versus population attributable fraction in determining the target population for multirisk prevention programs in psychology. Results show that relative risk generally increases as a function of cumulative risk. Guided by this measure, prevention programs should target populations with the largest cumulative risk. However, relative risk does not account for the prevalence of a particular level of cumulative risk in the population. Therefore, because the largest cumulative risk is experienced by only a small portion of the population, prevention programs guided by this measure will not always have the greatest public health benefit to reduce the incidence of problem outcomes in the population. On the other hand, the population attributable fraction, which does take into account the prevalence of a particular level of cumulative risk, does not increase appreciably after a cumulative risk of one, two, or three because the majority of people in the population will experience these levels of cumulative risk. Guided by this measure, prevention programs that target the higher proportion of people who have a more moderate level of risk would have the maximum impact on the population. National data sets from Great Britain (the British Births Cohort Study [BCS]) and the United States (National Longitudinal Study of Youth [NLSY]) are used to explore this pattern of effects.

Adolescent↗

PubMed2005

Diabetes-related symptoms and negative mood in participants of a targeted population-screening program for type 2 diabetes: The Hoorn Screening Study.

OBJECTIVE: To determine the level of diabetes-related symptom distress and its association with negative mood in subjects participating in a targeted population-screening program, comparing those identified as having type 2 diabetes vs. those who did not. RESEARCH DESIGN AND METHODS: This study was conducted within the framework of a targeted screening project for type 2 diabetes in a general Dutch population (age 50-75 years). The study sample consisted of 246 subjects, pre-selected on the basis of a high-risk profile; 116 of whom were subsequently identified as having type 2 diabetes, and 130 who were non-diabetic subjects. Diabetes-related symptom distress and negative mood was assessed approximately 2 weeks, 6 months, and 12 months after the diagnosis of type 2 diabetes, with the Type 2 Diabetes Symptom Checklist and the Negative well-being sub scale of the Well-being Questionnaire (W-BQ12), respectively. RESULTS: Screening-detected diabetic patients reported significantly greater burden of hyperglycemic (F = 6.0, df = 1, p = 0.015) and of fatigue (F = 5.3, df = 1, p = 0.023) symptoms in the first year following diagnosis type 2 diabetes compared to non-diabetic subjects. These outcomes did not change over time. The total symptom distress (range 0-4) was relatively low for both screening-detected diabetic patients (median at approximately 2 weeks, 6 months, and 12 months; 0.24, 0.24, 0.29) and non-diabetic subjects (0.15, 0.15, 0.18), and not significantly different. No average difference and change over time in negative well-being was found between screening-detected diabetic patients and non-diabetic subjects. Negative well-being was significantly positive related with the total symptom distress score (regression coefficient beta = 2.86, 95% CI 2.15-3.58). CONCLUSIONS: The screening-detected diabetic patients were bothered more by symptoms of hyperglycemia and fatigue in the first year following diagnosis type 2 diabetes than non-diabetic subjects. More symptom distress is associated with increased negative mood in both screening-detected diabetic patients and non-diabetic subjects.

Affect↗

PubMed2004

[The cross-cultural adaptation to Portuguese of the Dissociative Experiences Scale for screening and quantifying dissociative phenomena].

OBJECTIVE: This paper presents the cross-cultural adaptation to Portuguese of the Dissociative Experiences Scale, the worldwide most employed questionnaire for screening and quantifying dissociative phenomena. METHODS: Two translations and their respective back-translations were performed, as well as the evaluation of the semantic equivalence, the preparation of the synthetic version, the pre-testing on the target population, the definition of the final version and a second pre-testing on the target population. RESULTS: A high level of semantic equivalence between the original instrument and the two pairs of translations and back-translations was observed regarding the referential and general meanings. The two pre-testing in the target population led to alterations in order to achieve the semantic and operational equivalence criteria. CONCLUSION: This work provides the first adaptation of a specific instrument to detect and quantify dissociative symptoms in the Brazilian context.

Cross-Cultural Comparison↗

PubMed1996

Using formative research to lay the foundation for community level HIV prevention efforts: an example from the AIDS Community Demonstration Projects.

The AIDS Community Demonstration Projects provided community-level HIV prevention interventions to historically hard-to-reach groups at high risk for HIV infection. The projects operated under a common research protocol which encompassed formative research, intervention delivery, process evaluation, and outcome evaluation. A formative research process specifically focusing on intervention development was devised to assist project staff in identifying, prioritizing, accessing, and understanding the intervention target groups. This process was central to the creation of interventions that were acceptable and unique to the target populations. Intended to be rapid, the process took 6 months to complete. Drawn from the disciplines of anthropology, community psychology, sociology, and public health, the formative research process followed distinct steps which included (a) defining the populations at high-risk for HIV; (b) gathering information about these populations through interviews with persons who were outside of, but who had contact with, the target groups (such as staff from the health department and alcohol and drug treatment facilities, as well as persons who interacted in an informal manner with the target groups, such as clerks in neighborhood grocery stores and bartenders); (c) interviewing people with access to the target populations (gatekeepers), and conducting observations in areas where these high-risk groups were reported to gather (from previous interviews); (d) interviewing members of these groups at high risk for HIV infection or transmission; and (e) systematically integrating information throughout the process. Semistructured interview schedules were used for all data collection in this process. This standardized systematic method yielded valuable information about the focal groups in each demonstration project site. The method, if adopted by others, would assist community intervention specialists in developing interventions that are culturally appropriate and meaningful to their respective target populations.

