The relationship between physical activity and markers of the metabolic syndrome in adolescents : the PAHL-study

Abstract

Low levels of physical activity (PA) are associated with a dramatic rise in obesity. The increase in prevalence of overweight and obesity is in parallel with an increase in metabolic syndrome (MetS) prevalence. Numerous studies have documented decreasing levels of PA together with an increase in overweight and obesity in South African adolescents. Few studies which could be found indicated that the prevalence of MetS in adolescents is high. Information on the prevalence of MetS and how it relates to PA levels in South African adolescents is scanty. It was therefore appropriate to use data from Physical Activity and Health Longitudinal Study (PAHLS) with the overarching aim of describing the development of PA and the determinants of health risk factors in 14-18 year-old adolescents longitudinally to answer the following questions. Firstly, what is the prevalence of MetS in adolescents residing in the Tlokwe Municipality of the North West Province? Secondly, what is the relationship between PA levels and the MetS markers of adolescents in the Tlokwe Municipality of the North West Province? Adolescents from six high schools from both high and low socioeconomic areas were recruited to take part in the study. A total of 215 adolescents aged 15 years gave consent for blood sampling and of those, a 188 completed the PA questionnaire using the short form of the International Physical Activity Questionnaire (IPAQ-S). The following variables; body mass, stature, waist and hip circumference, glucose, high density lipoprotein, triglycerides and blood pressure were determined according to standard procedures. PA measures were categorised as follows; vigorous PA, walk PA and total PA as metabolic equivalents minutes per week (MET min/week). Daily moderate to vigorous physical activity (MVPA) was also computed to classify adolescents as either meeting the PA guidelines or not meeting the guidelines of ≥60 min/day of MVPA. Data was analysed with SPSS IBM software version 22. Descriptive statistics were computed to give participants characteristics in terms of means and standard deviations as well as median and interquartile range for PA parameters. Spearman (rho) correlation was performed to determine the relationship between PA levels and MetS markers. Odds ratios were calculated to establish the level of risks for being classified as having the MetS in terms of not meeting recommended 60 min/day MVPA versus persons meeting the recommended MVPA guidelines. The results indicate that only 25% of the adolescent included in the study met the recommended PA guidelines. The findings also indicate that the prevalence of MetS is 2.3% and 5.6% with IDF and NCEP/ATP III criteria respectively. Prevalence of MetS is significantly higher in the overweight compared to the normal weight (p<0.05) participants. The results further revealed that 7.9% and 22.9% (IDF and NCEP criteria respectively) of the adolescents presented with two or more of the risk factors of MetS. Vigorous PA was reported to be inversely associated with DBP (r=-0.14; p=0.05). No significant relationship was noted between PA measures and the other markers of MetS. The odds of being diagnosed with MetS when applying the NCEP/ATP III criteria when not meeting recommended PA guidelines is 2.4 times higher than when meeting the PA guidelines. No clear relationship was noted when MetS was diagnosed with the IDF criteria. These findings were however not significant with either diagnostic criteria. Adolescents aged 15 years in Tlokwe Municipality of the North West Province are not adequately active and this inactivity possibly contributes to the overweight observed and associated high prevalence of MetS. An increase in PA might reduce the risk of MetS via the mechanism that reduces blood pressure.