Book Review. 1. Epidemiology, study design and data analysis (2nd edn). Mark Woodward, Chapman & Hall/CRC, Boca Raton, Building an up-to-date understanding of the methodologies that can be used to shape public health policies, Epidemiology: Study Design and Data Analysis. nd. Edition, Gerstman. Designing Clinical. Research. 3rd Edition, Hulley 2nd Edition, .. Epidemiologic methods plus clinical decision analysis and an bestthing.info bestthing.info
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Bayesian Data Analysis, Second Edition. Andrew Epidemiology—Study Design and Data Analysis Statistics in Research and Development, Second Edition. Epidemiology: Study Design and Data Analysis (2nd ed.). Request Full-text Paper PDF Design of Computer Experiments for Metamodel Generation. Article . International Standard Book Number (eBook - PDF) x EPIDEMIOLOGY: STUDY DESIGN AND DATA ANALYSIS, 3RD EDITION.
Many different study designs can advance a life course health-development framework. Although certain design strategies, namely, cohort studies, lend themselves more readily to the life course approach—examining the process of health development and its emphasis on emergent, person-context relations, and plasticity across the lifespan—we also describe other study designs that can be used to further our understanding of health and the development of different disorders and diseases from the life course perspective.
The benefits and limitations of alternative design approaches are discussed using one study question as an example—investigating the relationship between traumatic experience and the development of a substance use disorder. Theories underlying life course approaches are varied, but each emphasizes the importance of the occurrence and accrual of life events, plasticity, thriving, or risk over time and how these contribute to the development of particular outcomes of interest, including pathways associated with optimal health George ; Kuh et al.
A number of key questions pertinent to the emergence of health development across the lifespan can be addressed using life course frameworks that would otherwise be difficult to ascertain. From furthering our understanding of familial and genetic contributions to the aetiology of health conditions to exploring the natural course of disorders in different populations and to examining the time-specific and cumulative impacts of social and environmental factors, the use of a life course framework has advanced our understanding of the systemic causes and course of multiple health conditions and positive health development.
The goal of the field of epidemiology is to advance the understanding of the determinants of health and disease among human populations. These developments in epidemiology were influenced by earlier and parallel advances in the field of human development c. In epidemiology, as in other disciplines, we have come to understand that few, if any, events occur in isolation Barker ; Elder and Shanahan Hence, the central focus in life course approaches to health development and life course epidemiology is on the complex process of occurrence and accrual of risks at multiple levels.
For example, the probability that two identical twin infants will develop a substance use disorder may differ due to a number of subtle environmental differences that each encounters over the course of their life. Epidemiological research shares basic goals with life course development concerning the origins, course, and prevention of health, disease, and disorder and, in turn, through the integration of the perspectives, the promotion of health development.
Both advance through a variety of traditional and more recently developed study designs Aschengrau and Seage ; Rothman et al. Each study design represents a different approach to common research questions and has implications for the ways in which study participants are selected and information is collected and analysed. The design chosen by an investigator is driven by the research question being posed along with considerations of cost, efficiency, and ethical and practical considerations Aschengrau and Seage ; Woodward While many traditional epidemiological questions can be addressed through a number of alternative designs, some are of limited utility for issues at the core of a life course health development approach.
The organization is by study design and describes major features of each design approach, key instances of each design, and potential challenges and limitations associated with each design. To limit the scope of this chapter, we take as an example the study of substance use and substance use disorder diagnosis as an instance of a complex health condition warranting investigation from a life course perspective.
Although certain design strategies, namely, cohort studies, lend themselves more readily to the life course approach, we have chosen to describe other study designs that can also be used to further our understanding of health, disorder, and disease from the life course perspective.
[PDF] Epidemiology: Study Design and Data Analysis, Third Edition Download Online
The chapter concludes with general considerations for designing life course studies, as well as recommendations for future directions of the field. One frequent topic in life course epidemiology is the initiation, progression, and trajectories following substance use.
Given the emphasis in the LCHD principles of the role of synchrony in the timing of developmental processes at multiple levels, ranging from the molecular through the historical evolutionary , a life course approach has been useful in assessing the timing of substance use onset, the broader contexts that contribute to early use patterns, the progression from use to abuse or dependence, and the identification of intergenerational and early life experiences on substance use patterns Magnusson ; Jablonka and Lamb One particular research question that has been examined extensively is the relationship between traumatic experience and the development of a substance use disorder.
