Introduction To Epidemiology And Critical Appraisal Of Research Studies

Overview of the journal

Critical appraisal of an article can be described as a systematic process which evaluates the strengths and the weakness of a study or a research article. This is done to assess to research findings and he validity of the findings. The most important part of a critical appraisal of a study is the proper evaluation of the research questions whether the study design is carried in a proper way and it also takes into account of the several key methodologies that are featured in a design. The other factors that are also considered include the applicability of the statistical methods used and the subsequent interpretation methodology used in the study process (Patterson & Dawson, 2017). In this study an article titled “Higher regular coffee and tea consumption is associated with reduced endometrial cancer risk” will be critically appraised. This critical appraisal will include the overview of the journal, appraisal of internal validity of the findings, appraisal of the causality inference, and the appraisal of the internal validity.

The chosen article focuses on the regular higher consumption of tea and coffee leads to the reduction of the cancer risk. As per the American Cancer Society in the year 2007, a total of 39080 women were diagnosed with the endometrial cancer and a total of 7,400 women are found to be dying from the endometrial cancer. The risk factors established in the case study all direct towards the hormonal aetiology. Several factors like the late menopause, obesity, infertility and early menarche has its relations with the increased exposure to the endogenous oestrogen. Thus, an important inference is that all these factors are related directly with the endometrial cancer. However, it is important to note that the obesity has it direct link with the endometrial cancer and it occurs specifically in women that is undergoing post menopause changes. Similarly, a reduced incidence of the endometrial cancer is noticed within the pregnant women due to the high levels of progesterone secretion and in comparison to the oestrogen. A large number of studies are done on the effect of diet on the endometrial cancer. However, only few studies have focussed on the consumption of tea and coffee and its impact on the endometrial cancer. The important part is that the globally both tea and coffee are widely consumed. The substantial sources of lignans, isoflavins, cathechins, flavonoids and the other polyphenolic compounds. It has been shown in experimental studies that polyphenols are potent in inhibiting the carcinogenesis through the anti-inflammatory, anti-hormonal and anti-oxidant mechanisms. However, it is also important to mention that these beverages also contain a large amount of caffeine which has the potential of affecting the cell processes and is both the inhibitor and promoter of carcinogenesis (McCann et al., 2009).

Materials and methods used in the study

Materials and methods used in the study- The study was carried out in a Roswell Park Cancer Institute in New York and the data are collected through a Patient Epidemiologic Data Systems (PEDS). The data were collected from the span of 1982 to 1998 and it the data collection was approved by the International Review Board. During this time period, questionnaires were offered to the patients. It is important to highlight that the PEDS questionnaire is self-administered. PEDS questionnaires are used to cover the information on the diet, vitamin usage, medication, medical histories, reproductive histories, environmental exposures, occupational exposure, family history of cancer, alcohol and tobacco consumption. All the statistical analysis is carried out in a SAS version 9.1 in windows. For this study only women are selected that have the complete data on tea, decaffeinated coffee, and data on coffee. Thus, a total of 512 control and 513 cases of were included in the study (McCann et al., 2009).

Results of the study- the results of the study indicate that with the consumption of more than 2 cups of coffee per day, within both the heavier and the normal weight women shows a slight reduction in the overall reduction of the endometrial cancer risk. This founding is a analysis conducted through an stratified analysis. While in the unstratified analysis, no relationship has been found between the consumption of the decaffeinated coffee and the endometrial cancer. The coffee consumption has positive effects on the reduction of cancer only in the heavier women. It has been

Discussion- the discussion section highlights that the authors have noticed an inverse association between the consumption of tea and coffee and the endometrial cancer risks. However, no association has been noticed in the consumption of the decaffeinated coffee. However, it is important to mention that the caffeine has a positive role in the aetiology of the endometrial cancer. The estimates observed with the consumption of the tea and coffee has a very similar type of analysis found for tea alone. This suggests that tea alone is much more effective than the coffee (McCann et al., 2009).

To put it briefly, this study is robust and well-designed analysis of hospital based case study which intends to improve on previous research performed in the area of endometrial cancer risk. Studies have suggested that endometrial cancer risk is related to the dietary habits of an individual (Lukic et al., 2018). According to the author of this study, few research has been dedicated to study the effect of tea and coffee on endometrial cancer risk. Hence, this study enhances, improves and add new value to the field and not a derivative study. However, this study has some flaws regarding validity and reliability of the results and data.

