Cardiometabolic risk factors in children: reference values, association with cardiorespiratory fitness and effects of the Active Smarter Kids (ASK) physical activity intervention

Abstract

Cardiovascular disease (CVD) is the leading cause of disease-related morbidity and global mortality among adults (1, 2). In children, a clinical manifestation of CVD is not present, but studies have shown that atherosclerosis originates during childhood (3-7). In addition, studies suggest that individual CVD (or cardiometabolic) risk factors, such as obesity (8), blood pressure (BP) (9), and lipids/lipoproteins (10) as well as the clustering of these risk factors (11-14), may track from childhood to adulthood, conveying increased risk of CVDs and type 2 diabetes. Thus, monitoring, surveillance and profiling of clustered cardiometabolic risk in children, as well as the development of effective prevention and health promotion strategies, is important from a public health perspective. The term metabolic syndrome refers to clustering of cardiometabolic risk factors and is diagnosed when individuals’ exhibit elevated levels in three or more risk factors above certain thresholds (15-18). However, no consensus exits as to which exact risk factors and thresholds should be used to define the metabolic syndrome (15-21). Furthermore, dichotomization of risk variables ignores that cardiometabolic risk likely is a continuum and substantially decreases the amount of available information, therefore also the power of statistical analysis (22-24). In addition, since children do not have established CVDs, makes the argument to use thresholds in children even more unsustainable. Thus, the use of continuous clustered risk scores is arguably superior to dichotomized versions, especially in the pediatric population. From this perspective, international reference values is highly warranted to offer a common standard for defining levels of cardiometabolic risk in children and adolescents, when using continuous clustered risk scores. Physical inactivity and low cardiorespiratory fitness (CRF) are major causes of the cardiometabolic health burdens worldwide (25, 26). The school has been emphasized as an ideal environment for public health interventions by the World Health Organization (WHO) among others (27, 28), since children spend a substantial fraction of their waking hours in school. Furthermore, as an institution, the school has the means to reach most children irrespective of socioeconomic status or parents’ attitude and behavior regarding PA.

The aim of this thesis was threefold. The first aim was to produce international reference values for cardiometabolic risk variables in children and adolescents. The second aim was to investigate and compare cardiometabolic risk levels in 10-year-old Norwegian children from the Active Smarter Kids (ASK) study to the international reference values and examine the association between CRF and the reference-standardized clustered risk score. The third aim was to investigate the effect of the ASK study’s school-based PA intervention on single and clustered cardiometabolic risk in children.

Paper I: Stavnsbo, Mette; Resaland, Geir Kåre; Anderssen, Sigmund Alfred; Steene-Johannessen, Jostein; Domazet, Sidsel Louise; Skrede, Turid; Sardinha, Luis B.; Kriemler, Susi; Ekelund, Ulf; Andersen, Lars Bo; Aadland, Eivind. Reference values for cardiometabolic risk scores in children and adolescents: Suggesting a common standard. Atherosclerosis 2018 ;Volum 278, s.299-306

Paper II: Stavnsbo, Mette; Skrede, Turid; Aadland, Eivind; Aadland, Katrine Nyvoll; Chinapaw, Mai; Anderssen, Sigmund Alfred; Andersen, Lars Bo; Resaland, Geir Kåre. Cardiometabolic risk factor levels in Norwegian children compared to international reference values: The ASK study. PLOS ONE 2019 ;Volum 14.(8)

Paper III: Stavnsbo, Mette; Aadland, Eivind; Anderssen, Sigmund Alfred; Chinapaw, Mai; Steene-Johannessen, Jostein; Andersen, Lars Bo; Resaland, Geir Kåre. Effects of the Active Smarter Kids (ASK) physical activity intervention on cardiometabolic risk factors in children: A cluster-randomized controlled trial. Preventive Medicine 2019 ;Volum 130.