Over the past century, this question has been examined using a variety of different study designs in an effort to more thoroughly probe the potential causal link between trauma and the aetiology of substance use disorder.
As the chapter progresses, we use this topic to illustrate the ways in which various threats to the validity of a claim for causality manifest under different study designs.
For the purposes of a clear illustration, we focus on diagnosed substance use disorder as our outcome. As compared with experimental studies, in which exposures are randomly assigned to study participants, in observational designs, the investigator observes and records data on a group of people, with no active manipulation of exposure conditions, generating information on the relationships between exposure and disease as they naturally unfold.
Whereas the causal inferences that can be derived from observational studies are typically not as strong as those in experimental studies, observational studies are free from the ethical dilemmas associated with allocating exposure in experimental designs.
Observational studies typically take two forms, cohort studies or case—control studies; each form has a number of variations. This is one of the preferred design options for studying substance use disorders across the life course because it allows for direct measurement of both exposures and outcomes as they occur, providing strong evidence for temporality of exposure—outcome relationships.
These designs are also useful for illustrating the importance of the LCHD principle regarding the importance of the timing and social structure of exposure to environmental events, both normative and non-normative Baltes et al. There remain, however, many important design considerations, challenges, and limitations in the design and conduct of such studies.
In a cohort study, participants are often selected to be representative of a larger population of interest—defining the relevant population of interest is central to designing a maximally informative cohort study.
In some instances, the population may be defined by the set of key exposures of interest—e. In others, the most informative population may be those at elevated risk of developing disease, e. If an investigator has multiple outcomes of interest, it can be difficult to identify specific subpopulations at risk of disease, in which case a more general population may be most appropriate.
Data are collected to provide information on the outcomes that are the focus for the study; the implications for this are particularly important in a prospective study because, as the cohort ages, an investigator may wish that additional data had been collected on another exposure or disease Susser et al.
Additionally, decisions related to study design and data collection are made relative to the science of the field when the study is initiated. This phenomenon is referred to as the scientific period effect Susser et al. Illustrating and reflecting how health development research is embedded in historically defined scientific periods, it has become a truism that many of the greatest discoveries of long-term prospective cohort studies were not anticipated at the time of initiation and that certain data such as genetic material that become relevant at a later scientific time may have been overlooked at the onset of earlier projects.
Another key consideration in designing a prospective cohort study is minimizing study dropout and loss to follow-up. Given the long periods of follow-up often involved in prospective cohort studies, it is especially important to consider procedures to minimize study dropout during the planning phase. A number of strategies have been used to minimize study attrition: collection of detailed contact information, sending reminders of follow-up interviews, building rapport, and sharing study findings with participants in the form of newsletters or bulletins Wadsworth et al.
Challenges and Limitations of Cohort Studies Cohort studies have contributed greatly to our understanding of the prevalence and distribution of substance use disorders, the course of disorders across time, and information related to utilization of substance use treatment services. They have also been useful in illustrating a number of the challenges and limitations associated with carrying out a long-term prospective cohort study.
Considerable human and fiscal resources are needed to enrol, track, and retain participants and to carry out meaningful follow-up for such a long span of time.
These challenges are especially prominent in life course studies on substance abuse, due to the time and effort needed to accurately assess outcomes and the multiple potential contributing risk and protective factors that operate at varied levels of influence from molecular to societal on the initiation and progression of substance abuse. In addition, as in all observational studies, the designers of cohort studies must anticipate concerns about both imprecisely measured and unmeasured confounding which can undermine the utility of such efforts.
Faced with limited resources, investigators must balance the breadth, depth, and size of such cohorts: breadth in terms of the range of contributing conditions and potential confounders assessed, depth regarding the length and intensity of assessment, and size in terms of the number of participants enrolled. Informative cohort studies have ranged from hundreds to hundreds of thousands of participants with commensurate trade-offs between statistical power, on the one hand, and richness of data regarding the multiple complex developmental trajectories that may eventually manifest as disorder, on the other.
Finite resources demand additional trade-offs between cohort enrolment and retention. Successful cohort studies not only need a rich array of data regarding potential risk factors and outcomes, but meaningful inference also requires a high level of retention and protection against threats to validity resulting from attrition and resulting selection bias.
