The longitudinal influence of home and neighbourhood environments on children's body mass index and physical activity over 5 years : the CLAN study

Objective: To determine the independent contributions of family and neighbourhood environments to changes in youth physical activity and body mass index (BMI) z-score over 5 years.

Methods: In 2001, 2004 and 2006, 301 children (10–12 years at baseline) had their height and weight measured (BMI was converted to z-scores using Centers for Disease Control and Prevention reference charts; see http://www.cdc.gov/growthcharts) and moderate-to-vigorous physical activity (MVPA) assessed using accelerometers. In 2001, parents reported on the home environment (social support, role modelling, rules and restrictions, physical environment) and perceived neighbourhood environment (local traffic, road safety, sporting venues, public transport), and Geographic Information Systems were used to map features of the neighbourhood environment (destinations, road connectivity, traffic exposure). Generalized estimating equations were used to predict average BMI z-score and MVPA over time from baseline home and perceived and objective neighbourhood environment factors.

Results: Among boys, maternal education and heavy traffic were inversely associated, and sibling physical activity, maternal role modelling of MVPA and the presence of dead-end roads were positively associated with MVPA. Having unmarried parents, maternal MVPA role modelling and number of home sedentary items were positively associated with BMI z-score among boys. Among girls, having siblings, paternal MVPA role modelling, physical activity rules and parental physical activity co-participation were positively associated with MVPA. Having unmarried parents and maternal sedentary behaviour role modelling were positively associated, and number of sedentary behaviour rules and physical activity items were inversely associated with BMI z-score among girls.

Conclusion: The home environment seems more important than the neighbourhood environment in influencing children's physical activity and BMI z-score over 5 years. Physical activity and weight gain programmes among youth should focus on parental role modelling, rules around sedentary and active pursuits, and parental support for physical activity. Intervention studies to investigate these strategies are warranted.

An index of unhealthy lifestyle is associated with coronary heart disease mortality rates for small areas in England after adjustment for deprivation

Indices of socio-economic deprivation are often used as a proxy for differences in the health behaviours of populations within small areas, but these indices are a measure of the economic environment rather than the health environment. Sets of synthetic estimates of the ward-level prevalence of low fruit and vegetable consumption, obesity, raised blood pressure, raised cholesterol and smoking were combined to develop an index of unhealthy lifestyle. Multi-level regression models showed that this index described about 50% of the large-scale geographic variation in CHD mortality rates in England, and substantially adds to the ability of an index of deprivation to explain geographic variations in CHD mortality rates.

Estimating process capability index Cpm using a bootstrap sequential sampling procedure

Construction of a confidence interval for process capability index CPM is often based on a normal approximation with fixed sample size. In this article, we describe a different approach in constructing a fixed-width confidence interval for process capability index CPM with a preassigned accuracy by using a combination of bootstrap and sequential sampling schemes. The optimal sample size required to achieve a preassigned confidence level is obtained using both two-stage and modified two-stage sequential procedures. The procedure developed is also validated using an extensive simulation study.

Pre-exercise carbohydrate ingestion : effect of the glycemic index on endurance exercise performance

Purpose: This study aimed to examine the effect of glycemic index of pre-exercise carbohydrate (CHO) ingestion on exercise metabolism and performance.

Methods: Eight endurance trained men ingested a high glycemic index (HGI), low glycemic index (LGI), or a placebo (CON) meal 45 min before exercise and then cycled for 50 min at 67% V·O_2max. Subjects subsequently performed a 15-min self-paced performance ride in which total work (kJ) was recorded.

Results: Plasma glucose concentrations were higher (P < 0.01) after ingestion in HGI compared with LGI and CON (7.53 ± 0.64 vs 5.55 ± 0.21 and 4.65 ± 0.14 mmol·L^-1 for HGI, LGI, and CON, respectively, 30 min postprandial; mean ± SE) but declined at the onset of exercise and were lower (P < 0.01) compared with LGI and CON (4.03 ± 0.31 vs 4.64 ± 0.24 and 5.09 ± 0.16 mmol·L^-1 for HGI, LGI, and CON respectively; mean ± SE) at 10 min of exercise. Plasma glucose remained depressed (P < 0.01) until 30 min into exercise in HGI compared with other trials. Plasma insulin concentrations were higher (P < 0.01) following ingestion during rest and exercise in HGI compared with LGI and CON. Plasma FFA concentrations were lower (P < 0.05) following ingestion in HGI and LGI compared with CON and higher (P < 0.05) in LGI compared with HGI at the start and end of exercise. RER and CHO oxidation was higher (P < 0.01) in HGI compared with LGI and CON during submaximal exercise. There were no differences in work output during the performance cycle.


Conclusions: These data indicate that pre-exercise CHO feedings with varying glycemic indexes do not affect exercise performance following short term submaximal exercise despite alterations in metabolism.