Scientific writing (81-933) Lecture 5: Discussion Dr. Avraham Samson Faculty of Medicine in the Galilee 1

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THE DISCUSSION The Discussion is the section that… Gives you the most freedom Gives you the most chance to put good writing on display Is the most challenging to write

The Discussion The purpose of the discussion: Answer the question posed in the Introduction Support your conclusion with details (yours, others) Defend your conclusion (acknowledge limits, caveats) Highlight the broader implications of the work (i.e., What do my results mean and why should anyone care?) Future plans (optional). Strong conclusion

The Discussion The introduction moves from general to specific. The discussion moves from specific to general.

The Discussion Things to avoid in the discussion: Do not simply repeat what is in the Results Do not try to explain every minor flaw Do not attempt to explain away every unexpected result Do not exaggerate or make extravagant claims Dont hedge

What NOT to do! Dont start your discussion like this!! Discussion This meta-analysis is subject to a number of limitations. The estimates of risk for melanoma subsequent to using sunlamps/sunbeds are based on published data in a series of 10 articles over a period of 20 years. A pooled analysis of original observations taken in the 10 studies would have provided a more powerful approach …

The Discussion: verb tense Verb Tenses (active!): Past, when referring to study details, results, analyses, and background research: We found that They lost more weight than Subjects may have experienced Miller et al. found Present, when talking about what the data suggest … The greater weight loss suggests The explanation for this difference is not clear. Potential explanations include

EXAMPLE: Adherence to Mediterranean diet and risk of developing diabetes: prospective cohort study BMJ June 2008 END OF INTRODUCTION: We evaluated the association between adherence to a Mediterranean diet and the incidence of diabetes using a full validated food frequency questionnaire to measure the entire diet.

The Discussion 1. This large prospective study shows that a traditional Mediterranean food pattern is associated with a significant reduction in the risk of developing type 2 diabetes. [answer to question asked]

The Discussion 2. Interestingly, among participants with the highest adherence to the diet, there was a high prevalence of important risk factors for diabetes, such as older age, higher BMI, family history of diabetes, and personal history of hypertension and a higher proportion of ex- smokers. Therefore, we would have expected a higher incidence of diabetes among these participants. These higher risk participants with better adherence to the diet, however, had a lower risk of diabetes, suggesting that the diet might have a substantial potential for prevention. [bonus finding/additional evidence] This finding is consistent with our previous report of an inverse association between a Mediterranean diet and the metabolic syndrome.24 [fits with previous research] The metabolic syndrome is closely associated with a generalised metabolic disorder of insulin resistance, which is one of the underlying causes of type 2 diabetes. Therefore a high biological plausibility exists to support the causality of our findings. [biological mechanisms] In addition, a previous cohort study of survivors of myocardial infarction also reported that a higher adherence to a Mediterranean diet was associated with a reduction in the risk of type 2 diabetes,18 [fits previous research] despite use of a relatively inaccurate tool for the dietary assessment. The inverse graded dose-response pattern and the significant inverse trend that we observed also support a causal relation. [dose-response evidence]2418

The Discussion 3. Diet and disease.Experimental evidence suggesting that a diet similar to the Mediterranean diet and rich in plant based foods might protect against diabetes can also be found in the Indian diabetes prevention programme. That trial promoted a plant based diet (together with increases in physical activity) and found a significant reduction in the incidence of diabetes,28 although there are clear differences between the Mediterranean and Indian food patterns. There is an analogy between coronary heart disease and diabetes because patients with type 2 diabetes and no coronary heart disease have a risk of coronary heart disease similar to patients without diabetes but with prior coronary heart disease.29 There is evidence that a Mediterranean diet protects against coronary heart disease, and the analogy between coronary heart disease and diabetes suggests that this diet might also prevent diabetes. It has been shown to provide protection against coronary mortality and the incidence of non-fatal myocardial infarction.32 In addition, both cohort studies and randomised trials36 have found that adherence to a Mediterranean diet protects against mortality in patients who already have established coronary heart disease. [more supporting background evidence]

The Discussion Limitations. The number of new cases of diabetes was small, despite the follow-up of several thousand people for over four years. This small number of incident cases is a major drawback and can compromise the statistical power of our study. Nevertheless, our participants had high absolute levels of consumption of the typical food items of the Mediterranean diet, even among those participants classified as poorly compliant (score <3). For example, among those in the lowest category of adherence to the diet, the estimated mean daily absolute consumption (g/day) of olive oil (12), vegetables (308), fruits (176), cereals (77), and legumes (17) can be considered as healthy for the standards of nutritional epidemiological studies. This high consumption of plant based foods in our cohort could be because our participants were from a Mediterranean country and were highly educated and health conscious. The small number of new cases observed in this study should therefore not be surprising. If the Mediterranean diet is actually protecting against diabetes, we would expecta low incidence in a young cohort (mean age is 37.8 years) with these characteristics. The low number of observed cases precluded assessment of the specific role of single dietary factors because we would have needed [Limitations]

