Cocaine abuse and acquired immunodeficiency syndrome: a tale of two epidemics.
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Acquired Immunodeficiency Syndrome↗
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Results for “Effect Modifier, Epidemiologic”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
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Memory improvements and pharmacological treatment: a method to distinguish direct effects on memory from secondary effects due to attention improvement.
Chronic cerebrovascular disturbances of the aged are characterized by a decline of attention. When these patients undergo pharmacological treatment, it is very difficult to distinguish between a direct benefit and/or a secondary effect on memory resulting from attention improvement. In our study we have proposed and evaluated a new method for identifying the different components of therapeutic efficacy on memory and attention in chronic cerebrovascular patients. This method is based on the use of the Randt Memory Test, traditional scores of memory efficiency (Acquisition, Recall, and a combined index), and the RMT three-factor scores derived from a structural model of memory functioning. The three scores have been called Encoding and Organization, Cognitive Efficiency, and Attention Efficiency. Participants were 96 selected chronic cerebrovascular patients treated in a double-blind study for 12 weeks with dihydroergocristine versus placebo. While changes in both acquisition and recall scores were related to the treatment, only changes of the Encoding and Organization factor scores were systematically related to therapy. Changes in Attention Efficiency were positively related to therapy only in proportion to the degree of cerebrovascular impairment.
Attention↗
Extrapolating from toxicity data to occupational exposure limits: some considerations.
This paper evaluates procedures relevant to extrapolating from toxicity data in man and animals to Occupational Exposure Limits. It examines effects at or around the "No Observed Adverse Effect Level' (NOAEL) and the magnitude of safety factors which can be applied in developing occupational exposure limits for non-stochastic effects. The relationship between incidence of stochastic effect and occupational exposure limit is also discussed.
Clinical Protocols↗
On randomized controlled trials and lifestyle interventions.
Randomized controlled trials (RCT) are viewed as the ultimate method for evaluation. The author claims that RCT do not enable full evaluation of lifestyle interventions in particular. Lifestyle interventions usually affect several diseases not measured by RCTs and the people who have undergone these interventions also have an impact on the lifestyle in their immediate environment. These potential biases indicate that RCTs underestimate the value of lifestyle interventions.
Bias↗
Aging and total cholesterol levels: cohort, period, and survivorship effects.
This analysis describes the association of age with the serum total cholesterol level in 5,010 participants in a geriatric health screening program. Cholesterol levels were measured annually in participants monitored for up to 12 years. The association of age with cholesterol level is described via three approaches: cross-sectional analysis, descriptive longitudinal analysis, and longitudinal analysis using statistical modeling. The results were compared to examine the influence of cohort, period, and survivorship effects on the association between age and cholesterol. In cross-sectional analysis, the cholesterol level was fairly constant for the ages of 65 to 75 years, but decreased by 21% over the age range from 75 to 95 years. Descriptive longitudinal analysis suggested that both cohort and period effects were influencing the cross-sectional findings. In longitudinal analysis adjusting for both cohort and period effects, the findings were similar to those from cross-sectional analysis for the ages of 65 to 75 years, but from the ages of 75 to 95 years, cholesterol decreased by only 9%--half as great a decline as that estimated from cross-sectional analysis. When longitudinal data were limited to those with complete follow-up, the predicted decline for the age range from 75 to 95 years was only 6%. Although this flattening of the age trend was suggestive, there was no conclusive evidence that it reflected an association between baseline cholesterol and loss to follow-up.
Age Factors↗
Tap or bottled water consumption and spontaneous abortion: a 1986 case-control study in California.
To investigate whether drinking tap or bottled water during pregnancy affects the risk of spontaneous abortion, we asked questions about water consumption in a large case-control study (626 cases, 1,300 controls). The study ascertained cases from hospital pathology laboratory reports of pregnancies that began in 1986 and obtained controls from birth certificates. The crude odds ratio for consumption of any vs no cold tapwater at home during the first trimester was 1.2 (95% confidence interval = 1.0-1.5), with no dose-response effect. The crude odds ratio for any bottled water consumption was 0.79 (95% confidence interval = 0.65-0.96), with a downward trend by amount consumed. Adjusting for many potential confounders did not alter these associations appreciably, although some variables appeared to be effect modifiers. The point estimates were stronger among women who were more difficult to contact, suggesting the possibility of bias.
Abortion, Spontaneous↗
Just another day in a woman's life? Part II: Nature and consistency of women's long-term memories of their first birth experiences.
