Friday, November 7, 2014

Personal, home- and friend-related factors regarding diet, physical activity and sedentary behaviours among schoolchildren in Europe

To design interventions that target energy balance-related behaviours -i.e. diet, physical activities (PA) and sedentary behaviours- among school-age children, knowledge the possible determinants of these behaviours is needed. In a study just published in PLOS ONE -with Dr. Saskia te Velde as first author- we investigated schoolchildren's  personal beliefs and attitudes, home- and friend-related variables regarding soft drink intake, fruit juice intake, breakfast consumption, TV viewing and physical activity in eight countries across Europe. This study was part of the ENERGY project.
A majority of the children reported unfavourable attitudes, preferences and subjective norms regarding soft drink, fruit juice intake and TV viewing accompanied with high availability and accessibility at home. Few children reported unfavourable attitudes and preferences regarding breakfast consumption and PA. Many children reported unfavourable health beliefs regarding breakfast consumption and TV viewing. Substantial differences between countries were observed, especially for variables regarding soft drink intake, breakfast consumption and TV viewing.
We concluded that children across Europe have favourable attitudes to some healthy behaviours (PA, breakfast intake) as well as to some unhealthy behaviours (soft drink consumption, TV viewing). Additionally, many children across Europe have personal beliefs and are exposed to social environments that are not supportive to engagement in healthy behaviours. Moreover, the large differences in personal, family and friend-related variables across Europe argue for implementing different intervention strategies in the different European countries.

Patterns in sedentary behaviour: data reduction issues

Sedentary behaviour may be another risk factor for obesity and cardiometabolic risk. Sedentary lipoprotein lipase activity, leading to a prolonged time in which cellular metabolism substrates are present in the vascular compartments.
behaviour is not the same as the opposite of lack of physical exercise: even people who have enough exercise may sit too much during the rest of the day. Recent evidence suggest that it may be prolonged, uninterrupted sitting -rather than total sitting time- that may increase cardiometabolic risk. Prolonged sitting leads to the loss of contractile stimulation in weight-bearing muscles, which suppresses skeletal muscle
However, measuring sitting time and sedentary patterns is not as straightforward as it may seem. Sedentary behaviour is maybe best measured with accelerometers, however, no consensus is yet established on such accelerometer data most validly reflect sedentary time or sedentary patterns.
In a study just published in PLOS ONE -with Prof. Mai Chin A Paw as first author- we aimed to establish evidence-based accelerometer data reduction criteria to accurately assess total sedentary time and sedentary patterns in children. More than 1000 children in five countries in Europe wore accelerometersfor at least 6 consecutive days. We explored 1) non-wear time criteria; 2) minimum daily valid wear time; 3) differences between weekday and weekend day; and 4) minimum number of days of accelerometer wear by comparing the effects of commonly used data reduction decisions on total sedentary time, and duration and number of prolonged sedentary bouts.
More than 60 consecutive minutes of zero counts was the optimal criterion for non-wear time. Increasing the definition of a valid day from 8 to 10 hours wear time hardly influenced the sedentary outcomes, while the sample size of children with more than 4 valid days increased from 69 to 81%. On weekdays, children had on average 1 hour more wear time, 50 minutes more total sedentary time, 26 minutes more sedentary time accumulated in bouts, and 1 more sedentary bout. At least 6 days of accelerometer data were needed to accurately represent weekly sedentary time and patterns.