The Discussion Conclusion. Our prospective cohort study suggests that substantial protection against diabetes can be obtained with the traditional Mediterranean diet, rich in olive oil, vegetables, fruits, nuts, cereals, legumes, and fish but relatively low in meat and dairy products. The limited number of cases of diabetes and the possibility of under-reporting, however, requires that further larger cohorts and trials are needed to confirm our findings. [Restatement of the findingstake home message]

1.The answer to the key question asked 2.Whats new 3.The context. How your results fit into, contradict, or add to whats known or believed 4.Strengths and limits of the study 5.Overall conclusion Discussion

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Subject verb object

Right! The Neanderthal man became extinct 30,000 year ago. Recently however, Neanderthal genes were found in living humans. In addition, Neanderthal features such as long noses and light hair are commonly observed in todays population. These findings suggest that Neanderthals intermarried with Homo Sapiens. 18

Wrong! 30,000 years ago, the Neanderthal man was extincted. In living human, genes of Neanderthals were found. Also, Neanderthal features such as long nose and light hair are commonly observed in todays population. Homo Sapiens and Neanderthals can intermarry. 19

Principles of Effective Writing The fear expressed by some teachers that students would not learn statistics well if they were permitted to use canned computer programs has not been realized in our experience. A careful monitoring of achievement levels before and after the introduction of computers in the teaching of our course revealed no appreciable change in students performances. Really long subject! negatives Passive voice wordy

Principles of Effective Writing The fear expressed by some teachers that students would not learn statistics well if they were permitted to use canned computer programs has not been realized in our experience. A careful monitoring of achievement levels before and after the introduction of computers in the teaching of our course revealed no appreciable change in students performances. Really long subject! Buried predicate + boring verb hedge word

Principles of Effective Writing Many teachers feared that the use of canned computer programs would prevent students from learning statistics. We monitored student achievement levels before and after the introduction of computers in our course and found no detriments in performance.

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1. Peremptory v. preemptive Peremptory = cannot be denied Preemptive = action is one taken before an adversary can act He issued a peremptory order. He ordered a preemptive war in Iraq.

2. Subject v. patient A subject is a volunteer. A patient is under treatment by a doctor. The subjects in our study took a quiz about love. The patients in our study were being treated for their stomach conditions. Alternatives to subject: participants, volunteers, men, women, postmenopausal women, runners, smokers, etc.

3. Strata v. stratum Strata is plural. Stratum is singular. We analyzed the data, adjusting for the different age strata. I was only interested in the association in the stratum of elderly subjects.

4. Nucleus v. nuclei Nuclei is plural. Nucleus is singular. The cell nucleus displayed a pattern of chromosome abnormalities. Proton nuclei in different chemical environments display distinct precession frequencies 28

5. Averse v. adverse Averse means opposed and usually describes a persons attitude. Adverse means hostile, unfavorable, opposed but usually applies to situations, conditions, or eventsnot people. The bad weather has an adverse effect on my car. I would not be averse to trying that new restaurant.

6. Historic v. historical Historic means notable in history. --indicates that it in some way changed the course of human events Historical means relating to history or past events. --not necessarily historic The signing of the Declaration of Independence was a historic moment in American history. Professor Smith gave a historical lecture on the evolution of toothpicks.

7. Ultimate and Penultimate Ultimate: last (from Latin, ultimare=come to an end) Penultimate: second to last (paene=almost; ultimas=last) The ultimate aim was to force his resignation. The character was arrested in the penultimate chapter, setting up the central tension of the final chapter.

32 July 2, 2001 Re: Letter Of Reference To: John Doe To Whom It May Concern: Bob Smith, my assistant programmer, can always be found hard at work in his cubicle. Bob works independently, without wasting company time talking to colleagues. Bob never thinks twice about assisting fellow employees, and he always finishes given assignments on time. Often he takes extended measures to complete his work, sometimes skipping coffee breaks. Bob is a dedicated individual who has absolutely no vanity, in spite of his high accomplishments and profound knowledge in his field. I firmly believe that Bob can be classed as a high-caliber employee, the type which cannot be dispensed with. Consequently, I duly recommend that Bob be promoted to executive management, and a proposal will be executed as soon as possible. Received a short time later: Re: Letter Of Reference To: John Doe Mr. Doe: That idiot was standing over my shoulder while I wrote the letter I sent to you earlier today. Kindly re-read only every other line.