Study Design, Population, Methodology, and Statistical Analysis
The study by McCann, Yeh, Rodabaugh, & Moysich (2009) explore the relationship between tea and coffee consumption a reduction in endometrial cancer (EC). Several research projects have examined the link between endometrial cancer and diet. However, few studies have narrowed down on tea and coffee (Merritt et al., 2015). Therefore, McCann et al., 2009 discusses the association between the consumption of beverages and the risk of endometrial cancer. The drinks under study include decaffeinated coffee, caffeinated coffee, and tea. The investigators researched from the year 1982 to 1998. The study involved 541 women having cancer and other 541 women without the complication to act as a control to the investigations.
This essay will provide an overview of the study by McCann et al., 2009, exploring the study design, target population, methodology, and statistical analysis. It will also appraise the results and findings of the research question. The write-up will also evaluate the internal validity of the paper. Furthermore, it will explore the causality issues in the epidemiology research paper. Finally, the essay will analyze the external validity of the document to other target groups.
Study design, Population, Methodology, and Statistical analysis
The investigators applied Randomized control method as the study design. The study population involved 1082 women. 541 individuals involved had endometrial cancer, while the other 541 acted as a control to the study. The researchers obtained the study population from the Roswell Park Cancer Institute situated in New York’s Buffalo. The investigators issued epidemiologic questionnaires to the randomly selected women at the cancer institute. 50% of those who received the surveys filled and returned them to the investigators. The questionnaires covered a variety of issues ranging from alcohol consumption to diet.
The investigators used the SAS method to analyze the data received from the women. What the SAS used was compatible with version 9.1 of Windows (Breßler, Kohlbrecher, & Thünemann, 2015). The researchers limited the data analysis to questionnaires with complete information about the relationship between tea, decaffeinated coffee, and coffee and endometrial cancer. The investigators applied the t-test to access the continuous variables. However, the researchers used chi-square to access the categorical variables. The study categorized beverage consumers as follows: those who do not consume beverages, a half cup per day, and one to two cups per day. Furthermore, those individuals who drink less than two cups of beverages per day had their category.
Women who consumed more than two cups of coffee per day recorded a twenty-eight percent (28%) reduction in EC risk in comparison to nondrinkers (McCann et al., 2009). However, the researchers did not record an association between cancer and consumption of decaffeinated coffee. Women who took more than two cups of tea per day registered a forty-four percent (44%) reduction in EC risk in comparison to non-drinkers. Furthermore, the women who took more than four cups of both tea and coffee registered a fifty-three percent (53%) reduction in EC risk.
The authors begin by acknowledging the fact that the relationship between endometrial cancer and the beverages has been inadequately covered in the previous literature. The findings indicate that the consumption of coffee and tea reduces the risks of getting endometrial cancer. Tea consumption decreases the risk of tumor more than coffee intake by the case and the control. Furthermore, consuming more than four cups of both beverages reduces the risk of cancer more than taking an individual drink. However, the study does not indicate the association between endometrial cancer and decaffeinated coffee. Beverages contain phytochemicals which affect carcinogenesis (Singh, Prateeksha, Rawat, Bhagat, & Singh, 2017). Additionally, tea contains elevated amounts of theaflavins and catechins; hence making it more viable than coffee (Zhou et al., 2016).
Results and Findings of the Research Question
All in all, this is a time-sensitive and well-designed research, offering essential literature on the relationship between endometrial cancer and beverage consumption. The data allows the reader to understand the association between tea, coffee, and decaffeinated coffee and cancer (McCann et al., 2009). The reliability and the validity of the instruments gauging the covariates are robust and have few non-differential errors. Therefore, the study is a valuable source of information on beverages versus cancer (Yeganeh, Harrison, Vincent, Teede, & Boyle, 2018).
The investigators have presented the results using open tables. Chance variation cannot affect the data since the information on beverage consumption by women with or without EC is readily available (Forero et al., 2018). Selection bias is another barrier that can affect the validity of given research (Taylor, Fossey, & Kielhofner, 2017). Preference can be regarding gender, weight, or even skin color. However, the authors consider the common variables in endometrial cancer research like higher BMI, application of OC, and HRT among cases in comparison to the controls. Therefore, the above considerations eliminate the aspect of selection bias. Additionally, endometrial cancer only affects women; therefore, gender bias is non-existent since the controls, and the cases are all women.
Apart from the issues of selection bias, confounding concerns are also significant threats of research findings (Gallego et al., 2015). The extensive data on the epidemiology of EC permitted the researchers to provide reasons for confounders in their analyses. However, some drawbacks jeopardize the internal validity of the study results. The exposure and the characteristics of the general public can differ from those of individuals at the Roswell Institute of Cancer. Secondly, the researchers lacked accurate data on the size of beverage consumption. The investigators did not note the differences in the cup sizes that the women used to consume the beverages.
The control, just like the case women were patients of the Roswell health facility. Therefore, the control may have altered their diet before administration to the hospital. Similarly, there is a possibility that the patients of endometrial cancer would have also altered their diet before visiting the health facility. The alteration in food is a possible cause of attenuation in the estimates observed by the investigators (Obermair et al., 2016). Apart from the mentioned limitations, the research possesses internal validity.
