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PHE5EPI Epidemiology 1 Questions: Case Study: Read: Physical activity and risk of coronary heart disease in India by Rastogi et al., (2004). Area 1:  Describe the evidence presented in the paper you selected. Specifically address the following questions: -What was the exposure or intervention? -What was the outcome? -What was the study design? -What was the study population? -What were the main findings?  Area2: To what extent can the observed association between the exposure and outcome be attributed to non-causal explanations? Consider the following questions in your critique: -Are the results likely to be affected by selection and/or measurement bias? -Are the results likely to be affected by confounding? -Are the results likely to be affected by chance variation? Area 3: Do you think there is evidence of a causal association between the exposure and the outcome? This question relates to the internal validity of the study. Consider the following questions in your critique: -Is there a temporal relationship between exposure and outcome? -Is there a strong relationship between the exposure and the outcome? -Is there a dose-response relationship between exposure and the outcome? -Are the results consistent within the study?  Do the findings accord with other evidence? Specifically: -Are the findings consistent with other evidence, particularly evidence from studies of similar or more powerful study design? -Are the results plausible in terms of a biological mechanism? Area 4: Are the findings externally valid, that is generalisable? Specifically: -Can the findings be applied to the source population from which the study population was derived? -Can the study results be applied to other relevant populations? Answers: Area 1 01: What was the exposure or intervention? The research study by Rastogi et al., (2004) presented a study on the relation between physical activity and coronary heart disease (CHD) risk in urban areas in India. Although the association between physical activity and CHD has been extensively studies in western population, however the impact of physical activity and CHD risk within India has not been studied. As physical inactivity has become particularly predominant in urban areas of India, conducting this research study became important. The intervention for the study included providing leisure time exercise intervention to patients with diagnosis of Acute Myocardial Infarction (AMI) in urban hospitals of New Delhi and Bangalore to explores the link between exercise and CHD risk. Healthy controls were also taken to analyze the difference in result. 02: What was the outcome? The physical activity levels of the participants selected in the study was assessed by means of physical activity questionnaire. This tool was a mean to analyze the energy expenditure per day in the area of work, leisure time exercise, sedentary activities and  other work in each participant. The outcome of the study showed that 48% of controls participated in leisure time activities such as walking, jogging, gardening, sports and yoga. However, only 38% cases participated in leisure time exercise and they spent maximum time on sedentary activities like music, watching television and other activities. It was also found that those with high level of engagement in leisure time exercise were older, more educated, used less number of cigarettes and had less family history of CHD. On the other hand, people with most sedentary lifestyle had increased prevalence of family history of CHD, had high socioeconomic status and consumer more cigarettes. Work related activity was mostly found in younger educated group who had very less leisure time activity (Rastogi et al., 2004). 03: What was the study design? A hospital based case control study design was adapted by Rastogi et al., (2004) to conduct the study and analyze the difference in risk factors of CHD and leisure time exercise in case and control group. 04: What was the study population? Eligible cases for the cases included patients within the age of 21-74 years with diagnosis of incident AMI in urban hospitals of New Delhi and Bangalore. Patients who had previous history of myocardial infarction were excluded as this would have altered the exposure to risk factor in participants. The control group for the study included healthy individual with minor health issues recruited from non-cardiac outpatient clinic (Rastogi et al., 2004). 05: What were the main findings? The analysis of the time spent in different types of activities, risk and lifestyle present in case, and control group revealed that sedentary lifestyle was the positive factor contributing to risk of CHD. On the other hand, leisure time exercise of 35-40 minutes duration acted as a protective factor for reducing the risk of CHD. Hence, this finding reflects the adverse impact of physical inactivity among people and presents the need for public health activity in promoting regular physical exercise among urban population of India.  