Epidemiology Presentation about

"Coffee consumption and pancreatic cancer"

Epidemiology

Prepared by :Sawsan fadwa

Kefaya itezaz

Fedaa walaa Ahmad shtaya

Presented to: Dr. Lina Khairy

Objectives

At the end of this interested discussion my colleges will be able to:

1. Answer on the related questions from Q1 –Q10 which includes:

2. Aim of the study and its hypothesis.

3. Study design questions.

4. Main exposure.

5. Main outcomes.

6. Confounding factors.

7. Data presentation and analysis.

8. Conclusions.

9. Recommendations to make this study better.

Q1. Aim of the study:

• The aim of this study is to access the relationship between coffee consumption, and pancreatic cancer, from the context, no clear statement for study purpose.

Q1. cont…

• While, the study hypothesis clearly stated in the abstract which is "no association with use of cigars, pipe, tobacco, alcoholic beverages, or tea, and a strong association between coffee consumption and pancreatic cancer was evident in both sexes, and week positive association between pancreatic cancer and cigarette smoking.

Q2. What was the study design?

• It is a case control study design.

A. Is the description of methods full and clear?

It was clear but not adequately full description for this method this appears in:

• When the researcher taken the patients with pancreatic cancer with histologic diagnosis, not obtained and reviewed.

Cont… Q2 A.

• The author don’t indicate whether the pts. Were newly diagnosed "incidence cases or prevalence cases".

• The interview, the author should explain the time, number of patients, place of interview, and characteristics of interviewer and numbers.

• Type of questionnaires not mintioned and it doesn’t in systematic way & without any evidence for questions about incidence and prevalence cases which lead to Information Bias.

Cont… Q2 A

• The way of control group selection – lead to Selection Bias, because when they select 273 pts with cancer other them pancreatic cancer such as stomach Ca. , of course these pts were stopped to consume coffee and cigarette smoking.

• There is no any information about exclusion people.

Q2. B.Do you know exactly what was done?

• According of design of the study, Cases and control groups selected according to specific criteria for these cases and controls, method of data collection were interview and stratification according to age and sex which have a bias in selection and information.

Cont…Q2. B.

• The analysis of data were with using measures of association, Bradford hill "criteria for causality" and statistically significant level and finally the author explained about this estimate which emphasizes the need to determine whether the association exists in other data and to evaluate it's causal or non causal nature.

Q2.C.Who were the study population:

Cases:• Were patients with a histologically confirmed diagnosis of

pancreatic cancer in 11 Boston & Rhode Island Hospitals from 1974 to 1979.

Controls:• Were selected from all patients who were hospitalized at the

same time as cases, and they were selected from other inpatients hospitalized by attending physicians who had hospitalized the cases and controls series composed of two principle diagnostic groups.

1. Pt. with cancer other than cancer in pancreas.

2. Pt. with other disorders.

• Main exposure was coffee consumption.

• In the study the coffee consumption and cigarette smoking are closely related to each other because (it is rare to find smoker who doesn’t drink coffee). And the data showed a consistent association of pancreatic Ca with coffee drinking with each category of smoking so that the main exposure in addition to coffee consumption is cigarette smoking.

Q3. A. what was the main exposure under investigation?

Q.3.B. how was it defined and measured in this study?

• It defined as "there is a strong association between coffee consumption and pancreatic cancer was evident in both sexes.

• It measured by asking the participant about the number of cups consumed per day, two cups, three or more cups.

Q.3 .C. Method of measurement – precision? Validity?

• This measurement was not précised or valid, because the interviewer could ask another question such as duration of coffee consumption rather than the numbers of cups as we know this was lead to information Bias.

Q4. A. what was the main out come under investigation?

