Aspects of energy intake assessment, dietary intake patterns and sleep duration in children

Abstract

Background A healthy balanced diet throughout childhood is an important determinant for health and wellbeing and is a key factor in prevention of overweight and several chronic diseases. Knowledge about children’s dietary habits is therefore an important public health issue, and valid and reliable dietary assessment methods for children are needed. Children’s dietary intake on weekdays and weekend days and the relationship between sleep duration and diet have only been sparsely investigated and further insight into these aspects may be valuable for further research and public health initiatives. Objectives The specific objectives of the present thesis were: (i) to evaluate energy intake (EI) estimated with a 2x24-hour recall method (2x24-HDRs) and the 7 day pre-coded food record (7-dFR) used in the Danish National Survey of Dietary Habits and Physical Activity 2003-2008 in children (Paper I); (ii) to compare children’s diet quality on weekdays (Monday-Thursday), Fridays and weekend days (Saturday-Sunday) (Paper II); (iii) to investigate children’s dietary intake patterns on weekdays and weekend days (Paper III); and (iv) to examine the relationship between sleep duration, BMI and food and nutrient intake in children (Paper IV). Methods EI estimated with 2x24-HDRs and the 7-dFR was evaluated by comparison with energy expenditure (EE) assessed using ActiReg® (PreMed AS, Oslo, Norway), a combined position and motion recording instrument. The study was conducted as part of the EFCOVAL (European Food Consumption Validation) study and included children in the age of 7-8 years (n=67) and 12-13 years (n=64). The analyses for Paper II-IV were based on data from the Danish National Survey of Dietary Habits and Physical Activity 2003-2008 and were conducted for the three age groups 4-6, 7-10 and 11-14 years. Diet quality was assessed by use of indicator variables and the unit g/10MJ, while dietary intake patterns were identified by use of Principal Component Analysis (n=784). The relationship between sleep duration, BMI and food and nutrient intake was assessed using Spearman’s correlation coefficient and multiple linear regression analysis (n=802). Results Compared to EE, EI was overestimated by 3% with the 2x24-HDRs (P=0.126) and underestimated by 7% with the 7-dFR (P=0.001) in the 7-8 year-old children. In the 12-13 year-old children, EI was underestimated by 10% with the 2x24-HDRs (P<0.001) and by 20% with the 7-dFR (P<0.001). The Pearson correlation coefficients between EI and EE were 0.48 for EI2x24-HDR and 0.32 for EI7-dFR in the 7-8 year-olds, and 0.48 for EI2x24-HDR and 0.37 for EI7-dFR in the 12-13 year-olds. The proportion of children classified in the same or adjacent quartiles was 76% for EI2x24-HDR and 73% for EI7-dFR in the 7-8 year-olds, and 83% for EI2x24-HDR and 70% for EI7-dFR in the 12-13 year-olds. For both genders in all three age groups, EI was consistently higher on weekend days than onweekdays. Moreover, intake of sugar-sweetened beverages and white bread was higher, whereasintake of rye bread was lower. This is in accordance with the findings of a higher percentage of energyfrom added sugars, a lower fibre content and a higher energy density of the diet on weekend days thanon weekdays. In children aged 4-6 and 7-10 years, the diet on weekend days was also characterised byhigher intakes of sweets and chocolate and lower intakes of fruit and vegetables (P<0.05). Overall, thediet on Fridays appeared as a mix of the diets on weekdays and weekend days. Two dietary patterns labelled “processed” and “health conscious” emerged consistently on both weekdays and weekenddays. Factor scores from corresponding dietary patterns were significantly correlated betweenweekdays and weekend days with exception of the “health conscious” pattern in the 7-10 year-olds.Children with high agreement for the “processed” pattern had a higher intake of sugar sweetenedbeverages, lower intakes of fruit and vegetables and a higher dietary energy density compared tochildren with high agreement for the “health conscious“ pattern (P<0.05). Moreover, these variablesindicated that the actual dietary intake on weekend days was less healthy compared to weekdays forboth patterns. Sleep duration and BMI was negatively correlated (P<0.001). In multiple linear regression analyses,sleep duration was not associated with energy intake (beta=-0.044, P=0.097), but solely with intake ofvegetables (beta=0.057, P=0.027), dietary fibre (beta=0.054, P=0.041) and liquid “empty calories” (beta=-0.055, P=0.035).  Conclusions  Misreporting of EI seemed modest at group level both with the 2x24-HDRs and the 7-dFR in the 7-8year-old children, whereas under-reporting appeared to be more evident in the 12-13 year-olds,especially with the 7-dFR. Overall, the 2x24-HDRs performed slightly better than the 7-dFR in terms ofranking of individuals according to EI. However, there are other aspects than EI that should be takeninto consideration in the overall evaluation of the two methods, for example that the higher EI with the2x24-HDRs mainly comprised higher intakes of healthy foods compared to the 7-dFR. Furtherdevelopments and refinements of dietary assessment methods are especially needed for older childrenand adolescents.  For both genders in the three age groups, average EI and energy density of the diet were consistentlyhigher on weekend days than on weekdays. The diet quality appeared to be lower on weekend dayscompared to weekdays and to be at an intermediate level on Fridays. The dietary pattern analysessuggest that children tend to maintain the same overall dietary patterns in weekdays and weekends,although the actual dietary intake is generally less healthy during weekends. These findings indicatethat more focus on the differences between weekdays and weekend days regarding EI and keyvariables, such as fruit and vegetables and foods high in added sugars, could prove useful forenhancing public health initiatives, especially regarding children with less healthy dietary patterns. Sleep duration was negatively correlated with BMI. However, sleep duration was not associated withenergy intake and the conception that children with short sleep duration have less healthy eatinghabits than children with longer sleep duration was only weakly supported by the present findings.More research is required to understand better the implications of chronic short sleep duration onappetite and energy balance, and whether strategies to improve sleep can influence appetite controland risk for weight gain.