This would alter the biological mechanism that leads to CVD risk. Area 2:  01: Are the results likely to be affected by selection and/or measurement bias? In the epidemiological studies, the population characteristics are measured. The parameters that are studied are the exposure prevalence, disease rate and may be the measurement of the exposure and disease association. Measurement bias or the systematic error is the use or favoring of a particular result. The measurement process is said to be biased when the true value of the measurement is understated or overstated in a research. It is a part of the design in qualitative study (Schmidt & Hunter, 2014). In the paper, the study is conducted on the people and there are ethical constraints and attendant practical, they are invariantly subjected to bias. The paper by Rastogi et al., (2004) has also qualitative design, so it is clear that the measurement bias is not completely eliminated. There are potential chances that the study outcomes can be affected in both ways; understated or overstated. In the chosen paper, for the subjects, the leisure time activity was used at different levels. This acts as a variable that is judged against the dimensions or at different levels. This shows that the study outcomes have a chance of measurement bias that has an effect on the study outcomes. 02: Are the results likely to be affected by confounding? In epidemiological studies, confounders are the third variables that are incorrectly appear that the outcome is seen associated with the observed exposure (Thompson & Arah, 2014). It is an unobserved exposure that is found associated with the exposure and is considered to be a potential cause for the outcome. It has also significant potential to affect or manipulate the study outcome. In the chosen paper, the subject population exposure was leisure time activity that is considered to be equivalent to brisk walking for 36 minutes and how it has a significant effect on the reduction of coronary heart disease risk. There are also other confounding factors that are found associated with the unhealthy lifestyle choices like dietary habits, drinking, smoking which are also the equal contributors and important factors in the risk for the coronary heart disease that are standardized in the procedure of data analysis. Therefore, these confounding factors are not the potential reasons for the bias in the study outcomes. The factors that might have a negative effect on the study outcomes were not considered and selection bias is present in the study. Hospital setting was taken for the research study in place of the entire population illustrates that there might be a view of biasness in the coronary heart disease incidence as compared to the entire population research setting. 03: Are the results likely to be affected by chance variation? Chance variation in the statistical analysis is the difference between the expected and the derived outcome of the study. In any statistical model, the chance error or chance variation is the difference between the actual variable value and the predicted variable value in the research study. These factors influence the variable behavior in question that behave in a random fashion. In the same way, the chance errors and outputs behave in a random manner that cannot be controlled; however, this does not reduce the model credibility. In the chosen paper, the leisure time physical activity may reduce the coronary heart disease risk in the chosen subjects as compared to sedentary life.  The hypothesis was successfully proved by the result of the study, therefore, there is no chance variation in the research study. Area 3:  01: Is there a temporal relationship between exposure and outcome? A temporal relationship is defined as the timing applicable between a factor and an outcome that may be further attributed to the preponderance to an event. In simple terms, it is applicable to time association between cause and effect. Normally, at instances where temporal relationship prevails, a chain of events precedes one another that lead to the ultimate outcome of the study. In this particular study, the exposure has been the leisure time physical activity while the outcome has been the risk of prevalence of coronary heart disease (CHD) among the chosen subjects (Kizilbash et al., 2006). However, the chosen population of subjects for the study was that of the patients who have been predisposed to condition of acute myocardial infarction compared against the age and sex matched controls who have been hospitalized in definite settings. Therefore, pertaining to this research study, there is no scope for any presence of any temporal relationship as the experimental group of subjects is already predisposed to condition of acute myocardial infarction thereby allaying the causal association between exposure and outcome. 02: Is there a strong relationship between the exposure and the outcome? Review of the findings and methodology adopted in course of the study, it is evident that there exists a strong relationship between the exposure due to leisure time physical activity and the outcome of the relatively lesser risk for development of CHD. 48% of the control subjects were engaged in participation to leisure time exercise in contrast with the 38% of the experimental subjects. The relative risk assessment data showed that subjects accustomed to highest level of leisure time exercise represented a risk of 0.45 whereas those engaged in non-work sedentary activity demonstrated an elevated risk of 1.88 towards the propensity for being afflicted by CHD. Therefore, the presence of this considerable difference in relative risk measures is proof enough to demonstrate that there remains a strong relationship and potential association between the exposure and outcome. The exposure being the leisure time physical activity