While some attrition is inevitable, considerable creative effort and investment in subject retention is necessary to ensure that costly cohort studies yield data of maximal scientific utility. While this applies for cohort studies in general, the close relationship between many disorders and social engagement such as participation in a prospective cohort study poses a particularly serious challenge for life course studies.
The extent to which attrition is also associated with risk conditions of interest may irrevocably reduce the potential of cohort studies to generate unbiased estimates of interest.
Despite these challenges, however, cohort studies will remain at the forefront of design options to advance the understanding of health development.
The strength of a cohort in the LCHD context is primarily the ability to investigate prospectively the synergistic influences of multiple conditions e. They are clearly the method of choice to examine the impact of potentially adverse or risk conditions, which could not be manipulated through a randomized design, due to ethical considerations.
Major Prospective Cohort Studies of Substance Use Disorder There are several important and well-known general prospective cohort studies examining substance use disorders across the life course.
Due to space limitations, we summarize the considerations and decisions made for two of these study designs: Woodlawn Study and Monitoring the Future Study These studies serve as excellent examples of the unique type of question that can be answered, as well as the challenges that arise in conducting a prospective cohort study for life course health development. Both studies employed a multi-wave prospective cohort design, and the Monitoring the Future study was designed to enroll a nationally representative sample of the American young adult population.
The Woodlawn Study, funded by the National Institute on Drug Abuse NIDA and initiated in , recruited a high-risk community of African-American first graders from the same disadvantaged inner city community in Chicago to examine risk factors for substance use disorder.
These first graders were followed for a total of four waves: first grade, adolescence, young adulthood, and midlife. This study collected data over the life course—from childhood through adulthood—and initiated data collection prior to the onset of drug use.
F.R.E.E [D.O.W.N.L.O.A.D] Epidemiology: Study Design and Data Analysis, Second Edition (Chapman
This design approach allows investigators to compare the onset of substance use disorder and substance use trajectories among children who had similar early roots but disparate pathways to adulthood in terms of family relationships, school, work, peer relationships, religion, and community involvement—a very useful design for a life course health development approach The Woodlawn Project: A Life Course Study Monitoring the Future MTF project, also funded by NIDA , began in using a multistage, stratified random sampling framework to enroll a cohort of participants that were representative of American high school students; each year about 16, students in approximately public and private high schools nationwide participate.
Though many use this dataset as panel data, or annual cohorts of nationally representative data, there is potential to use MTF as a prospective cohort study. Beginning with the class of , a randomly selected sample from each senior class has been followed up biannually after high school on a continuing basis. Twelve years past high school, participants receive their last young adult questionnaire and then follow-up procedures change to 5-year intervals to cover middle adulthood.
Both of these cohorts span multiple decades and multiple life stages, providing detailed information on trends in substance use disorder over the life course. They found that participants who had a traumatic event had more than a fourfold increase in risk of drug abuse or dependence compared with those with no history of a traumatic event, after controlling for a number of potential confounders. This study exemplifies the value of prospective cohort studies to advance causal inference in the absence of experimentation: it clearly establishes temporality of exposure traumatic event and outcome drug abuse or dependence , it uses a valid measure to identify diagnoses of drug abuse or dependence DSM-III-R diagnoses , and it takes into account a number of important factors that could potentially confound the true association between trauma and drug abuse or dependence.
Typically, selection bias is one of the greatest threats to the validity of an observational study. In this case, however, study participants were randomly selected from the membership list of a , member health maintenance organization in Southeast Michigan. Given all participants were likely from the same region, conclusions may not be generalizable to those in different parts of the country.
Thus, conclusions should be replicated elsewhere. Information bias is reduced in this example, as diagnoses of drug abuse or dependence were generated independent of knowledge of experiencing trauma. Finally, there remains the potential that there is residual and unmeasured confounding. In any study with such a wide scope and with multiple years of follow-up, there is always the possibility that an important potential confounder was overlooked or was not adequately measured.
Prospective cohort studies can span decades, which is very useful for a life course approach, but this comes with additional challenge. Parents are the primary target for recruitment, and, depending on the length of follow-up, parents may serve as the primary respondent even though the cohort of interest comprises the offspring generation. In a perinatal cohort study, the emphasis is on factors that occur in the months immediately prior to and following birth.