Results of the study

The data source used for this study was data collected from Roswell Park Cancer Institute (Buffalo, New York) for the duration of 1982 and 1988. They used consumption of caffeine and black tea as independent variable. As an independent variable, they used different measure of caffeine and tea consumption for the study of dependent variable which is the risk of endometrial cancer. Although, the researchers have little control over the data as it is collected from Roswell Park Cancer Institute (Buffalo, New York). The authors have selected their data based on the available information but had no manipulative control over their data. However, evidence suggests that other authors have also followed the same type of research design. For example, Weiderpass et al. (2014) have also studied the relation between tea, coffee and endometrial cancer. Similar like the author of this article, Weiderpass et al. (2014) have also used the data collected from the woman residing in Sweden’s Upsala Health Care Region in the year 1991 – 92. However, they followed up their subject for almost 20 years whereas in this article’s data were only for the duration of 6 years. Therefore, it can be said that although the data collection method for both the research is same, the data quality is better for Weiderpass et al. (2014).

McCann et al. (2009) have mentioned some errors that can affect the results and interpretation of their analysis. They have mentioned in their study that the findings of their investigation is not statistically significant. This signifies that they cannot support their claim with 100 per cent confidence. They have found a link between the tea, coffee consumption and endometrial cancer but they can only suggest that it is a possibility. They cannot claim it with conviction. The confidence level of their study were set at 95 per cent. On the contrary, with similar experimental design, Weiderpass et al. (2014) have found their data statistically significant.

This study’s findings is in clear contrast with the findings from the study performed by Yang et al. (2015). Authors of this article suggests that there is a relation between tea, coffee consumption whereas Yang et al. (2015) have showed that there is no relation between tea consumption and endometrial cancer whereas there might be a weak link between coffee consumption and endometrial cancer. Authors of this article uses a sample pool of five hundred and forty-one woman with primary endometrial cancer and another five hundred and forty one randomly selected woman with intact uterus were selected as control group. On the contrary, Yang et al. (2015) have collected the data from 560,356 subjects from the UK Million Women Study. Thus, from the comparison, it can be inferred that data from Yang et al. (2015) are more much elaborate and statistically significant. This makes this article’s data in little bit weak position and academics will tend to refer and consider the data from Yang et al. (2015). To add more evidence, Weiderpass et al. (2014) has also did not find any relation between the tea, coffee consumption and endometrial cancer while Crous-Bou et al. (2016) have reported that coffee consumption reduced the risk for endometrial cancer whereas tea has no relation with it.

Discussion

To summarize, it can be this article is well-structured and experimentally sound in overall manner. This study is interesting and makes a novel approach in less discovered area of study. This study also very much relevant to current health situation. Although, it has some flaws. Findings of this study is not statistically significant does not mentioned or discussed whether the study was performed in an ethical manner. Along with that, due to statistically insignificant data does not make the findings very much reliable and their conclusion is contradictory to the findings reported by other studies in this research area.

As mentioned by the academics, causation can be defined as something which causes a difference. The difference that is causes have to be different from what would have happened without the causation (Beckers & Vennekens, 2018). This definition is generally accepted by the major experimentalists when interpreting the causation of a particular experiment. A causal inference can be two types: counterfactual approach and production approach.  A counterfactual approach is where there is a direct link between cause and effect which signifies that effect would not have been happened without the cause (Morgan & Winship, 2015). In case of production approach there is no significant idea that the cause is the main reason or only reason for the effect. The cause might not even responsible for the effect (Shipley, 2016).

This study by McCann et al. (2009) is analytic and observation case study based hospital data which is focussed on the correlation between dietary habits and endometrial cancer. The concerned dietary habits here are consumption of tea and coffee. McCann et al. (2009) have suggested a correlation between tea, coffee consumption and endometrial cancer. The report findings by McCann et al. (2009) here are suggestive and contradictory. Additionally, the findings reported by the McCann et al. (2009) are contradictory to the most of the similar studies investigated in the same research area (Weiderpass et al., 2014; Yang et al., 2015; Je & Park, 2015). Interestingly, all of the researches are performed in a basically similar design which puts the findings of this study in reflective view.

In this study, McCann et al. (2009) have suggested that there might be a relation or link between the tea, coffee consumption and endometrial cancer in woman. Their findings were not statically significant and authors have only suggested their conclusion. Therefore, it can be said that cause in this study is tea and coffee consumption while effect is endometrial cancer. From the above discussion, it can be inferred that causation (tea, coffee consumption) of this experiment has no direct link to the effect (endometrial cancer). Causation is not solely responsible for the effect. It might be one of the reasons for the effect or it might not be. Hence, from the causal inference theory, it can be deduced that the approach of this investigation is related with production hypothesis as it has been described earlier in this section.

Appraisal of internal validity

The correlation between the cause and effect of the article by McCann et al. (2009) is in support of contribution hypothesis. Contribution relation is when a cause is contributing towards the outcome and not solely responsible for it. There might be two or more factors for the causation to bring forward the effect. Hence, researchers have argued that most appropriate way to investigate a contribution is to how effect does a cause have on the outcome (Baiocchi, Cheng & Small, 2014). In case of this article, authors have suggested that tea and coffee might a cause to reduce the endometrial cancer which is the outcome. However, the authors do not delves into the fact in detail that whether this cause is the sole reason for the outcome. Furthermore, authors do not mention in their report that how much effect or influence the cause (tea, coffee consumption) have on the outcome (endometrial cancer) as it has been suggested in their report that cause might be the reason of outcome.