might exert sufficient impact in terms of the projected outcomes of lesser propensity to encounter CHD. 03: Is there a dose-response relationship between exposure and the outcome? The dose-response relationship refers to the measurement of relationship between variable levels of exposure to a definite quantity of the substance and the overall impacts on the outcomes set for the research study. In case of an exploratory research, various confounding factors of both internal as well as external types seem to exert their corresponding influences upon the outcomes that are likely to be generated in course of the study (Van Roie et al., 2017). Therefore, it is imperative for researchers to ensure that methodological bias because of the abundance and presence of confounding factors does not stall the credibility of the research. In this context, the application of the various levels of interventions is a worthy option to mitigate the problem due to bias. The attachment of various levels of leisure time activities and effect on reduction of risk of development of CHD thus reduces the occurrence of bias. Hence, the analysis of the differential doses of exposure is indicative of the presence of the dose response relationship in the study. 04: Are the results consistent within the study? The results and discussions carried out with respect to the study is suggestive of the fact that there exists an inverse relationship between the exposure to leisure time physical activity and the chances of suffering due to CHD in the subjects. The differential exposure to various levels of exercise depicted that with the attainment of the maximum amount of exercise, the chance of occurrence of CHD remains low. On the contrary, participation to least amount of leisure time physical activity has been associated with the increased chance of occurrence of CHD. The incremental level of exposure to leisure time exercises shows that the relative propensity to develop CHD decreases following increased participation. Therefore, it may be well concluded that the results are consistent within the study without depicting any contradictory findings and explanations that do not fit into the outcomes of the research. 05: Are the findings consistent with other evidence, particularly evidence from studies of similar or more powerful study design? For a research study to be valid, it is imperative to relate and compare the findings of the study undertaken with that of the other similar studies showing suitable and pertinent along with in some cases more powerful study design. The potential impacts of physical activity specifically of the leisure time exercises and the impacts on coronary heart diseases has been the topic of investigation in the research under consideration. CHD being a throbbing global health issue have garnered attention of the research and clinical communities across the globe to provide holistic and effective resolutions to this nagging problem. Therefore, the present study holds extreme relevance in this regard to offer further insight and deeper probe into the matter. Studies by Le et al., (2014), has thrown light upon the benefits derived from participating in leisure time physical activities. Their findings succinctly described and fostered for the efficacy of the running as a part of the leisure time physical activity that possess the marked potential of decreasing the risks of mortality from all causes and cardiovascular disease. Hence, attainment of substantial mortality benefits has been recommended in case of the sedentary individuals who tend to shy away from doing any physical activities. Furthermore, another study performed by Gielen et al., (2015) highlighted the prognostic and symptomatic benefits of exercise training for ameliorating condition with respect to various forms of cardiovascular diseases. Implementation and following of novel and innovative training methods like that of high intensity interval training as well as resistance training have been found to be beneficial under such circumstances. Thus, the findings as depicted in the chosen article with respect to other findings have been found to corroborate well thereby enhancing the credibility, validity and reliability of the research performed. 06: Are the results plausible in terms of a biological mechanism? The results that have been obtained in course of the study suggest that they are extremely plausible in terms of a biological activity. Research has consistently highlighted on the efficacy of the exercise interventions in harboring optimal and positive outcomes because of the procured benefits from participation in physical activities. The potential impacts on the cardiovascular system in addition to the refinement and enriched supply of oxygen in the body tissues add to the benefits derived from participation in definite exercise regime. Research has brought to the forefront the vital finding that leisure time physical activity and specifically of moderate to vigorous intensity type, has been pivotal in maximizing the longevity benefit. Thus, mortality due to cardiovascular health issues are significantly reduced following engagement in leisure time physical activity (Arem et al., 2015). Thus, it is justified to support the results by relating to possible biological mechanisms as represented through and may be corroborated in terms of other relevant findings done in similar contexts. Area 4:  01: Can the findings be applied to the source population from which the study population was derived? The findings of the study cannot be applied to the source population from which the study population had been derived. This is because random sampling was no done to reach to the final sample population; in contrast, a number of screening factors were considered for deciding on to the study population. For a study finding to be applied to the source population from which the study population has been derived, it is essential that random sampling has been done.  