Does cardiorespiratory fitness modify the association between sitting time and health outcomes?
Prolonged sitting time is associated with numerous adverse health outcomes; however, the role of cardiorespiratory fitness (CRF) in these relationships is largely unexplored. The overall goal of this cross-sectional study is to explore the relationship between sedentary behavior and cardiovascular health indicators including CRF(paper 1) and cardiometabolic risk factors (paper 2), which, in turn, is critical for hypothesis generation to substantiate future research in this area. The study sample includes adult patients who presented to the Cooper Clinic (Dallas, Texas) for a preventive medical visit during 2010-2013 and who enrolled and consented to participate in the Cooper Center Longitudinal Study (CCLS). The specific aims are (1) To examine the cross-sectional association between sitting time and CRF (Paper 1); and (2) To examine the relationship between sitting time and cardiometabolic risk factors (Paper 2). In exploratory analyses, the potential role of CRF in the association between sitting time and cardiometabolic risk factors was also examined in Paper 2. In Paper 1, multiple linear regression analysis was employed to examine the association between sitting time and CRF adjusted for covariates for men and women separately. Among men, CRF was not associated with sitting time after adjustment for potential confounders. In contrast, for women, after adjustment, there was a significant association between increased sitting time and lower CRF. When the analytic sample was stratified by meeting or not meeting national physical activity (PA) guidelines, there was no association between sitting time and CRF in men. In women, this relationship was statistically significant regardless of whether or not PA guidelines were met. In Paper 2, multiple logistic regression models were constructed to assess the relationship between sitting time and cardiometabolic risk factors in men and women separately. In men, those who sat about 100% of the time were more than 2.5 times more likely to be obese whether defined by waist girth, BMI, or percent body fat as compared to men who sat approximately 0% of the time. Statistically significant associations between sitting time and each measure of adiposity were also found in women when adjusted for covariates. However, when CRF was added to the model, these associations no longer reached statistical significance. Sitting time was not significantly associated with detrimental levels of lipids, glucose, and blood pressure or the presence of metabolic syndrome in men or women after adjustment for CRF level. However, in exploratory analyses, the effect of sitting time on cardiometabolic risk factors appears to be mediated through cardiorespiratory fitness for women. In conclusion, few significant associations were found between sitting time and cardiovascular health indicators. In order to deepen our understanding of the importance of waking-time behaviors and cardiovascular health, future work is needed to not only replicate the findings in different populations, but to also confirm these findings in prospective studies that utilize more sophisticated measures of sitting time.^
Wright, Beth Barlow, "Does cardiorespiratory fitness modify the association between sitting time and health outcomes?" (2015). Texas Medical Center Dissertations (via ProQuest). AAI3720125.