Therefore, studies of this design typically will recruit and enroll parents usually mothers who are pregnant or planning to become pregnant in the near future. Data are typically collected on the mother and child throughout the pregnancy , at birth, and for a defined length of time following birth.
In a birth cohort, investigators typically design a sampling scheme to target births that occur in a specific geographic region within a specified period of time. For both perinatal and birth cohorts, the length of follow-up is determined by the research questions being posed and the resources available for the study.
Issues related to data collection are another unique concern for perinatal and birth cohorts. Special consideration, however, must be given to the length and appropriateness of data collection procedures, training of interviewers, and study consent and assent procedures to ensure adequate protection of human subjects.
Over the years, birth and perinatal cohorts have proved an invaluable source of information in the study of life course health development. Benefiting from the general strengths of cohort studies e. This study design enables investigators to examine the impact of the foetal, infant, and early childhood experience on health development across the life course. We now describe two influential perinatal and birth cohorts, again limiting our scope to studies that have generated substance use disorder diagnoses.
Major Birth Cohort Studies of Substance Use Disorder There are several important birth cohorts that allow for the study of life course health development and assess substance use disorders.
The CPP is, in fact, not a birth cohort but rather a prenatal cohort. Across the United States, 12 university-affiliated medical centres participated, including two in New England in Boston and Providence. Data from examinations and interviews were recorded by trained staff at each site beginning at the time of registration for prenatal care, using standardized protocols, forms, manuals, and codes. At the first prenatal visit, a complete reproductive and gynaecological history, recent and past medical history, socio-economic interview, and family history were recorded.
Blood samples were collected for serology and for storage of frozen sera. After admission for delivery, trained observers recorded the events of labour and delivery, and the obstetrician completed labour and delivery protocols.
Diagnostic summaries were prepared by study physicians following the month and 7-year assessments. In recent years, this team has extended the follow-up and assessment of three-generation pedigrees in the NEFS, which is still ongoing i.
These projects all seek to integrate family designs with early life risk conditions, capitalizing upon the large number of cohort members with multiple offspring. A prominent birth cohort that measures substance use disorder and has taken a life course health development approach is the Dunedin Multidisciplinary Health and Development Study DMHDS. At each assessment, study members participated in physical tests, dental examinations, blood tests, and completed computer questionnaires and surveys.
Investigators attribute this low attrition rate to aggressive retention measures such as flying participants who had moved away back to New Zealand and using interviewers in other locations such as Australia Silva and Stanton Birth cohorts such as the CPP and the DMHDS are incredibly useful for life course health development research because they allow investigators to gain knowledge of developmental processes, as well as multilevel genetic and environmental risk factors.
Exposure information was collected from pregnant women at their first prenatal visit, and these questions were repeated at each subsequent prenatal visit up until the time of delivery.
First, the sample of this particular birth cohort is not representative of a broader population, and therefore external validity is potentially limited. Also, given the long period of follow-up, obstetric care at birth was very different than the modern level of care.
Specifically, the mortality rate for those born prematurely was much higher in the late s—thus many children suffering from behavioural regulation problems and poor academic functioning may be offered more effective assistance had they been born today. Finally, as with all observational study designs and those with long follow-up periods, there remains the potential that there is residual and unmeasured confounding.
Using twins as study participants helps investigators advance understanding of genetic and environmental risks, differentiate between genetic influences in different subgroups of people e.
Ultimately, twin studies allow researchers to estimate the proportion of variance in a trait attributable to genetic variation versus the proportion that is due to shared environment or unshared environment Bundey Twins are usually recruited from registries, which now exist across the globe.
Twin studies can be conducted across study design types, thought the most robust would be longitudinal—similar to a prospective cohort design Boomsma et al. There are several important considerations in twin studies. First, studying twins who grow up in a shared environment does not allow the researcher to consider the effects of both shared environment and gene—environment interaction simultaneously.
Rather, this can be addressed by including additional non-twin siblings in the design. Second, results from twin studies cannot be directly generalized to a broader population as there may be genetic factors that lead specifically to a higher incidence of twinning.
