Comparison of Objectively and Subjectively Measured Physical Activity and Its Association With Cardiovascular Risk Markers in South African School Children

Background
Cardiovascular diseases (CVDs) are the leading cause of death worldwide, accounting for one third of all global deaths. CVD prevention strategies should begin in early life since the onset of CVD is known to begin in childhood. The risk of CVD can be substantially reduced by focusing on lifestyle modifications. In particular, physical activity (PA) has received a lot of attention due to its beneficial effects on reducing the risk of CVD. An accurate and valid assessment of PA is required for studying its impact on health. Two commonly used assessment methods are questionnaires and motion sensors. However, the agreement between these methods is still a subject of discussion. This master’s thesis aims to compare self-reported PA with accelerometer-measured PA and to investigate its association with different cardiovascular risk markers (CRMs) in school children from South Africa.
Methods
Cross-sectional data of 594 (302 boys, 292 girls) South African school children between the ages of 8 – 13 years was included in the analysis. The data was collected as part of the KaziBantu project. PA was assessed subjectively using the Physical Activity Questionnaire for Older Children (PAQ-C) and objectively using ActiGraph wGT3X-BT accelerometers. Selected CRMs consisted of body mass index (BMI), blood pressure (BP), blood lipid profile (BLP), and glycated hemoglobin (HbA1c). Body height and weight was measured by stadiometer and digital weighing scale. Resting BP was measured with the Omron M6 AC blood pressure monitor. The Alere Afinion AS 100 Analyzer was used to determine the BLP and HbA1c concentrations.
Results
PAQ-C scores and accelerometer-measured minutes of moderate- to vigorous-intensity physical activity (MVPA) were positively associated (