Nicola L. Hawley

Long-term trends in food availability, food prices, and obesity in Samoa

Objectives: To describe long‐term food availability and prices from 1961 to 2007 and body mass index (BMI) trends from 1980 to 2010 in Samoa, and to contextualize these trends within political, economic, cultural, behavioral, and climatic influences.

Ethnic and sex differences in skeletal maturation among the Birth to Twenty cohort in South Africa

Aim To examine ethnic and sex differences in the pattern of skeletal maturity from adolescence to adulthood using a novel longitudinal analysis technique (SuperImposition by Translation And Rotation (SITAR)). Setting Johannesburg, South Africa. Participants 607 boys and girls of black as well as white ethnicity from the Birth to Twenty bone health study, assessed annually from 9 to 20 years of age. Outcome measure Bone maturity scores (Tanner–Whitehouse III radius, ulna, and short bones (TW3 RUS)) assessed longitudinally from hand-wrist radiographs were used to produce individual and mean growth curves of bone maturity and analysed by the SITAR method. Results The longitudinal analysis showed that black boys matured later by 7.0 SE 1.6 months (p<0.0001) but at the same rate as white boys, whereas black girls matured at the same age but at a faster rate than white girls (by 8.7% SE 2.6%, p=0.0007). The mean curves for bone maturity score consistently showed a midpubertal double kink, contrasting with the quadratic shape of the commonly used reference centile curves for bone maturity (TW3). Conclusions Skeletal maturity was reached 1.9 years earlier in girls than boys, and the pattern of maturation differed between the sexes. Within girls, there were no ethnic differences in the pattern or timing of skeletal maturity. Within boys, however, skeletal maturity was delayed by 7 months in black compared with white ethnicity. Skeletal maturation, therefore, varies differentially by sex and ethnicity. The delayed maturity of black boys, but not black girls, supports the hypothesis that boys have greater sensitivity to environmental constraints than girls.

Obesity and Diabetes in Pacific Islanders: the Current Burden and the Need for Urgent Action

Non-communicable diseases (NCDs) now account for more than 36 million deaths each year; many of which are premature. Pacific Islanders are some of the worst afflicted by obesity and diabetes with prevalence of both diseases rising disproportionately faster in the Pacific region over the past three decades than in the rest of the world. A high burden of disease is also found among enclaves of Pacifican migrants in the USA, Australia, and New Zealand. Urgent action is needed to alleviate the high economic and personal costs now associated with NCDs in Pacific Islanders. In this article, we describe contributors to the temporal trends in obesity and diabetes, discuss the current burden of disease in the Pacific Islands and among migrant communities, and suggest priorities for future research in this area. Finally, we discuss challenges unique to intervention among Pacific Islanders and highlight promising opportunities to reduce the NCD burden.

Epigenetic patterns in successful weight loss maintainers: a pilot study

DNA methylation changes occur in animal models of calorie restriction, simulating human dieting, and in human subjects undergoing behavioral weight loss interventions. This suggests that obese (OB) individuals may possess unique epigenetic patterns that may vary with weight loss. Here, we examine whether methylation patterns in leukocytes differ in individuals who lost sufficient weight to go from OB to normal weight (NW; successful weight loss maintainers; SWLMs) vs currently OB or NW individuals. This study examined peripheral blood mononuclear cell (PBMC) methylation patterns in NW (n=16, current/lifetime BMI 18.5–24.9) and OB individuals (n=16, current body mass index (BMI)⩾30), and SWLM (n=16, current BMI 18.5–24.9, lifetime maximum BMI ⩾30, average weight loss 57.4 lbs) using an Illumina Infinium HumanMethylation450 BeadArray. No leukocyte population-adjusted epigenome-wide analyses were significant; however, potentially differentially methylated loci across the groups were observed in ryanodine receptor-1 (RYR1; P=1.54E−6), myelin protein zero-like 3 (MPZL3; P=4.70E−6) and alpha 3c tubulin (TUBA3C; P=4.78E−6). In 32 obesity-related candidate genes, differential methylation patterns were found in brain-derived neurotrophic factor (BDNF; gene-wide P=0.00018). In RYR1, TUBA3C and BDNF, SWLM differed from OB but not NW. In this preliminary investigation, leukocyte SWLM DNA methylation patterns more closely resembled NW than OB individuals in three gene regions. These results suggest that PBMC methylation is associated with weight status.

Prevalence of adiposity and associated cardiometabolic risk factors in the Samoan genome-wide association study.

