Date of Award

Summer 2019

Document Type

Open Access Thesis


Epidemiology and Biostatistics

First Advisor

Michael D. Wirth

Second Advisor

Andrew Ortaglia


OBJECTIVE: This study examined the relationship between cardiorespiratory fitness (CRF) and age to determine if the decrease in CRF associated with advancing age is greater among those with type 2 diabetes mellitus (T2DM) as compared to those without T2DM. This study also assessed if differences in CRF between persons with T2DM and those without are consistent across CRF percentiles.

METHODS: Data from the Aerobics Center Longitudinal Study (ACLS, Dallas, Texas, 1970-2006) were utilized in the current study. CRF was measured by maximal treadmill exercise testing using the Balke protocol and T2DM status was determined by self-report of previous diagnosis by a physician, a fasting glucose of >126 mg/dL, or insulin use. Multivariable linear regression was performed to assess the association between CRF and age taking into account the interaction between T2DM status and age and adjusting for potential confounding variables. Additionally, quantile regression was performed to estimate the association between the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles of CRF and T2DM status.

RESULTS: The 12,648 predominantly non-Hispanic white, well-educated, and middle-toupper socio-economic status men included in the sample with an average of 3.63 visits resulted in 49,704 complete observations (568 from those with T2DM). In the linear regression analyses, the interaction between T2DM status and age was statistically significant. For those with T2DM, the decrease in CRF is an additional 0.020 METs per one-year increment of age as compared to those without T2DM. Across the 5th, 10th, 25th, 50th, and 75th percentiles of CRF, diabetics had significantly lower CRF (-0.594, -0.456, -0.464, -0.333, -0.207 respectively) compared to non-diabetics.

CONCLUSIONS: This study show that the decrease in CRF associated with age was greater those with T2DM compared to those without T2DM. Through understanding the relationship between CRF and advancing age for those with and without T2DM, as well as understanding the differences between T2DM and CRF across the entire distribution of CRF, we can better tailor physical fitness interventions for populations looking to reduce the occurrence of diseases known to be associated with CRF.


© 2019, Amber Kathlyn Watson

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