Using compositional data analysis to explore accumulation of sedentary behavior,physical activity and youth health

Purpose:The study aimed to describe youth time-use compositions,focusing on time spent in shorter and longer bouts of sedentary behavior and physical activity(PA),and to examine associations of these time-use compositions with cardiometabolic biomarkers.Methods:Accelerometer and cardiometabolic biomarker data from 2 Australian studies involving youths 7-13 years old were pooled(complete cases with accelerometry and adiposity marker data,n=782).A 9-component time-use composition was formed using compositional data analysis:time in shorter and longer bouts of sedentary behavior;time in shorter and longer bouts of light-,moderate-,or vigorous-intensity PA;and"other time"(i.e.,non-wear/sleep).Shorter and longer bouts of sedentary time were defined as<5 min and>5 min,respectively.Shorter bouts of light-,moderate-,and vigorous-intensity PA were defined as<1 min;longer bouts were defined as≥1 min.Regression models examined associations between overall time-use composition and cardiometabolic biomarkers.Then,associations were derived between ratios of longer activity patterns relative to shorter activity patterns,and of each intensity level relative to the other intensity levels and"other time",and cardiometabolic biomarkers.Results:Confounder-adjusted models showed that the overall time-use composition was associated with adiposity,blood pressure,lipids,and the summary score.Specifically,more time in longer bouts of light-intensity PA relative to shorter bouts of light-intensity PA was significantly associated with greater body mass index z-score(zBMI)(β=1.79;SE=0.68)and waist circumference(β=18.35,SE=4.78).When each activity intensity was considered relative to all higher intensities and"other time",more time in light-and vigorous-intensity PA,and less time in sedentary behavior and moderate-intensity PA,were associated with lower waist circumference.Conclusion:Accumulating PA,particularly light-intensity PA,in frequent short bursts may be more beneficial for limiting adiposity compared to accumulating the same amount of PA at these intensities in longer bouts.     

Persistence in the determination of work-related training participation: Evidence from the BHPS, 1991–1997

In this paper we investigate the role of workers’ training history in determining current training-incidence. The analysis is conducted on an unbalanced sample comprising information on approximately 5000 employees from the first seven waves of the BHPS. Training participation is modelled as a dynamic random effects probit model where the effects of unobserved heterogeneity and initial conditions are accounted for in a fashion consistent with methods proposed by Chamberlain (1984) and Wooldridge (2005), respectively. The results suggest that prior training experience is a significant determinant of a worker's participation in a current training episode comparable with other formal educational qualifications.     

Policy Options for Early Childhood: A Model for Decision Making

There is a substantial and documented need for policies to provide comprehensive health, social work, and early education services for young children and their families. Public subsidies to support other enterprises deemed in the public interest are public transportation, higher education, and social security. Childcare would seem to be another such responsibility. The majority of parents with children under the age of five are in the work force, there is documentation of the importance of early experience to brain growth, and further evidence that current child care provisions are often mediocre to poor. This article presents a decision making matrix, which displays major policy options for early childhood and a range of criteria by which to judge the relative efficacy of those options. Several special issues connected with the decision making are discussed.     

Government R&D subsidies as a signal for private investors

Government subsidies for R&D are intended to promote projects with high returns to society but too little private returns to be beneficial for private investors. This may be caused by spillovers or a low appropriability rate. Apart from the direct funding of these projects, government grants may serve as a signal for good investments for private investors. We use a simple signaling model with different types of R&D projects to capture this phenomenon. The agency has a preference for basic research projects as they promise high expected social returns, while banks prefer applied research projects with high private returns. In a setup where the subsidy can only be used to distinguish between basic and applied research projects, government agency’s signal is not very helpful for banks. However, if the subsidy is accompanied by a quality signal, it can lead to increased or better selected private investments.     

Popcorn mystery

Robin Bauer lives in Blaine, Minnesota with her husband, two daughters, three cats, and a dog. She is a member of The Society Of Children's Book Writers.