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PubMed1987

An introduction to the use of epidemiologic research methods in dairy science.

Many dairy scientists are not familiar with epidemiologic study designs and measures. The various designs (cross-sectional, case-control, cohort) are reviewed with special reference to their strengths and weaknesses. Epidemiologic measures (incidence and prevalence rates, relative risk, odds ratio, attributable fraction, and population attributable fraction) are defined, and their validity in the contexts of the different study designs is discussed. Incidence rate (risk of disease) is the number of new cases of a disease divided by the population at risk during a specified time period. Prevalence rate is the frequency of both new and old cases in a population at a specified point or period in time divided by the average population during that same period. Both incidence and duration of disease contribute to prevalence. Odds ratios and relative risks are measures of association (how much disease the exposed group experienced relative to the nonexposed group) and are used to assess the relative importance of risk factors. Attributable fraction is the proportion of the incidence in the exposed group that can be attributed to the specific exposure. Population attributuable fraction is the expected reduction in incidence in the whole population if the specific exposure were prevented. The attributable fractions are useful in planning preventive and herd health programs.

Animals↗
PubMed1984

A comparison of frequency and quantitative dietary methods for epidemiologic studies of diet and disease.

Agreement between frequency and quantitative dietary methods was assessed for the ability of frequency intake data to substitute for quantitative intake data in diet-disease investigations. Frequency and quantitative intakes of 342 male subjects participating in an ongoing case-control study in Hawaii during 1981-1982 were obtained using a recall interview method designed to assess usual dietary habits. The extent of agreement between frequency and quantitative intakes of various dietary components (44 food items, 20 food groups, 8 nutrients) was determined at the group and individual subject levels, and with regard to specific study objectives. The results showed that for studies based on aggregate data, frequency and quantitative dietary methods will give reasonably comparable results in analyses involving food items. However, for similar studies involving food groups and nutrients, and for all studies based on individual data, frequency dietary methods cannot be relied on to yield the same diet-disease associations as would corresponding quantitative methods.

Diet↗
PubMed2002

Observational methods in epidemiologic assessment of vaccine effectiveness.

Observational methods are important in the measurement of vaccine effectiveness (VE) as experimental designs cannot be used for measurement of vaccines already on the vaccination schedule. Furthermore, efficacy measured in clinical trials under ideal conditions may differ to effectiveness in the field under non-ideal conditions and in different populations. In addition to post-licensure surveillance, observational VE studies are particularly important when disease incidence does not predictably decrease with increased vaccine coverage, when high proportions of vaccine failure among reported cases suggest a problem with the vaccine or when issues arise that were not predicted in pre-licensure evaluations. Commonly used study types for evaluating VE include cohort studies, household contact studies, case-control studies, the screening method and case-cohort studies. There are many potential biases in all observational VE studies which should be considered in the study design and analysis stage. Of the five observational study types reviewed, cohort studies undertaken during an outbreak investigation offer the simplest means of VE estimation and is the preferred study design where the situation permits. Where this is not possible the screening method is the most economical and rapid method. It is essential that the effectiveness of all vaccination programs be evaluated. As new vaccines are introduced to the schedule, booster doses are added and the timing of doses changed, the role of observational methods in the evaluation of VE will become even more important. To date, few observational VE studies have been undertaken in Australia, suggesting the under-utilisation of these methods.

Case-Control Studies↗
PubMed2001

Local television news coverage of traumatic deaths and injuries.

OBJECTIVE: To assess how local television news programs' reporting of injuries and deaths from traumatic causes compares with coroners' records of deaths and the estimated incidence of injuries in the same geographic area during the same time. METHODS: Using epidemiologic methods, we identified the underlying cause of death or injury in each of 828 local television news stories broadcast in Los Angeles during late 1996 or early 1997 that concerned recent (<3 days) traumatic injuries or deaths in Los Angeles County. Odds ratios were computed using deaths by homicide or injuries sustained in assaults as the referent group. RESULTS: The number of persons depicted as dead amounted to 47.8% of the actual total number of traumatic deaths occurring in Los Angeles County during the study period. In contrast, the number depicted as injured represented only 3.4% of injuries due to traumatic causes. Both injuries and deaths due to fires, homicides, and legal interventions were proportionally well represented. However, injuries and deaths from accidental poisoning, falls, and suicide were significantly underrepresented. CONCLUSIONS: Some types of events receive disproportionately more news coverage than others. Local television news tends strongly to present only those events concerned with death or injury that are visually compelling. We discuss reasons for concern about the effect that this form of information bias has on public understanding of health issues and possible counteractions that physicians can take.

Cause of Death↗
PubMed2005

Ionizing radiation and chronic lymphocytic leukemia.