Variable R.R Confidence interval

Adjusted interval

P-value

Tobacco 1.4 % 1.1 to 1.9 Men 1.4Women 1.5

(P~0.001)After

adjustment for cigarette smoking

Alcohol 0.9 0.6- 1.3 Men 1.3Women 0.8

Tea - Men 0.5 -1.1Women 0.5-1.2

Men 0.7Women o.7

coffee 2 cups 1.73 or more 2.7

Men 2.6Women 1.2-4.6

Men 2.6Women 2.3

P 0.001

Cont.. Q4. A

Conclusion:• Weak positive association between pancreatic

cancer and cigarette smoking.• No notable or significant association appeared

with drinking alcohol.• A slight inverse association appeared in both

sexes with drinking tea. • A strong association between coffee

consumption and pancreatic cancer.

B. how was it defined and measured in this study?

• It's defined as "A strong association between coffee consumption, weak positive association with smoking, and no association with alcohol and tea drinking".

It's measured with using:

• Relative Risk (odds ratio)

• Significant interval (P-value)

• Confidence interval

• Adjusted relative

• Mantel test to measure close- response relation for coffee.

• Chi-square, specially for coffee.

C. Method of measurement – precision? Validity?

• Yes, these methods and measurement were précised and valid because its statistics in nature which is strong and appropriate for study variables.

 

Q5. What possible confounding factors might there be? Were these

measured?

Exposure

Coffee consumptions

Confounder

Alchol

Smoking

Tea

Sex (men,women)

Age

Life style

Pancreatic cancer

Cont… Q 5

• Were these measured?

These confounders measured with using the method of mantel and Hansel and its extension (test of significance, estimates of adjusted relative risk) and their confidence limits except age, sex, life style.

Q 6. A. data presentation and analysis- how clear and complete?

• Descriptive characteristics of study population

Cases: were patients with histologic diagnosis of cancer of the exocrine pancreases.

• Not included (exclusion): • Pts. With tumor of islet cells.• Periampullary duodenal mucosa or ampula of vater.• Non white patient.• Residents of countries other than the United States.• Pts. Older than 79y.• Pts. whose interview information was judged by the interviewer to

be of questionable reliability.

Cont.. Q6.A.

• Controls: where the patient who were under the care of the same physician in the same hospital at the same time of an interview with pt. with pancreatic cancer, With two principal diagnostic group, pt with cancer other than cancer of the pancreas and biliary tract, respiratory tract, bladder. The control pt with cancer the tumer was in breast, colon, rectum, stomach, small intestine, ovary, prostate, cervix, and melanoma.

Cont.. Q6.A.

Exclusion criteria: in addition of disease of biliary tract or pancreas:

• cardiovascular disease

• Diabetes mellitus.

• Respiratory or bladder cancer.

• Peptic ulcer.

Unreliable pt. :

• Non white.

• Foreign residents.

• Older than 79y.

• 30 persons whose interviews.

Characteristics of control pts with other disorder:

• The principle diagnosis: hernia, colitis, enteritis, bowel obstruction, adhesion, fistula, gastritis.

• Other gastroenterologic conditions: benign tumors, varicose veins or phlebitis, genitourinary disorders, neurologic disorders, gynecologic disorders, and other conditions.

Q 6.B. complete presentation of numbers:

Cases No. Excluded from study

No.

identified 578 Non-white 8

interviewed 405 Residents of other countries

4

died 20 Pt. older than 79y 8

Discharged before interview

33 Whose interview information was

questionable reliability

16

Too sick 78

Language difficulties 14 Analysis based on data from the

remaining

369 pts.

Refused to interview 26

Two principal diagnostic groupsControls: No. 273-pt.with other

pancreas&biliary tract

No. 371-pt. with other disorder

No.

Eligible pt. 1118 Breast tumor 65 Hernia 70

interviewed 700 Colon 60 Colitis enteritis or diverticulities

41

Died 9 Rectum 25 Bowel obstruction,adhesion,fi

stula

26

Discharged before

interview

131 Stomach 24 gastritis 17

Too ill 179 Small intestine 9 Other gastroenterologic

47

Language problems

26 Ovary 8 Benign tumor 29

refused 73 Prostate 8 Varicose vein,phlebities

21Cervix 7 Genitourinary disorder 20

Melanoma 16 Neurological disorder 20

Lymphoma 15 Gyrecologic disorders 16

 Other conditions 64

Cont.. Q6 B

Exclusions No.