Twenty women who attended the author's natural childbirth classes between 1968 and 1974 were the informants in this study of long-term memories of their first childbirths. The data from each informant consisted of 1) a labor and birth questionnaire, including an open-ended account of her labor, written shortly after her baby was born; 2) a similar questionnaire and account written in 1988 and 1989; and 3) a transcribed interview during which her memories and perceptions were discussed and any discrepancies between the questionnaires were explored. The questionnaires were compared for consistency of recall, and the interviews consulted for further clarification. Specific memories were excerpted, compared, classified, tabulated, and summarized. Findings were that, years later, women's memories are generally accurate, and many are strikingly vivid, especially of onset of labor; rupture of the membranes; arrival at the hospital; actions of doctors, nurses, and partners; particular interventions; the birth; and first contact with the baby. Most memory lapses or confusion were minor. Evidence of a halo effect was observed as well.
Adaptation, Psychological↗
Nursing homes and tranquilizer use among the institutionalized elderly.
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Effect Modifier, Epidemiologic↗
The effect of a five-month delay on children's and adults' eyewitness memory.
Child witnesses must endure a delay of around six months between observing or being the victim of an alleged offence and being required to give evidence in a criminal court. While the legal profession seem to believe that young children's memories are particularly sensitive to the passage of time, developmental psychology can offer little relevant data to support or refute this presumption. In the present study, children aged six and nine years and adults witnessed a staged event and were subsequently interviewed in the days following the event and/or five months later. Results indicate that while all witnesses forgot information over this period, the younger children (six years) recalled slightly less information than the older children and the adults. The total amount of incorrect information recalled did not increase over the same period. Two different interviewing techniques were used--cued recall vs. 'enhanced' recall--the latter incorporating some aspects of the cognitive interview procedure. No differences were found relating to the interview techniques employed. The results underline the importance of recording initial interviews with child witnesses wherever possible.
Adult↗
Postal survey on airborne occupational exposure and respiratory disorders in Norway: causes and consequences of non-response.
STUDY OBJECTIVE: The aim was to examine causes for non-response in a community survey, and how non-response influences prevalence estimates of some exposure and disease variables, and associations between the variables. DESIGN: This was a cross sectional questionnaire study with two reminder letters. The questionnaire asked for information on smoking habits, occupational airborne exposure and respiratory disorders. SETTING: A random sample of 4992 subjects from the general population aged 15-70 years of Hordaland County, Norway. MAIN RESULTS: The overall response rate was 90%, with a 63% response to the initial letter. The response rates to the first and second reminder letters were 56% and 36% respectively. In 20% of the non-respondents an uncompleted questionnaire was returned with cause for non-response; in two thirds of these the cause for non-response was that the subject was not resident at the mailing address. A home visit to a random sample of 50 urban non-respondents provided further information on 29 subjects. A wrong address at the Central Population Registry and the subject's feeling of lack of personal benefit from a postal survey were the major reasons for non-response. Smokers were late respondents and subjects with respiratory disorders tended to be early respondents. CONCLUSION: The main reasons for non-response were a wrong mailing address and a feeling of lack of personal benefit from responding. Using only the initial letter would have changed the estimated prevalence of smokers from 39% to 35%. Otherwise, the estimated prevalence of the exposure and disease variables as well as the associations between them were only slightly changed after including the respondents to the first and second reminder letters.
Adolescent↗
Investigating the proxy effect and the saliency principle in household based postal questionnaires.
STUDY OBJECTIVE: The aim was to investigate two possible sources of bias inherent in using a household based postal questionnaire, the "proxy effect", inaccurate reporting about characteristics of others, and the "saliency principle", reporting of only the most salient features. This is of importance in surveys concerned with screening the population to identify individuals with certain characteristics, and so possibly relying on one member of the household to reply on behalf of all others. DESIGN AND SETTING: A two stage survey of disablement in the population was undertaken. A first phase postal questionnaire was sent to 25,168 households in Calderdale, West Yorkshire, England, to ascertain the prevalence of physical disability and of troubles with the joints. The second phase comprised in depth interviews with a sample of individuals identified in the first phase as being disabled. RESPONDENTS: A total of 21,889 postal questionnaires were returned (87%) representing households containing 42,826 people aged 16 years and over. A disproportionately stratified random sample of 950 respondents reporting disability was taken in the second phase. Of these 891 were still available, and 838 (94%) were interviewed. MEASUREMENTS AND MAIN RESULTS: The postal questionnaire found that almost 29% of those who lived "alone" (without another adult) reported some level of disability, compared to only 10% of those who lived with others. The difference remained significant after standardisation. This apparent underreporting or "proxy effect" was present for reporting about disability overall, but not for severe disability (dependence on help of others), which suggests the operation of the "saliency principle". Reporting on joint troubles appeared to be affected by the proxy effect both for any joint problems, and when more than five joints were affected. Analysis of a small set of postal questionnaires from respondents who reported joint problems only at interview and where we could identify who had completed the postal questionnaire supports the hypothesis of a proxy effect; two thirds of the original postal questionnaires had been completed by a proxy. The results were further complicated by an interaction between reporting of disability and joint troubles: the greater the level of disability, the less likely the reporting of joint troubles. CONCLUSIONS: The findings have general implications for studies involving postal household screening questionnaires, and raises additional concerns about those that are multitopic in content. In surveys of symptoms and minor disability, a proxy effect is likely to be operative. This effect is not apparent for obvious and long standing problems such as dependence on others for help. However the interaction between the reporting of disability and joint symptoms carries important implications for the development of multitopic postal screening questionnaires.