The U.S. government recently implemented rules for awarding compensation to individuals with cancer who were exposed to ionizing radiation while working in the nuclear weapons complex. Under these rules, chronic lymphocytic leukemia (CLL) is considered to be a nonradiogenic form of cancer. In other words, workers who develop CLL automatically have their compensation claim rejected because the compensation rules hold that the risk of radiation-induced CLL is zero. In this article we review molecular, clinical, and epidemiologic evidence regarding the radiogenicity of CLL. We note that current understanding of radiation-induced tumorigenesis and the etiology of lymphatic neoplasia provides a strong mechanistic basis for expecting that ionizing radiation exposure increases CLL risk. The clinical characteristics of CLL, including prolonged latency and morbidity periods and a low case fatality rate, make it relatively difficult to evaluate associations between ionizing radiation and CLL risk via epidemiologic methods. The epidemiologic evidence of association between external exposure to ionizing radiation and CLL is weak. However, epidemiologic findings are consistent with a hypothesis of elevated CLL mortality risk after a latency and morbidity period that spans several decades. Our findings in this review suggest that there is not a persuasive basis for the conclusion that CLL is a nonradiogenic form of cancer.

Eligibility Determination↗
PubMed2006

[Additional cardiovascular risk factors associated with excess weight in children and adolescents: the Belo Horizonte heart study].

OBJECTIVE: To examine the association of overweight and obesity with physical activity, blood pressure (BP) and serum lipid profiles. METHODS: Epidemiologic investigation of 1,450 students, between the ages of 6 and 18, in the city of Belo Horizonte, MG. DATA: weight, height, BP, skinfold thickness, waist circumference, physical activity, total cholesterol (TC), LDL-c, HDL-c, and dietary habits. RESULTS: The prevalence rates for overweight and obesity were 8.4% and 3.1%, respectively. In relation to the students in the lower quartile (Q1) of the distribution of subscapular skinfold, the students in the upper quartile (Q4) presented a 3.7 times higher risk (odds ratio) of having elevated TC levels. Overweight and obese students had a 3.6 times higher risk of having elevated systolic blood pressure, and a 2.7 times higher risk of elevated diastolic blood pressure when compared to normal weight students. The less active students in the Q1 of distribution of MET presented a 3.8 times higher risk of having elevated TC levels compared to those who were more active (Q4). CONCLUSION: Students who were overweight, obese or in the upper quartiles for other adiposity variables, as well as students with low levels of physical activity or a sedentary lifestyle presented higher blood pressure levels and a lipid profile indicative of an increased risk of developing atherosclerosis.

Adolescent↗
PubMedDate not supplied

Estimated economic costs of obesity to U.S. business.

OBJECTIVE: To estimate the economic costs of obesity to U.S. business. METHODS: Standard epidemiologic methods for risk attribution and techniques for ascertaining cost of illness were used to estimate obesity-attributable expenditures on selected employee benefits, including health, life, and disability insurance and paid sick leave by private-sector firms in the U.S. in 1994. Data were obtained from a variety of secondary sources, including the National Health Interview Survey, reports from the Bureau of Labor Statistics and other federal agencies, and the published literature. Attention was focused on employees between the ages of 25 and 64 years who were classified according to body mass index (BMI) as "nonobese" (BMI < 25 kg/m2), "mildly obese" (BMI = 25-28.9 kg/m2), or "moderately to severely obese" (BMI > or = 29 kg/m2). RESULTS: The cost of obesity to U.S. business in 1994 was estimated to total $12.7 billion, including $2.6 billion as a result of mild obesity and $10.1 billion due to moderate to severe obesity. Health insurance expenditures constituted $7.7 billion of the total amount, representing 43% of all spending by U.S. business on coronary heart disease, hypertension, type 2 diabetes, hypercholesterolemia, stroke, gallbladder disease, osteoarthritis of the knee, and endometrial cancer. Obesity-attributable business expenditures on paid sick leave, life insurance, and disability insurance amounted to $2.4 billion, $1.8 billion, and $800 million, respectively. CONCLUSIONS: The health-related economic cost of obesity to U.S. business is substantial, representing approximately 5% of total medical care costs. Further research is needed to determine the cost-effectiveness of worksite weight management programs and of other efforts to reduce the prevalence of obesity in the U.S. workforce.

Adult↗
PubMed2002

An outbreak of Legionnaires' disease in an inner city district: importance of the first 24 hours in the investigation.

