Joint Associations of Oxidative Stress, Central Obesity, and Cardiorespiratory Fitness with Diabetes and Pre-Diabetes: NHANES 1999-2004 Open Access

Gao, Jennifer (2016)

Permanent URL: https://etd.library.emory.edu/concern/etds/6969z108x?locale=en
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Abstract

PURPOSE: Obesity and central adiposity are well-known risk factors for cardiometabolic conditions including diabetes (DM), but little is known about the contribution of oxidative stress (OS) and cardiorespiratory fitness (CRF). This study will assess the individual and joint associations of central obesity, OS, and CRF with glycemic status using data from the National Health and Nutrition Examination Survey (NHANES) 1999-2004.

METHODS: This analysis was restricted to adults 20 years of age and older (n=12,662). We used polytomous logistic regression to assess the associations between waist-to-height ratio (WHtR) and oxidative stress score (OSS) with glycemic status outcomes (DM and pre-DM), adjusting for sociodemographics, family history of DM, modifiable risk factors, and co-morbidities. We conducted a sub-analysis (n=3,141; ages 20-49) of these associations with the addition of CRF as our third main exposure. Glycemic status was defined using self-reported diagnoses, use of insulin or other glucose-lowering medications, measured HbA1c, or fasting plasma glucose. OSS was calculated for each participant and divided into quartiles for the analyses using seven equally weighted biomarkers. WHtR ≥ 0.65 was used as a measure of central obesity. CRF was measured using submaximal treadmill testing, where the lowest 20th percentile of estimated VO2max represented low fitness.

RESULTS: 43.1% and 28.2% of adults with DM and pre-DM, respectively, had a WHtR ≥ 0.65. The mean OSS for those with DM and pre-DM was 1.01 and 0.45, respectively. An increased WHtR was significantly associated with pre-DM (OR=1.79, 95% CI: 1.52, 2.12) and DM (OR=3.42, 95% CI: 2.73, 4.29). The highest quartile of OSS was significantly associated with pre-DM (OR=2.34, 95% CI: 1.78, 3.07) and DM (OR=2.15, 95% CI: 1.53, 3.03). The sub-analysis showed that low CRF was significantly associated with pre-DM (OR=1.27, 95% CI: 1.07, 1.51) and DM (OR=2.86, 95% CI: 1.73, 4.70). The highest risk group (high central obesity, high OS, low CRF) had the strongest associations with pre-DM (OR=2.84; 95% CI: 2.51, 3.22) and DM (OR=7.57; 95% CI: 6.24, 9.19).

CONCLUSIONS: This study highlights the importance of central obesity, elevated OS, and low CRF in hyperglycemic individuals. These risk factors are all significantly associated with the odds of DM and pre-DM.

Table of Contents

CHAPTER I: BACKGROUND................................................................................................. 1

Diabetes Mellitus............................................................................................................... 1 Oxidative Stress and Diabetes.............................................................................................. 2 Waist-to-height ratio and Diabetes....................................................................................... 5 Cardiorespiratory Fitness..................................................................................................... 6 Problem Statement............................................................................................................. 8 Study Hypotheses.............................................................................................................. 9 Specific Aims..................................................................................................................... 9 CHAPTER II: METHODS...................................................................................................... 10 Study Design..................................................................................................................... 10 Study Population................................................................................................................ 11 Outcome Measures............................................................................................................. 11 Main Exposures.................................................................................................................. 12 Covariates........................................................................................................................ 15 Analytic Sample................................................................................................................. 17 Statistical Analysis............................................................................................................. 18 CHAPTER III: RESULTS...................................................................................................... 21 Future Directions............................................................................................................... 29 REFERENCES................................................................................................................... 31
Tables and Figures

Table 1.
Criteria used to define diabetes, pre-diabetes, and normoglycemia. Table 2. Characteristics of study participants by glycemic status, NHANES 1999-2004 population (n=12,662). Table 3. Main exposures of interest. Table 4. Partial correlation coefficients between exposure variables: OSS, WHtR, estimated VO2max. Table 5. Summary of bivariate associations between exposures and diabetes status. Table 6. Summary of bivariate associations between covariates and diabetes status. Table 7a. Summary of logistic regression output from candidate models for individuals with diabetes. Table 7b. Summary of logistic regression output from candidate models for individuals pre-diabetes. Table 8. Summary of variables included in each multivariate model (Models 0-5). Table 9a. Sub-analysis of associations between oxidative stress and diabetes among those with cardiovascular fitness data (n=3,141). Table 9b. Sub-analysis of associations between oxidative stress and pre-diabetes among those with cardiovascular fitness data (n=3,141). Table 10. Summary of variables included in each multivariate model (Models 0-5).
Figure 1.
Distribution of waist-to-height ratio in NHANES 1999-2004 population (n=12,662). Figure 2. Distribution of oxidative stress score in NHANES 1999-2004 population (n=12,662). Figure 3. Distribution of estimated VO2max in participants with valid cardiovascular fitness data in NHANES 1999-2004 (n=3,141). Figure 4. Selection of included survey participants (SP) from NHANES 1999-2004. Figure 5. Selection of included survey participants (SP) for sub-analysis with cardiovascular fitness data from NHANES 1999-2004. Figure 6. Joint Associations of Central Obesity, Oxidative Stress, and Cardiovascular Fitness with pre-DM and DM Figure 7. Directed acyclic graph (DAG) showing the associations between predictors and DM/pre-DM in this analysis (NHANES 1999-2004).

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