Epidemiology Read the following two study abstracts, and answer the questions wh
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EpidemiologyRead the following two study abstracts, and answer the questions which follow each abstract. STUDY A: Objective: To determine the relation between stressful life events and difficulties and the onset of breast cancer. Design: Case-control study. Setting: 3 NHS breast clinics serving west Leeds. Participants: 399 women, aged 40-79, attending the breast clinics who were Leeds residents. Main outcome measures: Odds ratios of the risk of developing breast cancer after experiencing one or more severe life events, severe difficulties, severe 2 year non-personal health difficulties, or severe 2 year personal health difficulties in the 5 years before clinical presentation. Results: 332 (83%) women participated. Women diagnosed with breast cancer were no more likely to have experienced one or more severe life events (odds ratio = 1), or one or more severe difficulties (OR = 1) than women diagnosed with a benign breast lump. Conclusion: These findings do not support the hypothesis that severe life events or difficulties are associated with onset of breast cancer. 3A. What were the researchers interested in finding out (What is the exposure of interest? What is the health outcome of interest?)? 3B.What is the study design? Who are the cases? Who are the controls? 3C. What did they find, specifically? Interpret the odds ratio. 3D. What conclusions do the researchers draw from their findings? What do you think of their conclusions? 3E. What if the OR was 5? How would you interpret this? 5F. What if the OR was .2? Interpret this. Study B: Objective: To investigate the strength of association between past stressful life events and the development of breast cancer. Design: Case-control study. Subjects: 119 consecutive women aged 20-70 who were referred for biopsy of a suspicious breast lesion. Main outcome measures: Odds ratio of the risk of developing breast cancer after stressful life events in the preceding five years after adjustment for confounders. Results: 41 women were diagnosed as having malignant disease while the remainder had benign conditions. Severe life events increased the risk of breast cancer. The odds ratio was 3.2. Multiple logistic regression analysis showed that all severe events and coping with the stress of adverse events by confronting them and focusing on the problems significantly predicted a diagnosis of breast cancer. Non-severe life events and long term difficulties had no significant association. Conclusion: These findings suggest an aetiological association between life stress and breast cancer. 4A. What were the researchers interested in finding out (What is the exposure of interest? What is the health outcome of interest?)? 4B.What is the study design? Who are the cases? Who are the controls? 4C. What did they find, specifically? Interpret the odds ratio (or relative risk, as appropriate). 4D. What conclusions do the researchers draw from their findings? What do you think of their conclusions? 5. Why might the two studies have come to different conclusions? What might this difference in results say about the internal validity or external validity of each of these studies? Clearly, we don’t KNOW from viewing the abstracts, but, you should be able to come up with a reasonable explanation for this difference using the concepts of internal and/or external validity. Epidemiology
Read the following two study abstracts, and answer the questions which follow each abstract. STUDY A: Objective: To determine the relation between stressful life events and difficulties and the onset of breast cancer. Design: Case-control study. Setting: 3 NHS breast clinics serving west Leeds. Participants: 399 women, aged 40-79, attending the breast clinics who were Leeds residents. Main outcome measures: Odds ratios of the risk of developing breast cancer after experiencing one or more severe life events, severe difficulties, severe 2 year non-personal health difficulties, or severe 2 year personal health difficulties in the 5 years before clinical presentation. Results: 332 (83%) women participated. Women diagnosed with breast cancer were no more likely to have experienced one or more severe life events (odds ratio = 1), or one or more severe difficulties (OR = 1) than women diagnosed with a benign breast lump. Conclusion: These findings do not support the hypothesis that severe life events or difficulties are associated with onset of breast cancer. 3A. What were the researchers interested in finding out (What is the exposure of interest? What is the health outcome of interest?)? 3B.What is the study design? Who are the cases? Who are the controls? 3C. What did they find, specifically? Interpret the odds ratio. 3D. What conclusions do the researchers draw from their findings? What do you think of their conclusions? 