To describe the prevalence of obesity‐related noncommunicable diseases (NCDs) and associated risk factors in a sample of Samoan adults studied in 2010 as part of a genome‐wide assocation study (GWAS) for obesity related traits.

Stratified randomization controls better for batch effects in 450K methylation analysis: a cautionary tale

Background: Batch effects in DNA methylation microarray experiments can lead to spurious results if not properly handled during the plating of samples. Methods: Two pilot studies examining the association of DNA methylation patterns across the genome with obesity in Samoan men were investigated for chip- and row-specific batch effects. For each study, the DNA of 46 obese men and 46 lean men were assayed using Illuminas Infinium HumanMethylation450 BeadChip. In the first study (Sample One), samples from obese and lean subjects were examined on separate chips. In the second study (Sample Two), the samples were balanced on the chips by lean/obese status, age group, and census region. We used methylumi, watermelon, and limma R packages, as well as ComBat, to analyze the data. Principal component analysis and linear regression were, respectively, employed to identify the top principal components and to test for their association with the batches and lean/obese status. To identify differentially methylated positions (DMPs) between obese and lean males at each locus, we used a moderated t-test. Results: Chip effects were effectively removed from Sample Two but not Sample One. In addition, dramatic differences were observed between the two sets of DMP results. After “removing” batch effects with ComBat, Sample One had 94,191 probes differentially methylated at a q-value threshold of 0.05 while Sample Two had zero differentially methylated probes. The disparate results from Sample One and Sample Two likely arise due to the confounding of lean/obese status with chip and row batch effects. Conclusion: Even the best possible statistical adjustments for batch effects may not completely remove them. Proper study design is vital for guarding against spurious findings due to such effects.

The contribution of feeding mode to obesogenic growth trajectories in American Samoan infants

What is already known about this subject Samoan adults are recognized for their particularly high body mass index and prevalent obesity. While Polynesians are understudied, in other populations infancy is a critical period in the development of obesity. Breastfeeding has been shown to attenuate obesity risk.

Effect of experimental change in children's sleep duration on television viewing and physical activity

Paediatric observational studies demonstrate associations between sleep, television viewing and potential changes in daytime activity levels.

Development of a Behavioral Sleep Intervention as a Novel Approach for Pediatric Obesity in School-aged Children

Despite being the focus of widespread public health efforts, childhood obesity remains an epidemic worldwide. Given the now well-documented consequences of obesity for childhood health and psychosocial functioning, as well as associated morbidity in adulthood, identifying novel, modifiable behaviors that can be targeted to improve weight control is imperative. Enhancing childrens sleep may show promise in assisting with weight regulation. The present paper describes the development of a brief behavioral sleep intervention for school-aged children, including preliminary findings of this work as well as areas for future study.

Determinants of relative skeletal maturity in South African children

The variation of skeletal maturity about chronological age is a sensitive indicator of population health. Age appropriate or advanced skeletal maturity is a reflection of adequate environmental and social conditions, whereas delayed maturation suggests inadequate conditions for optimal development. There remains a paucity of data, however, to indicate which specific biological and environmental factors are associated with advancement or delay in skeletal maturity. The present study utilises longitudinal data from the South African Birth to Twenty (Bt20) study to indentify predictors of relative skeletal maturity (RSM) in early adolescence. A total of 244 black South African children (n=131 male) were included in this analysis. Skeletal maturity at age 9/10 years was assessed using the Tanner and Whitehouse III RUS technique. Longitudinal data on growth, socio-economic position and pubertal development were entered into sex-specific multivariable general linear regression models with relative skeletal maturity (skeletal age-chronological age) as the outcome. At 9/10 years of age males showed an average of 0.66 years delay in skeletal maturation relative to chronological age. Females showed an average of 1.00 year delay relative to chronological age. In males, being taller at 2 years (p<0.01) and heavier at 2 years (p<0.01) predicted less delay in RSM at age 9/10 years, independent of current size and body composition. In females, both height at 2 years and conditional weight at 2 years predicted less delay in RSM at 9/10 years (p<0.05) but this effect was mediated by current body composition. Having greater lean mass at 9/10 years was associated with less delayed RSM in females (p<0.01) as was pubertal status at the time of skeletal maturity assessment (p<0.01). This study identifies several predictors of skeletal maturation at 9/10 years, indicating a role for early life exposures in determining the rate of skeletal maturation during childhood independently of current stature.