Using Structural Equation Modeling to Examine the Effects of Sex and Physical Activity on the Metabolic Syndrome and Health-related Quality of Life Relationship

Using Structural Equation Modeling to Examine the Effects of Sex and Physical Activity on the Metabolic Syndrome and Health-related Quality of Life Relationship

Objectives: The purpose of this study was to use structural equation modeling (SEM) to investigate the moderating effects of sex and the mediating effects of physical activity (PA) on the metabolic syndrome (MetS) and health-related quality of life (HRQOL) relationship. Methods: The 2013-14 NHANES was used and included 1,077 adults 50+ years of age. A latent construct of MetS was created using five observed variables: waist circumference, HDL cholesterol, triglycerides, fasting glucose, and mean arterial pressure. A PA variable was created from self-reported moderate and vigorous recreational activity and converted to quartiles of moderate-to-vigorous PA minutes per week. HRQOL was assessed from a question regarding self-rated general health and dichotomized to indicate poor/good HRQOL. Results: The MetS latent model showed adequate fit (χ2/df = 2.47, GFI = 0.99, CFI = 0.99, and RMSEA = 0.04) and significantly (P<.001) predicted all observed variables. The structural model also showed adequate fit with significant direct effects of MetS on HRQOL (β= −0.118, P<0.001) and PA on HRQOL (β=0.176, P<0.001). The effect of MetS on HRQOL (β= −0.048, P=0.001) through PA revealed that PA mediates the relationship. The multi-group analysis showed that the structural model was significantly different between males and females, with PA completely mediating the MetS and HRQOL relationship in males and partially mediating the relationship in females. Conclusions: Results from this study support the use of SEM for investigating moderating and mediating effects while simultaneously measuring a latent construct. Additionally, PA was a stronger mediator to the MetS and HRQOL relationship in older males than in older females.