Non-white 17

Foreign resident 5

Older than 79y 4

Whose interview un reliable 30

The analysis consisted of 644 pt.The analysis consisted of 644 pt.

The analysis consisted of 644 pts

 

Q6. C. measure if association and risk:

• Data presentation and analysis with using measures of association and risk (R.R, adjusted relative risk, confidence interval and statistically significance, mantel test, chi-square) all of these measure were clear and complete.

Q6. D. Statistical significance:

• Calculated for cigarette smoking after adjustment for cigarette smoking (P~ 0.001), and for coffee consumption (P 0.001) for sexes combined with simultaneous adjustment for sex & age.

Q6. E.Control for confounders and bias:

• Control for cofounders not complete because the researcher control the confounder by using stratification and statistical modeling in the analysis while in the design no any of randomization, restriction, and matching used.

Cont… Q6.E.

 

• While the Bias This study has many types of Bias such as the first one Selection Bias, and information Bias, exclusion and inclusion Bias, death bias, all of these biases not controlled well.

Q 7. Could the observation observed be due to

• The association in this study due to:

I. Chance: when a multiple characteristics of two groups are test for "statistically significant" differences, one or more of those characteristics may seem "significant by chance".

II.Bias: • selection, appear during control selection because the

pt. with control group with cancer has a stomach cancer these pt. may decrease or stopped taking coffee and cigarette smoking due to their illness.

Cont.. Q7

• .Information, due to incomplete the quality and quantity of information about the exposure especially coffee consuming.

• And the association due to confounding because the researcher not controlled completely on the confounder, such as matching, restriction, and randomization.

• And this association due to cause (dose- response relation) the author reported that there was a significant dose- response relation (P~ 0.001) after adjustment for cigarette smoking.

Q8. A. Conclusions

• How do the findings relate to the aims / study hypothesis?

1.About the alcohol: "it seems unlikely that alcohol consumption has any role in the origin of cancer of pancreas because this substance cause in chronic pancreatitis this approved in study hypothesis when the author said that no association between alcohol and pancreatic cancer.

Cont… Conclusions2. There is a small excess of men with the disease in

proportion to women would seem to be more suggestion of a role of coffee rather than for cigarettes. This appears and explained that there is a weak positive association between cigarette smoking and pancreatic cancer.

3. The author estimate the proportion of pancreatic cancer that is potentially attributable to coffee consumption to be slightly more their 50%, this percentage explained as reported in study hypothesis there is a positive association between pancreatic cancer & coffee consumption but need more emphasizes to evaluate its causal and uncausal nature.

Q8. B. How genaralizable do you thinks the variables are?

• In this study the variables couldn’t generalized due to presence of several types of bias and this study need more emphasizes the need to determine whether the association exists in other data and to evaluate its causal or non causal nature, so that variables couldn’t generalized.

Q8. C. is the interpretation of results, and hence, the conclusions justified?

• Yes, it's for example when the interpretation of coffee consumption in table No. -4-

men Women

Adjusted relative risk

2.6 2.3

Confidence interval 1.2-5.4 1.2-4.6

Table conclusion

• Conclusion: small excess of men with the disease in proportion to women would seem to be more suggestion of a role for coffee rather than for cigarettes.

Q9. Abstract: does this clearly and fairly summarized what is shown in the paper?

• No, it doesn’t, the abstract of this study summarize the number of study population and the conclusions while the abstract should include more details about the study.

Q10. How would you do this study better?

1. Make randomization especially for control group "people without pancreatic cancer would be assigned either to drink or not to drink coffee to decrease the bias.

2. Control the confounder by applying the matching & restriction of cases and controls.

3. The patient with GI disorder should not select either case or control.

4. Eliminate gender and coffee qualifications.

5. The investigator should perform detailed analysis to show that the remaining pts not affect the results due to bias.