Appraisal of Causality Inference
The research by McCann et al., 2009 is a case-control study that examines the relationship between the consumption of beverages and endometrial cancer. Several studies have explored the relationship between the complication and diet. However, few investigations like this one by McCann et al., 2009 have investigated the association between the disease and beverages like coffee and tea. Therefore, the study confirms that the consumption of beverages reduces the risk of contracting endometrial cancer (Ellis, 2017). The findings also confirm a dose-response association between exposure and outcome. The results indicate that women who are consuming beverages are at a lower risk of endometrial cancer than those who do not take drinks. The researchers collected data on beverage consumption before getting the outcome; this approach supports a hypothesis on the causal association.
Internal Validity of the Paper
The data provided in the study proves the causal association between beverages and endometrial cancer. There is also a relationship between tea consumption and endometrial cancer in obese women. Additionally, the intake of coffee work best for women having normal weight. Therefore, during experimentation, the researchers should suggest tea to overweight women and coffee to those with a healthy weight. Matching the beverage with the different sizes leads to desirable results. Apart from drinks, obesity is also a risk factor for the complication (Brown, McNair, Szalacha, Livingston, & Hughes, 2015). An increase in body weight increases the chances of developing endometrial cancer. Eating fatty and carbohydrate-rich food elevates the possibilities contacting the complication. However, eating fat-free food decreases the chances of a woman to develop cancer. Therefore, obesity also has an association with endometrial cancer.
The researchers studied the link between coffee, tea, and endometrial cancer in a limited environment which is at the Roswell hospital. EC patients outside the hospital may have different exposures and personal characteristics towards the complication. Therefore, there is a possibility that, patents at home may not record a reduction in the EC risk due to beverage intake. Additionally, the researchers did not consider the size of beverage cups used by various cases and controls (O’Brien, & Sali, 2017). It is possible that those that used big cups recorded a lower cancer risk than the individuals who used small cups. The possibility can create room for hypothesis modification. The investigators also used controls from the hospital. It is possible that commands from the general public can record different results from those at the health facility.
The study has various strengths and limited drawbacks which makes it valid for populations outside the USA. The authors indicate that a recent study confirmed the relationship between beverages and cancer in Japanese women (McCann et al., 2009). Therefore, Japan and other Asian countries can rely on research to manage the disease. Additionally, tea and coffee are beverages that individuals consume all over the world (Takechi et al., 2018). The study by McCann et al., 2009 lacks gender bias as cancer only affects women. The research investigates the impacts of beverage consumption in women with the disease and those without the complication. However, the study is limited to a hospital set-up as it bases on women at the Roswell Institute of cancer. Therefore, it may not have similar impacts to the general public.
The sample size is large, giving a simplified representation of the total population. The researchers randomly selected 541 women with EC and another 541 without the complication to act as a control. Apart from the sample size, the investigators considered other essential parameters; hence, qualifying the application of the research to all parts of the world. The study finds the effects of beverage consumption among obese and non-obese women. The analysis also considers the impacts of coffee and tea on young and old women who are past their menopause. The findings also investigate the effect of education on the relationship between beverages and endometrial cancer (Pálsdóttir et al., 2016). The results also consider the impact of the study on the smoking history of both the cancer patients and the control women. Therefore, the broad spectrum of the research makes it valid for worldwide usage.
Causality Issues in Epidemiology Research Paper
Apart from the various strengths, a few drawbacks can make other researchers question the global outlook of the research. The investigators based their study on patients of Roswell Cancer Park Cancer Institute in New York. Additionally, the researchers are all from Buffalo in New York. Readers from outside New York can easily assume that the findings are only viable within the capital city. Certain individuals do not take coffee and tea (Shivappa, Steck, Hurley, Hussey, & Hébert, 2014). Therefore, the researchers should address such groups of persons. The researchers conducted their study between the years 1982 to 1998. A section of readers can view the research as an old study and fail to apply it in the current century.
Conclusion
Despite the few challenges facing the study, the authors succeed in explaining the relationship between beverages and endometrial cancer. The researchers apply the randomized control design to conduct the investigation. The study population involves 541 EC patients and another 541 control women from the Roswell Park Cancer Institute. The research applies questionnaires to collect data from the case and the control women. Statistical analysis is through the SAS that the researchers use Windows 9.1 version to achieve. The findings show that the consumption of coffee and tea reduces the risk of endometrial cancer. The researchers further discuss the beverages reduces the chances of contacting the complication.
The findings are valid to the research on the relationship between endometrial cancer and beverages. The study lacks any form of bias like the gender or sample size questions. The EC is limited to women, at the same time, the sample population is women. Confounding concerns are not an issue since extensive data exist on consumption of beverages by women. The investigators also exhibit a causal association between coffee, tea, and endometrial cancer. However, there is also an association between obesity and EC. Readers can apply the findings worldwide; since coffee and tea are global beverages.
References
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