Adolescent↗
Clinical evaluation of the rocker bottom crutch.
One hundred fifty hospitalized patients referred to a physical therapy department for crutch walking instruction were evaluated in a randomized, controlled crossover study with "rocker bottom" and conventional axillary crutches. A large training effect was observed with each crutch, but no significant differences (all P greater than .05) of gait speed, stride length, heart rate, stability, or feeling of security were noted between the groups. Thus, rocker bottom crutches, despite potential stability and energy conservation benefits, were found to be no more effective than conventional axillary crutches in this hospital setting.
Aged↗
Synthesis of research findings through meta-analysis.
Meta-analysis is an alternative, quantitative approach to the analysis and synthesis of multiple investigations of the same clinical question. The statistical approaches that have been developed since Glass coined the term meta-analysis in 1976 are discussed. Clinicians will find meta-analysis helpful when there are conflicting research findings about perplexing clinical problems.
Bias↗
The effects of cluster sampling in an African urban setting.
Cluster sampling was popularised by the sampling procedure promoted by the WHO/UNICEF for the evaluation of the expanded programme of immunisation (EPI). Without a clear understanding of the limitations of the sampling strategy used, this sampling strategy has been extended to other types of surveys. This article shows how to approach the assessment of cluster sampling techniques scientifically by calculating design effects (DEFFs) and rates of homogeneity (roh) and illustrates this scientific assessment with three case studies from Alexandra in South Africa. We report on the DEFFs and rohs for variables studied in these surveys. The DEFF for all the variables relating to housing tended to exceed two and was as high as 6.99 for the variable new development. The variables relating to health service utilisation and health practices, namely immunisation status, nutrition status, presence of Road to Health Cards (RTDCs), breast-feeding and knowledge of diarrhoea and oral rehydration all had a DEFF close to one. The variables relating to contraception use, literacy and schooling had DEFFs close to one and a half. For a few variables the DEFFs were below one and the rates of homogeneity less than zero. The highest values of roh were for environment factors (all above 0.1433). Rohs for factors related to utilization of PHC services were mostly between 0.0200 and 0.0499. No single class of factors seemed to be related to very low values of roh. These results are then discussed.
Cluster Analysis↗
Intervention studies in nursing: is the effect due to the independent variable?
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Clinical Protocols↗
[Attributable risk percent under an effect modifier and legal causality].
Among civil trials there are cases which are influenced by evidence derived from epidemiologic studies. In such cases, causality of a factor (X) illegitimately introduced by defendants is considered to be measured with an epidemiologic measure, attributable risk percent (AR%) expressing the level of risk. This paper aims to discuss calculations and interpretations of AR% in complicated cases where plaintiffs themselves introduced an additional risk factor (Y) for the alleged health injury. When X is not an effect modifier, AR% of X adjusted for Y can be simply adopted for arriving at a judgement of causality. Where Y is an effect modifier, and is not an indispensable item in the plaintiffs' daily life (e.g., smoking), the AR% of X for those not exposed to Y and also the AR% for those exposed to Y may both need to exceed a legally determined threshold, in order for X to be legally acknowledged as being causal to the alleged injury. The role of epidemiologists for such trials is to determine the AR% of X for each level of Y, and to advise the court on a realistic range of the AR%s.
Effect Modifier, Epidemiologic↗
Family-oriented prevention of cardiovascular disease: a social epidemiological approach.
A social epidemiological approach has been used to study social factors associated with chronic disease, as well as to promote community-oriented intervention programs to modify risk for cardiovascular disease. The present review suggests using a social epidemiological approach in a third way; to promote efforts directed toward family-oriented primary prevention of cardiovascular disease. Evidence is presented which shows an association between three family social factors (marital status, family socioeconomic status, family size) and risk for cardiovascular disease. The real determinants of risk, however, may be the underlying health-related behaviors indicated by each of these factors. Evidence is also presented which shows the importance of a fourth family social factor (family age) in promoting effective health education efforts to modify risk. Thus, a social epidemiological approach is more valuable than a single discipline-based approach in identifying, understanding, and modifying family social influences on cardiovascular risk.
Adult↗