Epidemiology of Asthma
Jonathan A. Bernstein, Mark L. Levy in Clinical Asthma, 2014
The prospective cohort study design follows groups of individuals who may not have manifested a disease or an outcome at the time of recruitment; it is often used to identify significant host and environmental influences on health and environmental exposures, and their effects on the expression of chronic disease later in life.14 Large numbers are, however, typically required in order to identify significant differences in the incidence in exposed and nonexposed groups. This requirement for large numbers of cases usually means that cohort studies are expensive to establish and maintain. Genome-wide association studies (GWAS), whereby large cohorts of patients are recruited to detect novel genes and markers associated with disease susceptibility, are a more recently employed study design. GWAS have elicited new lines of enquiry into the etiology and pathogenesis of asthma. Cross-sectional surveys, in which the data and the means of collection are specified in advance and the study population is clearly defined, can be straightforward and inexpensive and are attractive to scientists studying the epidemiology of asthma.15 Cross-sectional studies also allow exposures and disease status to be assessed simultaneously among individuals in a well-defined population. There can be a specific interval, such as a given calendar year during which a community-wide survey is conducted, or a fixed point in the course of events that varies in real time from person to person.16
Occupational Cancer
Peter G. Shields in Cancer Risk Assessment, 2005
Occupational epidemiology is fundamentally concerned with the often-difficult task of relating exposure to outcomes. As a result, accurate exposure assessment has been described as the Achilles heel of the discipline. Limited or inaccurate information of a worker’s exposure can lead to misclassifica-tion and weakening of the exposure-outcome assessment. This problem is exagerated in evaluating diseases of long latency. Clearly, as time passes, accurate retrospective exposure assessments can become increasingly problematic. As discussed earlier, the ideal epidemiologic study for assessing exposure-outcome relationships is the prospective cohort study, in which exposure is well categorized and health effects are properly assessed and followed into the future. Such ideal circumstances, however, are rarely present.
Understanding Studies of Resistant Organisms: Focus on Epidemiologic Methods
Robert C. Owens, Lautenbach Ebbing in Antimicrobial Resistance, 2007
In a cohort design, patients are entered into the study based on the presence or absence of an exposure (or risk factor) of interest (Fig. 1). These two groups (i.e., those with the exposure and those without the exposure) are then compared to determine if they differ with regard to development of the outcome of interest. Whether a cohort study is prospective or retrospective depends on when it is conducted with regard to when the outcome of interest occurs. If patients are identified as exposed or unexposed and then followed forward in time to determine whether they develop the outcome, it is a prospective cohort study. If the study is conducted after all outcomes have already occurred, it is a retrospective cohort study. As an example, one might identify all patients who receive a FQ in the hospital (i.e., the exposed) and compare them to patients who do not receive a FQ (i.e., the unexposed). These groups could then be followed forward to determine what proportion of patients in each group develops the outcome of interest (i.e., FQREC infection).
A pilot study on the association between SLCO1B1 RS4363657 polymorphism and muscle adverse events in adults with newly diagnosed dyslipidaemia who were prescribed a statin: the Malaysian primary health care cohort
Published in Biomarkers, 2019
Subashini C. Thambiah, Meor Fairuz Rizal Meor Anuar Shuhaili, Boon How Chew, Intan Nureslyna Samsudin, Hejar Abdul Rahman, Johnson Stanslas, Shariful Hasan, Zalinah Ahmad
It is important to note that this study had its strengths being a prospective cohort study as it was able to establish a temporal relationship between the exposure and outcome of interests. Being focussed on SLCO1B1 gene, it provides specific data related to this gene, in particular rs4363657 SNP. However, there are limitations of this study including the lack of assessment of different types of statins as well as their dosages. Substantial differences in the pharmacokinetics of statins lead to conflicting results on genetic studies on susceptibility to SAMAE. Although self-reporting of SAMAE was verified by the doctors based on Table 1, to prevent subjective over-reporting, future studies should incorporate electromyelogram (EMG) and nerve conduction study (NCS) to support the existence of SAMAE. Being a pilot study, the small sample size gave rise to overestimated OR. Larger epidemiological cohorts with a greater number of polymorphisms throughout the entire genome or throughout a single gene with well-designed strategies such as comparative genomics, genome-wide screening and intermediate phenotype approach for identifying the genes that contribute to muscle adverse events are recommended. Other genes, which are strongly associated with muscle adverse events such as COQ2 gene, CYP3A4 gene, CYP3A5 gene and CYP2D6 gene should also be studied.
Effectiveness and safety of nivolumab in the treatment of lung cancer patients in France: preliminary results from the real-world EVIDENS study
Published in OncoImmunology, 2020
Fabrice Barlesi, Adrien Dixmier, Didier Debieuvre, Christophe Raspaud, Jean-Bernard Auliac, Nicolas Benoit, Pierre Bombaron, Denis Moro-Sibilot, Clarisse Audigier-Valette, Bernard Asselain, Thomas Egenod, Audrey Rabeau, Jérôme Fayette, Myriam Locatelli Sanchez, Jean-Luc Labourey, Virginie Westeel, Pauline Lamoureux, François-Emery Cotte, Victoria Allan, Melinda Daumont, Juliette Dumanoir, Dorothée Reynaud, Christophe Yannick Calvet, Nicolas Ozan, Maurice Pérol
To date, there have been few large-scale prospective real-world studies reporting the effectiveness and safety of nivolumab treatment in advanced NSCLC patients in Europe. The major strength of a prospective cohort study is the accuracy of data collection with regard to exposures, confounders and endpoints.13 Instead, data have been reported from small patient cohorts, retrospective studies and early access programs, for which inclusion/exclusion enrollment criteria may be restrictive.13–27 Due to known variation in cancer survival rates across Europe,28 country-specific data may be more appropriate to describe the real-world experience with nivolumab in the treatment of NSCLC. Furthermore, data collected in the context of a real-world study can also help to address important clinical evidence gaps such as the outcomes in patients who were underrepresented in, or excluded from, pivotal clinical trials of nivolumab due to more severe comorbidities or poor prognostic factors.
Trajectories of disability in activities of daily living in advanced cancer or respiratory disease: a systematic review
Published in Disability and Rehabilitation, 2022
Lucy Fettes, Josephine Neo, Stephen Ashford, Irene J. Higginson, Matthew Maddocks
A prospective cohort study is an effective and appropriate way to observe trajectories of ADL disability as it allows for as many variables as required to be studied in order to determine any association with the outcome and allow all relevant confounding variables to be rigorously collected [59]. The sample should accurately reflect advanced cancer or respiratory disease using appropriate inclusion criteria [59], and use of multiple sites helps to widen recruitment and generalizability, and small samples can be pooled for increased power [60–62]. It is important to be aware that the efficiency of a prospective cohort study increases as the incidence of a particular outcome increases [59], which means it is necessary to recruit participants who are at risk of functional loss. Gatekeeping of the more unwell or disabled participants by clinicians can be prevented by use of a trained research assistant to screen for eligible participants [63].
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