OBJECTIVE: To present the main results of the investigation of an outbreak of Legionnaire's disease that occurred in an inner city district of Barcelona between 15 October and 15 November 2000. METHODS: Epidemiological surveys of patients and environmental investigations were initiated on the day the first five cases were notified. Water samples and smears from cooling tower trays were taken for microbiological analysis. Maps of the distribution of cases and possible contamination foci were elaborated. Incidences were calculated for each census tract. RESULTS: A total of 54 patients related to the outbreak were identified, with a case fatality rate of 5.5%. Incidence rate in the area closest to the cooling tower (6.40/1000) was significantly higher than that of the rest of the neighbourhood (2.23/1.000, RR 2.87, 95%CI 1.37-6.12, P = 0.0035). Cultures positive for Legionella pneumophila serogroup 1, subtypes Pontiac, Philadelphia or Allentown, were obtained from eight patients. On the 39th day of the investigation it was found that the strain isolated in one of the cooling towers coincided with the serogroup, subtype and molecular profiles identified in clinical samples. CONCLUSIONS: Rapid coordination of clinicians, microbiologists, epidemiologists and environmentalists permitted the source of infection and the affected cases to be correlated within a few days.

Adult↗
PubMed2004

[Comparative investigation of the Rh blood type distribution between the Uygur and Han nationalities in the Khotan area of Xinjiang Autonomous Region].

OBJECTIVE: To investigate the Rh blood type distribution in the Uygur and Han nationalities in Khotan area of Xinjiang Autonomous Region, China, and compare the results with previous documentations on the Rh blood type in Uighurs. METHOD: Using epidemiological methods, an extensive survey was conducted for determination of the Rh blood type in 2,907 residents in the target area, including 2,251 Uighurs and 656 subjects of Han nationality. Positive definition method was used for the ABO blood typing while Rh blood type was determined serologically through saline medium method. At the same time, the Rh phenotypes were investigated in RhD-negative individuals. RESULTS: Altogether 106 RhD-negative individuals were identified, accounting for a rate of 4.71% in this cohort, with the D gene frequency of 0.217. The Rh phenotype of all RhD-negative cases were ccdee except for one that was ccdEe. When compared with the previous ABO blood type distribution data of the Uighurs in randomly chosen samples, B type in RhD-negative individuals was relatively higher while A and O types peared lower. CONCLUSION: The Rh blood type frequency is relatively higher in the Uighurs with unique Rh phenotypes.

ABO Blood-Group System↗
PubMed1987

Preventive strategies in sexually transmitted diseases for the primary care physician. US Preventive Services Task Force.

This study provides the background recommendations of the US Preventive Services Task Force for interventions by primary care physicians to prevent sexually transmitted diseases. Rationale for and data supporting use of barrier methods, epidemiologic treatment, contact tracing, patient education, prophylactic antibiotics, and disease reporting are discussed. Specific recommendations include those for gonorrhea, syphilis, human immunodeficiency virus infection, enteric infections, human papillomavirus infection, herpes simplex virus infection, and Chlamydia trachomatis infection.

Acquired Immunodeficiency Syndrome↗
PubMed1995

[Investigation of an outbreak of water-borne typhoid fever in Catalonia in 1994].

BACKGROUND: Typhoid fever incidence in Spain, and particularly in Catalonia has decreased significantly since 1985. Water borne outbreaks can affect large numbers of people. These two reasons make specially interesting to study all suspected typhoid fever outbreaks, like the one that happened in March 1994 in Bages county (Barcelona). METHODS: Epidemiological questionnaires were conducted to investigate the origin of the outbreak, the presence of related cases in the same area, and the household contacts of cases S. typhi isolates were characterized by serotyping, biotyping, phage-typing, ribotyping and pulsed field gel electrophoresis analysis of DNA. RESULTS: Nine cases were identified. All cases were treated with antibiotics, with clinical success. There were not secondary cases. The possible origin was a drinking fountain. All the strains had the same epidemiological marker patterns. CONCLUSIONS: Breaking of the sewer pipes near to the drinking fountain was probably the origin of the contamination. It can be concluded the importance of keeping a good epidemiological control system to investigate and prevent outbreaks. It is also important to control the drinking fountains to prevent its contamination. Finally it is necessary to highlight the utility of epidemiological markers to fully characterized the involved strains.

Adolescent↗
PubMed2003

Validation methodology in publications describing epidemiological registration methods of dental caries: a systematic review.

OBJECTIVE: The aim was to describe and systematically review the methodology and reporting of validation in publications describing epidemiological registration methods for dental caries. BASIC RESEARCH METHODOLOGY: Literature searches were conducted in six scientific databases. All publications fulfilling the predetermined inclusion criteria were assessed for methodology and reporting of validation using a checklist including items described previously as well as new items. The frequency of endorsement of the assessed items was analysed. Moreover, the type and strength of evidence, was evaluated. MAIN OUTCOME MEASURES: Reporting of predetermined items relating to methodology of validation and the frequency of endorsement of the assessed items were of primary interest. RESULTS: Initially 588 publications were located. 74 eligible publications were obtained, 23 of which fulfilled the inclusion criteria and remained throughout the analyses. A majority of the studies reported the methodology of validation. The reported methodology of validation was generally inadequate, according to the recommendations of evidence-based medicine. The frequencies of reporting the assessed items (frequencies of endorsement) ranged from four to 84 per cent. A majority of the publications contributed to a low strength of evidence. CONCLUSION: There seems to be a need to improve the methodology and the reporting of validation in publications describing professionally registered caries epidemiology. Four of the items assessed in this study are potentially discriminative for quality assessments of reported validation.

