v
TABLE OF CONTENTS
Acknowledgements iv
List of Tables vii
List of Figures viii
Chapter
1. Introduction 1
Cigarette Smoking as a Public Health Concern 1
Hypertension as a Public Health Concern 5
Purpose and Hypotheses 7
Gaps in Current Knowledge 9
2. Review of Literature 12
Evidence for the link between smoking and hypertension 12 Evidence for the interaction of smoking and hypertension 12 Evidence for inequalities in smoking and hypertension 13
3. Methods and Procedures 16
Data Source 16
Study Population 17
Outcome definitions 17
Potential Confounders 18
vi Statistical Analyses: Biostatistical Method 20 Statistical Analyses: Epidemiological Method 22
4. Results 24
Descriptive Characteristics 24
Hypothesis Testing 28
5. Discussion and Conclusion 48
6. References 52
7. Appendix: SAS Codes 59
vii
LIST OF TABLES
Table 1: Characteristics of the Study Population 25
Table 2: Mean of Continuous Variables 26
Table 3: Normality Check for Continuous Variables 26
Table 4: Collinearity Check for Continuous Variables 27
Table 5: Testing the Association of the Categorical Variables to the Dependent Variable 28 Table 6: Testing the Association of the Continuous Variables to the Dependent Variable 28
Table 7: Univariable Analyses 29
Table 8: Fitting a Preliminary Main Effects Model 29
Table 9: Results of the Fractional Polynomial Transformation 33
Table 10: Interactions Significant at the .05 level 34
Table 11: Fitting a Model Containing the Main Effects and Significant Interactions 34
Table 12: Results of Stepwise Regression 36
Table 13: Epidemiological Approach—Univariable Analyses 37
Table 14: Epidemiological Approach—Fitting a Preliminary Main Effects Model 38 Table 15: Fitting a Model Containing Main Effects and Significant Interaction Terms 39 Table 16: Epidemiological Approach Results of Stepwise Regression 40 Table 17: Epidemiological Approach—Assessing the Fit of the Model 41 Table 18: Epidemiological Approach—Final Model Interpretations 45
viii
LIST OF FIGURES
Figure 1: Smoothed Scatter plot of Patients Diagnosed vs. Age 30 Figure 2: Smoothed Scatter plot of Patients Diagnosed vs. Systolic Blood Pressure 30 Figure 3: Smoothed Scatter plot of Patients Diagnosed vs. BMI 31 Figure 4: Smoothed Scatter plot of Patients Diagnosed vs. Diastolic Blood Pressure 31 Figure 5: Smoothed Scatter plot of Patients Diagnosed vs. HDL cholesterol 32 Figure 6: Epidemiological Approach--Sensitivity vs. Probability Level Plot 42 Figure 7: Epidemiological Approach--ROC Curve (Sensitivity vs. 1-Specificity Plot) 43 Figure 8: Epidemiological Approach: Delta Chi-Square vs. Estimated Probability 43 Figure 9: Epidemiological Approach: Delta Deviance vs. Estimated Probability 44 Figure 10: Epidemiological Approach: Delta Beta Hat vs. Estimated Probability 44