Acquired Immunodeficiency Syndrome↗

PubMed2001

Interventions for preventing obesity in children.

BACKGROUND: The prevalence of obesity and overweight is increasing world-wide. Obesity in children impacts on their health in both the short and longer term. Obesity prevention strategies are poorly understood. OBJECTIVES: To assess the effectiveness of interventions designed to prevent obesity in childhood. SEARCH STRATEGY: Electronic databases were searched from 1985 to October 1999. SELECTION CRITERIA: Data from RCTs and non-randomised trials with concurrent control group were included. studies with follow up of one year minimum were selected, A priori, this was subsequently amended to include studies with minimum follow up of three months. The possible susceptibility of post hoc questions to bias is addressed. DATA COLLECTION AND ANALYSIS: Two reviewers independently extracted data and assessed study quality. MAIN RESULTS: Seven studies were included, three long-term and four short- term. The studies included were diverse in terms of study design and quality, target population, theoretical underpinning of intervention approach, and outcome measures. As such, it was not possible to combine study findings using statistical methods. REVIEWER'S CONCLUSIONS: The findings of the review suggest that currently there is limited quality data on the effectiveness of obesity prevention programs and as such no generalisable conclusions can be drawn. The need for well-designed studies which examine a range of interventions remains a priority.

Adolescent↗

PubMed1999

Mammography requests in general practice during the introduction of nationwide breast cancer screening, 1988-1995.

Introducing an organised breast cancer screening programme for certain age groups in a population might induce opportunistic screening in adjacent (non-invited) age groups and influence health behaviour in the target population. We analysed the effect of the start of the Dutch national screening programme on the number of mammographies requested by 43-45 general practices for the age groups 30-39, 40-49, 50-69 and 70+ years, using logistic regression analysis. In all age groups an immediate increase was observed in the number of mammography requests after the start of the screening, which was largest and statistically significant in the target population of the screening programme (age 50-69 years). More than 2 years after the start of screening, the number of mammography requests in all age groups had decreased to the level before the start and in the age group 50-69 years the number of mammographies was significantly lower than before the screening started. The unexpected increase in mammographies after the start of the breast cancer screening programme might be related to registry problems or to the process of building up the screening programme. Eventually there was a decrease in the number of mammographies in the target population, probably an effect of the introduction of the national screening programme. Opportunistic screening was not clearly demonstrated in adjacent age groups.

Adult↗

PubMed2025

Prediction of Australian wheat genotype by environment interactions and mega-environments.

Latent environmental effects of genotype by environment interactions could be predicted from observed environmental covariates. Predictions into the wider target population of environments revealed greater insights. Wheat is grown across a diverse range of environments in Australia with contrasting environmental constraints. Targeted breeding to optimise genotypes in target environments is hindered by large and ubiquitous genotype by environment interactions (GEI). Common GEI in multi-environment trial experiments, which sample the target population of environments, can be efficiently modelled using latent environmental effects from factor analytic mixed models. However, generalised prediction into the full target population of environments is difficult without a clear link to observed environmental covariates (ECs) that are defined from high-resolution weather and soil data. Here, we used a large wheat multi-environment trial dataset and demonstrated that latent environmental effects can be associated with and predicted from observed ECs. We found GEI-based environment classes could be defined by combinations of key ECs. Prediction of main and latent effects in a wider set of environments covering the full TPE across the Australian grain belt over 13 years revealed the complex trends of environmental effects and GEI over regional scales demonstrating high year-to-year variability. Regional environment types often shifted year-to-year. Cross-validation of forward genomic prediction into untested year environments demonstrated that increased accuracy is possible if estimated genetic effects are also accurate and ECs of new environments are known. These findings may guide Australian wheat breeders to better target specifically adapted material to mega-environments defined by static GEI while also considering broad adaptability and non-static GEI resulting from year-to-year variability.

Triticum↗

PubMed2003

Estimating prevalence of problem drug use at national level in countries of the European Union and Norway.

OBJECTIVES: This paper will present the most recent estimates for problematic drug use in European Member States and explore the problems of comparability. METHODS: Estimates of problematic drug use, derived according to agreed guidelines, were collected from all EU countries and Norway. Methods included multipliers based on treatment, police, mortality or AIDS/HIV data, the capture-recapture method and the multivariate indicator method. Prevalence estimates were transformed into rates per 1000 population aged 15-64 years. RESULTS: Target populations varied according to data selection. Estimates for six partially overlapping types of drug use could be identified: 'problem opiate use', 'problem opiate or cocaine use', 'problem amphetamine or opiate use', 'problem drug use', '(current) injecting' and 'life-time injecting'. Rates of injectors ranged from 2.6 in Germany to 4.8 in Luxembourg; rates in Austria, Denmark, Finland, Portugal and the United Kingdom fell within this range. For problem opiate use, a group of high prevalence countries were found with average rates exceeding six cases (Italy, Luxembourg, Spain and the United Kingdom) and a group with lower prevalence with average rates close to three cases (Austria, Germany, Ireland, the Netherlands). Rates obtained for France (problem opiate or cocaine use), Finland and Sweden (problem amphetamine or opiate use) are not directly comparable and fall between these rates. CONCLUSIONS: Cross-national comparisons should be made with care and estimated target populations may vary greatly between countries. For estimating various forms of problem drug use at national level, a multi-method approach is recommended.

Epidemiologic Methods↗