Dental Caries↗
PubMedDate not supplied

[New method of epidemiological surveillance of influenza mortality in the USA].

This paper describes a new method of forecasting the expected number of pneumonia and influenza (P and I) deaths on the basis of time-series analysis of historical mortality data. The new method is different in three aspects from the regression method developed by Serfling and used by the Centres for Disease Control (CDC) since 1963 in that it uses the ratio of P and I deaths to deaths from all causes in lieu of the total number of P and I deaths in forecasting the expected numbers. Also, instead of deleting epidemic periods in the forecast, these weeks are replaced by expected numbers. Finally, forecasting is done with a time-series model instead of the regression model.

Adolescent↗
PubMed1959

Epidemiology in the social sciences.

The techniques and principles of epidemiology, so successfully utilized in the study and control of communicable diseases, should be applied to other mass phenomena in the community. The local health officer should apply them in his "diagnosis" of the sicknesses of his organized community. Epidemiological methods have been used to study mental diseases as well as chronic diseases, and an experiment in using epidemiological methods on the county level to study psychosocial disorders has been carried out. The impact of psychosocial episodes on somatic diseases is now generally accepted and well documented. Individual practitioners of medicine are becoming more interested in the significance of social tensions on the health of their patients. Public health physicians, specialists in preventive medicine, are the best equipped by training and experience to take the leadership in the application of epidemiological methods to sociomedical problems and are in a unique position to assist their colleagues in the private practice of medicine in providing modern helpful and meaningful health protection to their patients.Organized medicine might well become more cognizant of the sociological changes taking place in the nation as they relate to health and assume the responsibility for aggressive leadership in the anticipation of and the solution of these problems.

Epidemiologic Methods↗
PubMed2006

Match rate and positional accuracy of two geocoding methods for epidemiologic research.

PURPOSE: This study compares the match rate and positional accuracy of two geocoding methods: the popular geocoding tool in ArcGIS 9.1 and the Centrus GeoCoder for ArcGIS. METHODS: We first geocoded 11,016 Texas addresses in a case-control study using both methods and obtained the match rate of each method. We then randomly selected 200 addresses from those geocoded by using both methods and obtained geographic coordinates of the 200 addresses by using a global positioning system (GPS) device. Of the 200 addresses, 110 were case maternal residence addresses and 90 were control maternal residence addresses. These GPS-surveyed coordinates were used as the "true" coordinates to calculate positional errors of geocoded locations. We used Wilcoxon signed rank test to evaluate whether differences in positional errors from the two methods were statistically significantly different from zero. In addition, we calculated the sensitivity and specificity of the two methods for classifying maternal addresses within 1500 m of toxic release inventory facilities when distance is used as a proxy of exposure. RESULTS: The match rate of the Centrus GeoCoder was more than 10% greater than that of the geocoding tool in ArcGIS 9.1. Positional errors with the Centrus GeoCoder were less than those of the geocoding tool in ArcGIS 9.1, and this difference was statistically significant. Sensitivity and specificity of the two methods are similar. CONCLUSIONS: Centrus GeoCoder for ArcGIS for geocoding gives greater match rates than the geocoding tool in ArcGIS 9.1. Although the Centrus GeoCoder has better positional accuracy, both methods give similar results in classifying maternal addresses within 1500 m of toxic release inventory facilities when distance is used as a proxy of exposure.

Databases as Topic↗
PubMed1996

Capture-recapture methods in epidemiological studies.

Medical researchers often are faced with the challenge of estimating the total number of cases in a population based on incomplete samples. Because of a lack of explicit methods for determining if all cases have been counted, indirect methods for estimating the abundance of disease have been developed. Capture-recapture models are an indirect method of estimating population sizes that have been employed in recent epidemiological studies. These methods, derived from techniques developed for studies of animal abundance, estimate the true population size by evaluating the degree of overlap among incomplete lists of cases from existing data sources. Although intuitively appealing, the successful application of these methods is dependent upon a clear understanding of the biology of the disorder involved, the dynamics of the reference population, and the assumption and robustness of the specific models used. Failure to address these issues can lead to inaccurate and sometimes misleading results. This article describes some of the strengths and limitations of recapture techniques and provides the reader with a foundation from which to explore the methods in further detail.

Animals↗