This raises potential threats to external validity Bundey Traditionally, the general consensus was that twin studies represented an optimal study design to examine gene—environment interactions across the life course. This criticism may be unduly harsh as 1 with human populations, observation rather than experimental manipulation of gene—environment interactions is the only ethical option and 2 contemporary behavioural geneticists typically avoid simplistic black-box approaches, with hypotheses and analyses informed by other biological and developmental sciences.
Recent developments in high-dimensional analysis of both genetic e. GWAS and environmental EWAS factors may help advance traditional approaches to understand the interactive influences of genetic and environmental influences on life course health development Patel et al.
Major Twin Studies of Substance Use Disorder There are many twin registries and twin studies around the world, most of which are in Europe. A few of these have been used to examine substance abuse, two of which we will highlight: the Danish Twin Registry and the Swedish Twin Registry.
The Danish Twin Registry was established in the s and is one of the oldest twin registries in the world. The registry now comprises information on almost all twins born in Denmark since It contains data from church books, the Central Office of Civil Registration, health behaviour and lifestyle variables, and clinical examinations for more than 88, twin pairs Skytthe et al. Though substance use disorder is one of many outcomes assessed in the registry data, hundreds of other studies using this registry have examined ageing, age-related health, cardiovascular disease, and other rare diseases Boomsma et al.
The Swedish Twin Registry contains three cohorts, each differing by ascertainment and extent of data collection. The first cohort was born between and Data for the first cohort was ascertained from all parishes across Sweden and contains information on demographics, risk behaviours, cardiovascular health, respiratory health, and environmental exposures.
Information on the second cohort, born between and , was ascertained using nationalized birth registrations and mailed questionnaires. Information covered similar domains as the first cohort and also collected an additional personality inventory. The third cohort, born between and , was identified by birth registry and has been linked to the Medical Birth Registry.
Researchers working with the Swedish Twin Registry have now begun an effort called Screening Across the Lifespan Twin SALT study in which investigators have identified subsamples of twins in the registry for more in-depth studies in which blood samples will be obtained; phenotyping and genotyping will be performed; detailed information on health behaviours, clinical diagnoses, and medications will be collected; and linkages will be made to medical records Lichtenstein et al.
Both of these registries, as well as twin cohorts generally, pose a unique opportunity to examine the multilevel and multidimensional genetic and environmental risks for health development across the life course.
Twin Cohort Example: Childhood Sexual Abuse and Substance Use Disorder The research literature has consistently suggested a link between childhood sexual abuse and negative health outcomes, but there remain concerns for selection bias and confounding by family environment.
To address this question while minimizing confounding by family environment, investigators derived a sample of female—female twin pairs and male—male twin pairs from a young adult Australian volunteer twin panel. Structured psychiatric telephone interviews were conducted to assess childhood sexual abuse and adverse psychosocial outcomes including alcohol dependence DSM-IV and nicotine dependence DSM-IV. Family background information was elicited including parental fighting, parental conflict, stepparent presence, neglect, and physical abuse.
Results suggested that individuals with a history of childhood sexual abuse have increased risk of developing alcohol and nicotine dependence. Results also showed that childhood sexual abuse is associated with substantial risk that is not explained by other family background factors. There is, however, a potential for bias. Selection bias may have arisen due to the fact that parents aware of abuse may have been less likely to volunteer their twins for research.
Regardless, using a twin study approach allowed researchers to dissect the direct and correlated family background effects of childhood sexual abuse Nelson et al. Often, subjects are identified as being at high risk for developing the outcome of interest based on particular behaviours and characteristics or manifestations of previous pathology in their parents.
Studies such as these allow researchers to better examine the natural history of disorders in relation to a particular high-risk population.
One potential limitation of high-risk studies, however, is that their results, and, ultimately, the conclusions they draw, may only be applicable for high-risk populations. SlideShare Explore Search You. Submit Search. Successfully reported this slideshow.
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Given all participants were likely from the same region, conclusions may not be generalizable to those in different parts of the country.
We might argue that these children have come into contact with dog faeces and thus contracted toxoplasmosis. WoldeabWoldemariam I can not download the book please assist me. An association is still present here: For the second with the outlier. Yet, there is the potential for selection bias insofar as the comparison group may not be representative of the population from which the cases arose; for instance, there may be something systematically different between those with a history of childhood sexual abuse and those in the general population.
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