BIOST/STAT 578B – Data Analysis



BIOST/STAT 579

Chapter 1: Writing Scientific Papers

The Structure of a Scientific Paper

Abstract

Introduction – include statement of purpose

Methods – include description of study design

Results – primary results only

Conclusions

Introduction

Background & Significance

Previous Research – emphasize gaps in knowledge

Purpose

Methods

Study Design

Study Procedures (how you got the data)

Measures

Statistical Analysis

Results

“Descriptives” (use a specific, more descriptive, heading than this)

“Primary Analyses” (see above)

“Secondary Analyses” (see above)

Discussion

Conclusions

Implications

Limitations

Future Research

Acknowledgements - individuals, financial support

References

Appendices - highly technical material (but only include if needed and if cited in body of paper)

Structure of a Scientific Paper – Example 1

Source: Peterson AV Jr, Kealey KA, Mann SL, Marek PM, Sarason IG. Hutchinson Smoking Prevention Project: long-term randomized trial in school-based tobacco use prevention--results on smoking. J Natl Cancer Inst. 2000 Dec 20;92(24):1979-91

Abstract

Background

Methods

Results

Conclusion

Introduction

Subjects and Methods

Study Population and Sample Size

Randomized Assignment

Intervention

Implementation

Follow-up and Data Collection

Measures

Statistical Methods

Reporting the Design and Results of the Trial

Results

Baseline Comparability

Implementation Compliance

Follow-up/Data Acquisition Rates

Cotinine Validation of Self-Reported Tobacco Use

Results at Grade 12

Results at 2 Years After High School (Plus 2)

Results for a Priori-Hypothesized Subgroup Variables

Discussion

References

Notes

Structure of a Scientific Paper – Example 2

Source: Bauman KE, Foshee VA, Ennett ST, Pemberton M, Hicks KA, King TS, Koch GG. The influence of a family program on adolescent tobacco and alcohol use. Am J Public Health 2001 Apr;91(4):604-10.

Abstract

Objectives

Methods

Results

Conclusions

Introduction

Family Matters

Methods

Design, Sample, and Data Collection

Measures

Analyses

Sample Assessment

Results

Discussion

Conclusions

Contributors

Acknowledgements

References

Notes

Writing the Abstract

The abstract states the major purpose, methods and results.

Outline for an abstract (headings are optional):

Background: brief statement of significance, background, purpose or scientific question

Methods: study design, sample size, essential (eg, nonstandard) features of data collection and/or statistical analysis methods

Results: results for major scientific question(s) only

Discussion: implications, major limitations

Examples (Before class read these abstracts and decide what is good or bad about the highlighted sections)

Women's Healthy Lifestyle Project: A Randomized Clinical Trial : Results at 54 Months. Kuller LH, Simkin-Silverman LR, Wing RR, Meilahn EN, Ives DG. University of Pittsburgh, Departments of Epidemiology (L.H.K., L.R.S.-S., E.N.M., D.G.I.) and Psychiatry (R.R.W.), Pittsburgh, Pa. Circulation 2001 Jan 2;103(1):32-37.

BACKGROUND:-The Women's Healthy Lifestyle Project Clinical Trial tested the hypothesis that reducing saturated fat and cholesterol consumption and preventing weight gain by decreased caloric and fat intake and increased physical activity would prevent the rise in LDL cholesterol and weight gain in women during perimenopause to postmenopause. Methods and Results-There were 275 premenopausal women randomized into the assessment only group and 260 women into the intervention group. The mean age of participants at baseline was 47 years, and 92% of the women were white. The mean LDL cholesterol was 115 mg/dL at baseline, and mean body mass index was 25 kg/m(2). The follow-up through 54 months was excellent. By 54 months, 35% of the women had become postmenopausal. At the 54-month examination, there was a 3.5-mg/dL increase in LDL cholesterol in the intervention group and an 8.9-mg/dL increase in the assessment-only group (P:=0.009). Weight decreased 0.2 lb in the intervention and increased 5.2 lb in the assessment-only group (P:=0.000). Triglycerides and glucose also increased significantly more in the assessment-only group than in the intervention group. Waist circumference decreased 2.9 cm in the intervention compared with 0.5 cm in the assessment-only group (P:=0.000). CONCLUSIONS:-The trial was successful in reducing the rise in LDL cholesterol during perimenopause to postmenopause but could not completely eliminate the rise in LDL cholesterol. The trial was also successful in preventing the increase in weight from premenopause to perimenopause to postmenopause. The difference in LDL cholesterol between the assessment and intervention groups was most pronounced among postmenopausal women and occurred among hormone users and nonusers.