Both the tea and coffee contains caffeine and along with it many other phytochemicals that can affects the carcinogenesis. Additionally, it has been found by the authors that the caffeine affects the steroids hormone level and its positive association with the SHBG and plasma estrone and the inverse association with the plasma free testosterone and free estradiol. The findings of the authors have suggested that caffeine plays a role in the aetiology of the endometrial cancer. Primarily among the normal weight women, it has been found that coffee and tea consumption has played a major role in reducing the risk generated from the endometrial cancer. While it has been confirmed by Weiderpass et al. (2014), that there is no significant association between the consumption of coffee and tea with the endometrial cancer. while it has been put forward by the authors that there is a relation between the BMI and the endometrial cancer risk and additionally the other factors like parity, menopausal status, hormonal contraceptives. The best part of this study is the large population used for the study and thus it presents an applicability. While It has been highlighted by that the Yang et al. (2015), that there is a weak correlation between the higher coffee consumption and the and cancer risk in women that has a BMI of 35 and 30. While it is important to note that the tea and coffee is more efficient rather than the decaffeinated coffee in the reduction of the endometrial cancer and the effect of caffeine gets modified with the modifications in the body mass index. This finding has been confirmed through a study conducted by Je & Giovannucci (2012), that there is a potential association between the endometrial cancer risk and the coffee consumption. These studies are based on the 6 cohort studies, 10 case control and 16 observational studies which totals around 6,628 cases. The results of the study indicate that the increased consumption of coffee leads to reduced endometrial cancer risk.

Conclusion

From the above study it can be concluded that the endometrial cancer risk can be reduced by increasing the consumption of tea and coffee. It has been shown in experimental studies that polyphenols are potent in inhibiting the carcinogenesis through the anti-inflammatory, anti-hormonal and anti-oxidant mechanisms. However, it is also important to mention that these beverages also contain a large amount of caffeine which has the potential of affecting the cell processes and is both the inhibitor and promoter of carcinogenesis. The study has been presented in a critical way and it includes both the contradictory and supportive evidences which leads to the development of the fact that tea and coffee is beneficial for cancer prevention.

References

Baiocchi, M., Cheng, J., & Small, D. S. (2014). Instrumental variable methods for causal inference. Statistics in medicine, 33(13), 2297-2340.

Beckers, S., & Vennekens, J. (2018). A principled approach to defining actual causation. Synthese, 195(2), 835-862.

Crous-Bou, M., De Vivo, I., & Epidemiology of Endometrial Cancer Consortium. (2016). Coffee and tea intake and risk of endometrial cancer in the Epidemiology of Endometrial Cancer Consortium (E2C2).

Je, Y., & Giovannucci, E. (2012). Coffee consumption and risk of endometrial cancer: Findings from a large up?to?date meta?analysis. International journal of cancer, 131(7), 1700-1710.

Je, Y., & Park, T. (2015). Tea consumption and endometrial cancer risk: meta-analysis of prospective cohort studies. Nutrition and cancer, 67(5), 825-830.

Lukic, M., Guha, N., Licaj, I., van den Brandt, P. A., Stayner, L. T., Tavani, A., & Weiderpass, E. (2018). Coffee Drinking and the Risk of Endometrial Cancer: An Updated Meta-Analysis of Observational Studies. Nutrition and cancer, 70(4), 513-528.

McCann, S. E., Yeh, M., Rodabaugh, K., & Moysich, K. B. (2009). Higher regular coffee and tea consumption is associated with reduced endometrial cancer risk. International journal of cancer, 124(7), 1650-1653.

Morgan, S. L., & Winship, C. (2015). Counterfactuals and causal inference. Cambridge University Press.

Patterson, J., & Dawson, C. (2017). Critical Appraisal of Qualitative Literature. Perspectives of the ASHA Special Interest Groups, 2(13).

Shipley, B. (2016). Cause and correlation in biology: a user’s guide to path analysis, structural equations and causal inference with R. Cambridge University Press.

Weiderpass, E., Sandin, S., Lof, M., Oh, J. K., Inoue, M., Shimazu, T., … & Adami, H. O. (2014). Endometrial cancer in relation to coffee, tea, and caffeine consumption: a prospective cohort study among middle-aged women in Sweden. Nutrition and cancer, 66(7), 1132-1143.

Yang, T. O., Crowe, F., Cairns, B. J., Reeves, G. K., & Beral, V. (2015). Tea and coffee and risk of endometrial cancer: cohort study and meta-analysis–. The American journal of clinical nutrition, 101(3), 570-578.