| Summary: | Introduction:
Obesity plays an important role in the development of the metabolic syndrome, with central obesity being included as a required prerequisite in the most recent definition of the metabolic syndrome by the International Diabetes Federation (IDF). The following components were included in the Joint Statement Consensus (JSC) definition: raised blood pressure (systolic BP ? 130 or diastolic BP ? 85 mm Hg), raised triglycerides (Trig)( ? 1.7 mmol/L) and lowered high–density lipoprotein cholesterol (HDL)(< 1.03 mmol/L in males and < 1.29 mmol/L in females), raised fasting glucose (? 5.6 mmol/L), and central obesity. Population– and country–specific definitions for waist circumference is recommended, although the IDF cut points are to be used for non–Europeans until more data are available.
Aim:
Consequently, the aim of the study was to determine a population–specific waist circumference (WC) cut off, comparing the new proposed waist circumference model (NPM) with the current cut offs proposed by the Joint Statement Consensus (JSC). Association between the new proposed cut off and perception of own health in a group of urban African teachers was also investigated.
Method:
WC, sphygmomanometer blood pressure, fasting bloods (glucose, HDL and triglycerides) and ultrasound carotid intima–media thickness (CIMT) were obtained for 171 black urban teachers from the sympathetic activity and ambulatory blood pressure in Africans (SABPA) study. Perception of own health was determined via the General Health Questionnaire–28 (GHQ–28). Gender–separate receiver operating curve (ROC) analyses were performed for each of the metabolic syndrome components to determine a new population–specific waist circumference cut off. Subsequently Logistic Regression and Neural Networks analyses were performed in order to validate the NPM. Thereafter the association between the NPM and perception of own health was considered.
Results:
The respective blood pressure cut offs corresponded best with WC pathology, and a NPM was proposed with the new WC cut off for the males be set at 90 cm as opposed to the current 94 cm; whilst the female cut off be set at 98 cm as opposed to the existing cut off of 80 cm. Thereafter ROC analyses (not adjusting for covariates), Logistic Regression and Neural Networks statistics (both adjusting for a priori confounders, age, BMI and physical activity) validated that the NPM model was comparable to the JSC model. Both models correlated with CIMT, an indicator of structural vascular disease. When comparing the JSC and NPM WC models, only the NPM model was associated with perception of own poorer health.
Conclusion:
A new population and ethnicity–specific WC cut off was recommended (NPM). Subsequently the NPM was validated via Logistic Regression and Neural Networks statistical analyses. The NPM was comparable with the JSC cut offs which are currently in use in predicting structural vascular disease via CIMT. It is proposed that the NPM cut offs be used in this population due to the strong association between blood pressure and the proposed WC cut offs, validated by Logistic Regression and Neural Networks statistical analyses. Furthermore, associations were demonstrated between the NPM and perception of own health in a group of urban Africans. === Thesis (PhD (Human Movement Science))--North-West University, Potchefstroom Campus, 2012.
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