Example 2

A prospective study of physical activity and risk of prostate cancer in US physicians. Liu S, Lee IM, Linson P, Ajani U, Buring JE, Hennekens CH. Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02215, USA. Int J Epidemiol 2000 Feb;29(1):29-35

BACKGROUND: Exercise can suppress androgen production and may thus decrease the risk of prostate cancer. However, findings from epidemiological studies assessing physical activity and risk of prostate cancer are inconsistent. METHODS: We prospectively examined the association between physical activity and prostate cancer risk in the Physicians' Health Study (PHS), a randomized trial of low-dose aspirin and beta-carotene among 22,071 men aged 40-84 without self-reported myocardial infarction, stroke and cancer. At baseline in 1982, men were asked about the frequency of exercise vigorous enough to work up a sweat. Physical activity was assessed in a similar fashion again at 36 months of follow-up. RESULTS: During 11.1 years of follow-up (258 779 person-years), 982 cases of prostate cancer occurred and were confirmed by medical record review. After adjustment for potential confounding factors (including age, height, randomized treatment assignment, smoking status, alcohol intake, use of multivitamins, history of diabetes, history of hypertension and history of high cholesterol), the relative risks for prostate cancer associated with exercise vigorous enough to work up a sweat were 1.0 (referent) for frequency less than once per week, 1.02 (95% CI: 0.82-1.26) for once per week, 1.07 (95% CI: 0.90-1.27) for 2-4 times per week, and 1.11 (95% CI: 0.90-1.36) for 5+ times per week. Across all subgroups of men categorized by age, body mass index, smoking status, alcohol intake, use of multivitamins, history of diabetes, history of hypertension and history of high cholesterol, there were no significant associations between frequency of exercise vigorous enough to work up a sweat and prostate cancer risk. After excluding cases of prostate cancer that occurred during the first 36 months of follow-up, again, there was no significant association. Combining physical activity assessments at baseline and at 36 months also yielded no significant association with prostate cancer risk. CONCLUSIONS: These observational data from the Physicians' Health Study do not support the hypothesis that increased physical activity reduces the risk of prostate cancer.

Example 3:

Prevention of stroke in urban China: a community-based intervention trial. Fang XH, Kronmal RA, Li SC, Longstreth WT Jr, Cheng XM, Wang WZ, Wu S, Du XL, Siscovick D. Department of Neuroepidemiolology, Beijing Neurosurgical Institute, Beijing, People's Republic of China. Stroke 1999 Mar;30(3):495-501.

BACKGROUND AND PURPOSE: Stroke has been the second leading cause of death in large cities in China since the 1980s. Meanwhile, the prevalences of hypertension and smoking have steadily increased over the last 2 decades. Therefore, a community-based intervention trial was initiated in 7 Chinese cities in 1987. The overall goal of the study was to evaluate the effectiveness of an intervention aimed at reducing multiple risk factors for stroke. The primary study objective was to reduce the incidence of stroke by 25% over 3.5 years of intervention. METHODS: In May 1987 in each of 7 the cities, 2 geographically separated communities with a registered population of about 10 000 each were selected as either intervention or control communities. In each community, a cohort containing about 2700 subjects (>/=35 years old) free of stroke was sampled, and a survey was administered to obtain baseline data and screen the eligible subjects for intervention. In each city, a program of treatment for hypertension, heart disease, and diabetes was instituted in the intervention cohort (n approximately 2700) and health education was provided to the full intervention community (n approximately 10 000). A follow-up survey was conducted in 1990. Comparisons of intervention and control cohorts in each city were pooled to yield a single summary. RESULTS: A total of 18 786 subjects were recruited to the intervention cohort and 18 876 to the control cohort from 7 cities. After 3.5 years, 174 new stroke cases had occurred in the intervention cohort and 253 in the control cohort. The 3.5-year cumulative incidence of total stroke was significantly lower in the intervention cohort than the control cohort (0.93% versus 1.34%; RR=0.69; 95% CI, 0.57 to 0.84). The incidence rates of nonfatal and fatal stroke, as well as ischemic and hemorrhagic stroke, were significantly lower in the intervention cohort than the control cohort. The prevalence of hypertension increased by 4.3% in the intervention cohort and by 7.8% in the control cohort. The average systolic and diastolic blood pressures increased more in the control cohort than in the intervention cohort. Among hypertensive individuals in the intervention cohort, awareness of hypertension increased by 6.7% and the percentage of hypertensives who regularly took antihypertensive medication increased 13.2%. All of these indices became worse in the control cohort. The prevalence of heart diseases and diabetes increased significantly in the both cohorts (P ................
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