Random sampling refers to the fundamental form of sampling where a sample is selected from a larger population solely by chance. In such a case, every individual has an equal opportunity to be a part of the sample population for the study (Panneerselvam, 2014). In the present study, no such random sampling could be done, and individuals are meeting the inclusion criteria for the study were only included in the final research. Eligible candidates were patients with age between 21 and 74 years who were admitted to one of the eight urban hospitals in Bangalore and New Delhi. The eligibility criteria for the study were met by 419 individuals. 350 were finally included in the study depending on the exclusion criteria of discharge, death, sickness and absence of consent. 02: Can the study results be applied to other relevant populations? Applying the results of a study to other relevant populations is known as generalisability. Generalisability of a study refers to the extent to which the findings of a research study can be applied to different settings other than the one in which the original experiment has been conducted. The findings can be applied to other relevant settings if the external validity is strong enough (Matthews & Ross, 2014). For the present research, the study results cannot be applied to other relevant population. For a study result to be applied to other similar populations, it is crucial that the sample is a representative of the source sample, the results have high ecological validity and the results have been replicated. The participants recruited in the study were of age between 21 and 74 years. Therefore there is a need for the study to be replicated with samples with the same age group. In addition, the study was conducted in two hospitals, one in Bangalore and one in New Delhi. For a study to have generalised results, it is pivotal that the study is conducted across a number of settings from which the participants are to be extracted. The study also is marked with potential sources of bias including the selection of control as well as differential recall among cases compared with control groups. The researchers had not taken up necessary steps to avoid this form of bias. Lastly, the study was conducted with patients admitted only in urban hospitals and rural hospitals were not included in the study. This is significant as the results might be different for patients who are from rural background. Health behaviour and health outcomes of individuals residing in urban areas and rural areas vary significantly on different incidences depending on the outcomes being assessed. It is therefore advisable that study findings from rural areas are not considered similar for urban areas and vice versa (Robson & McCartan, 2016). References Arem, H., Moore, S. C., Patel, A., Hartge, P., de Gonzalez, A. B., Visvanathan, K., … & Linet, M. S. (2015). Leisure time physical activity and mortality: a detailed pooled analysis of the dose-response relationship. JAMA internal medicine, 175(6), 959-967. Gielen, S., Laughlin, M. H., O’Conner, C., & Duncker, D. J. (2015). Exercise training in patients with heart disease: review of beneficial effects and clinical recommendations. Progress in cardiovascular diseases, 57(4), 347-355. Golafshani, N. (2003). Understanding reliability and validity in qualitative research. The qualitative report, 8(4), 597-606. Kizilbash, M. A., Carnethon, M. R., Chan, C., Jacobs, D. R., Sidney, S., & Liu, K. (2006). The temporal relationship between heart rate recovery immediately after exercise and the metabolic syndrome: the CARDIA study. European heart journal, 27(13), 1592-1596. Lee, D. C., Pate, R. R., Lavie, C. J., Sui, X., Church, T. S., & Blair, S. N. (2014). Leisure-time running reduces all-cause and cardiovascular mortality risk. Journal of the American College of Cardiology, 64(5), 472-481. Matthews, B., & Ross, L. (2014). Research methods. Pearson Higher Ed. Panneerselvam, R. (2014). Research methodology. PHI Learning Pvt. Ltd.. Rastogi, T., Vaz, M., Spiegelman, D., Reddy, K. S., Bharathi, A. V., Stampfer, M. J., … & Ascherio, A. (2004). Physical activity and risk of coronary heart disease in India. International journal of epidemiology, 33(4), 759-767. Robson, C., & McCartan, K. (2016). Real world research. John Wiley & Sons. Schmidt, F. L., & Hunter, J. E. (2014). Methods of meta-analysis: Correcting error and bias in research findings. Sage publications. Thompson, C., & Arah, O. (2014). B4-4: A Novel Technique for Analysis of Uncontrolled Confounding in Non-experimental Comparative Effectiveness Research. Clinical medicine & research, 12(1-2), 108-108. Van Roie, E., Delecluse, C., Coudyzer, W., & Bautmans, I. (2017). Strength gain and functional benefits of resistance training: dose-response relationship. In Osteoporosis International (Vol. 28). Springer International.

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