3E. What if the OR was 5? How would you interpret this? 5F. What if the OR was .2? Interpret this. Study B: Objective: To investigate the strength of association between past stressful life events and the development of breast cancer. Design: Case-control study. Subjects: 119 consecutive women aged 20-70 who were referred for biopsy of a suspicious breast lesion. Main outcome measures: Odds ratio of the risk of developing breast cancer after stressful life events in the preceding five years after adjustment for confounders. Results: 41 women were diagnosed as having malignant disease while the remainder had benign conditions. Severe life events increased the risk of breast cancer. The odds ratio was 3.2. Multiple logistic regression analysis showed that all severe events and coping with the stress of adverse events by confronting them and focusing on the problems significantly predicted a diagnosis of breast cancer. Non-severe life events and long term difficulties had no significant association. Conclusion: These findings suggest an aetiological association between life stress and breast cancer. 4A. What were the researchers interested in finding out (What is the exposure of interest? What is the health outcome of interest?)? 4B.What is the study design? Who are the cases? Who are the controls? 4C. What did they find, specifically? Interpret the odds ratio (or relative risk, as appropriate). 4D. What conclusions do the researchers draw from their findings? What do you think of their conclusions? 5. Why might the two studies have come to different conclusions? What might this difference in results say about the internal validity or external validity of each of these studies? Clearly, we don’t KNOW from viewing the abstracts, but, you should be able to come up with a reasonable explanation for this difference using the concepts of internal and/or external validity. Epidemiology
Read the following two study abstracts, and answer the questions which follow each abstract. STUDY A: Objective: To determine the relation between stressful life events and difficulties and the onset of breast cancer. Design: Case-control study. Setting: 3 NHS breast clinics serving west Leeds. Participants: 399 women, aged 40-79, attending the breast clinics who were Leeds residents. Main outcome measures: Odds ratios of the risk of developing breast cancer after experiencing one or more severe life events, severe difficulties, severe 2 year non-personal health difficulties, or severe 2 year personal health difficulties in the 5 years before clinical presentation. Results: 332 (83%) women participated. Women diagnosed with breast cancer were no more likely to have experienced one or more severe life events (odds ratio = 1), or one or more severe difficulties (OR = 1) than women diagnosed with a benign breast lump. Conclusion: These findings do not support the hypothesis that severe life events or difficulties are associated with onset of breast cancer. 3A. What were the researchers interested in finding out (What is the exposure of interest? What is the health outcome of interest?)? 3B.What is the study design? Who are the cases? Who are the controls? 3C. What did they find, specifically? Interpret the odds ratio. 3D. What conclusions do the researchers draw from their findings? What do you think of their conclusions? 3E. What if the OR was 5? How would you interpret this? 5F. What if the OR was .2? Interpret this. Study B: Objective: To investigate the strength of association between past stressful life events and the development of breast cancer. Design: Case-control study. Subjects: 119 consecutive women aged 20-70 who were referred for biopsy of a suspicious breast lesion. Main outcome measures: Odds ratio of the risk of developing breast cancer after stressful life events in the preceding five years after adjustment for confounders. Results: 41 women were diagnosed as having malignant disease while the remainder had benign conditions. Severe life events increased the risk of breast cancer. The odds ratio was 3.2. Multiple logistic regression analysis showed that all severe events and coping with the stress of adverse events by confronting them and focusing on the problems significantly predicted a diagnosis of breast cancer. Non-severe life events and long term difficulties had no significant association. Conclusion: These findings suggest an aetiological association between life stress and breast cancer. 4A. What were the researchers interested in finding out (What is the exposure of interest? What is the health outcome of interest?)? 4B.What is the study design? Who are the cases? Who are the controls? 4C. What did they find, specifically? Interpret the odds ratio (or relative risk, as appropriate). 4D. What conclusions do the researchers draw from their findings? What do you think of their conclusions? 5. Why might the two studies have come to different conclusions? What might this difference in results say about the internal validity or external validity of each of these studies? Clearly, we don’t KNOW from viewing the abstracts, but, you should be able to come up with a reasonable explanation for this difference using the concepts of internal and/or external validity.
Explanation / Answer
3.
A. The study aims to find if there is any relation between stressful life events and onset on breast cancer , i.e. if stressful life events could be causing onset of breast cancer.
B. The setting is a case control study. The cases are the 399 women aged 40-79 and visiting the breast cancer clinic in Leeds and are residents of Leeds.
C. The study found that women diagnosed with breast cancer were no more likely to have experienced one or more severe life events or one or more severe difficulties than women diagnosed with a benign breast lump. The odds ratio is 1 for each.
D. The study found that there is no relation between onset of breast cancer and severed life events.
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