Date of Award

8-2014

Degree Name

Doctor of Philosophy in Nursing (PhD)

Advisor(s)

Janet C. Meininger

Second Advisor

Duck-Hee Kang

Third Advisor

Kelley P. Gabriel

Abstract

Background: Low grade systemic inflammation plays a key role in atherosclerosis, and C-reactive protein (hs-CRP), interleukin-6 (IL-6), and tumor necrosis factor- alpha (TNF -a), markers of systemic inflammation, are associated with cardiovascular events and adiposity. Cardiorespiratory fitness has shown health benefits by reducing circulating levels of inflammatory markers. However, it remains uncertain whether the negative association between cardiorespiratory fitness and inflammatory biomarkers is due to cardiorespiratory fitness itself or results from lower levels of adiposity. Moreover, the evidence examining the interaction between cardiorespiratory fitness and adiposity in inflammation in young adults is lacking.

Purpose: The aims of this study were to (1) determine the strength of the associations of cardiorespiratory fitness and adiposity (body mass index [BMI], waist circumference [WC]) with circulating levels of plasma hs-CRP, IL-6, and TNF-a; and (2) test the moderating effect of adiposity on the strength of the association between cardiorespiratory fitness and circulating levels of plasma hs-CRP, IL-6, and TNF -a.

Methods A cross-sectional study was conducted with 88 young adults aged 20-34 years without diagnosed diseases. A submaximal treadmill walking test was used to assess v cardiorespiratory fitness. BMI and WC were measured to assess adiposity. The hs-CRP, IL-6 and TNF-a were assayed and were log10-transformed. For aim one, a separate multiple regression analysis was conducted with each ofhs-CRP, IL-6, and TNF-a as dependent variables and adjusted for confounders. Analysis of covariance (ANCOVA) was used and adjusted for confounders for aim two. Confounding variables tested were sex, ethnicity, oral contraceptive use, and education level.

Results Aiml: Cardiorespiratory fitness was not significantly associated with log1ohs-CRP after adjustment for BMI or WC and confounders. Cardiorespiratory fitness was not significantly associated with log10IL-6 after adjustment for BMI and confounders. However, cardiorespiratory fitness was significantly and negatively associated with log10IL-6 after adjustment for WC and confounders (Model adjusted R2 =.273,p < .0001; p = -.341, t = -1.995,p =.049). Aim 2: Cardiorespiratory fitness X BMI or we interaction was not significantly associated with log10hs-CRP after adjustment for confounders. Similarly, cardiorespiratory fitness x BMI interaction was not significantly associated with log10IL-6 after adjustment for confounders. However, cardiorespiratory fitness x WC interaction was significantly associated with log10IL-6 after adjustment for confounders (Model adjusted R2 = .258,p < .0001; partial eta2 =.056, F = 4.730,p = .033). There were no associations of cardiorespiratory fitness, adiposity, and log10 TNF-a.

Conclusions: In young adults, higher cardiorespiratory fitness is significantly associated with lower levels of IL-6, particularly in young adults with central adiposity. Further studies are warranted to determine if experimentally induced increases in cardiorespiratory fitness Vl reduce inflammatory markers in young adults. Longitudinal studies are needed to understand the underlying inflammatory mechanisms related to interaction between cardiorespiratory fitness and adiposity, and its influence on cardiovascular disease risk in young adults.

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Nursing Commons

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