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1.  The Origins and Genetic Distinctiveness of the Chamorros of the Marianas Islands: An mtDNA Perspective 
Background
Archaeological and linguistic evidence suggests the Marianas Islands were settled around 3,600 years before present (ybp) from Island Southeast Asia (ISEA). Around 1,000 ybp latte stone pillars and the first evidence of rice cultivation appear in the Marianas. Both traditions are absent in the rest of prehistoric Oceania.
Objective
To examine the genetic origins and postsettlement gene flow of Chamorros of the Marianas Islands.
Methods
To infer the origins of the Chamorros we analyzed ~360 base pairs of the hypervariable-region 1 (HVS1) of mitochondrial DNA from 105 Chamorros from Guam, Rota, and Saipan, and the complete mitochondrial genome of 32 Guamanian Chamorros, and compared them to lineages from ISEA and neighboring Pacific archipelagoes from the database.
Results
Results reveal that 92% of Chamorros belong to haplogroup E, also found in ISEA but rare in Oceania. The two most numerous E lineages were identical to lineages currently found in Indonesia, while the remaining E lineages differed by only one or two mutations and all were unique to the Marianas. Seven percent of the lineages belonged to a single Chamorro-specific lineage within haplogroup B4, common to ISEA as well as Micronesia and Polynesia.
Conclusions
These patterns suggest a small founding population had reached and settled the Marianas from ISEA by 4,000 ybp, and developed unique mutations in isolation. A second migration from ISEA may have arrived around 1,000 ybp, introducing the latte pillars, rice agriculture and the homogeneous minority B4 lineage.
doi:10.1002/ajhb.22349
PMCID: PMC4335639  PMID: 23180676
2.  Quantifying Calcium Intake in School Age Children: Development and Validation of the Calcium Counts!© Food Frequency Questionnaire 
Quantifying dietary behavior is difficult and can be intrusive. Calcium, an essential mineral for skeletal development during childhood, is difficult to assess. Few studies have examined the use of food frequency questionnaires (FFQs) for assessing calcium intake in school-age children. This study evaluated the validity and reliability of the Calcium Counts!© FFQ (CCFFQ) for estimating calcium intake in school children in the US. Healthy children, aged 7–10 years (n = 139) completed the CCFFQ and 7-day weighed food records. A subset of subjects completed a second CCFFQ within 3.6 months. Concurrent validity was determined using Pearson correlations between the CCFFQ and food record estimates of calcium intake, and the relationship between quintiles for the two measures. Predictive validity was determined using generalized linear regression models to explore the effects of age, race, and gender. Inter- and intra-individual variability in calcium intake was high (>300 mg/day). Calcium intake was ~300 mg/day higher by CCFFQ compared to food records. Concurrent validity was moderate (r = 0.61) for the entire cohort and higher for selected subgroups. Predictive validity estimates yielded significant relationships between CCFFQ and food record estimates of calcium intake alone and in the presence of such potential effect modifiers as age group, race, and gender. Test–retest reliability was high (r = 0.74). Although calcium intake estimated by the CCFFQ was greater than that measured by food records, the CCFFQ provides valid and reliable estimates of calcium intake in children. The CCFFQ is especially well-suited as a tool to identify children with low calcium intakes.
doi:10.1002/ajhb.20975
PMCID: PMC4334123  PMID: 19621431
3.  The Effects of Market Integration on Childhood Growth and Nutritional Status: the Dual Burden of Under- and Over-Nutrition in the Northern Ecuadorian Amazon 
Objectives
Market integration is an important source of cultural change exposing indigenous populations to epidemiologic and nutrition transitions. As children and adolescents are biologically sensitive to the health effects of market integration, we examine community variation of anthropometric indicators of nutritional status and growth among a cross-cultural sample of Kichwa, Shuar, Huaorani and Cofán indigenous groups in the northern Ecuadorian Amazon.
Methods
We measured height, weight, body mass index (BMI), upper arm circumference and triceps skinfolds of 186 children and adolescents aged two to 18 years from seven communities. Anthropometric z-scores were calculated based on the National Health and Nutritional Examination Survey. Comparisons were made to this US reference group, along with between community differences to contextually explore the impacts of varying degrees of market integration.
Results
We found a high prevalence of stunting in both boys (40%) and girls (34%). Adiposity increased with age and 40% of girls between 15 and 18 years old were overweight. There were large sex differences in body composition with higher BMI, arm circumference and triceps skinfolds in adolescent girls. The Kichwa demonstrated the poorest growth outcomes and nutritional stress followed by the Huaorani and Shuar; yet distinctions in under- and over-nutrition were evident within groups.
Conclusion
Market integration is a major factor influencing the developmental and lifestyle mismatch associated with the epidemiologic and nutrition transition in general, and the dual burden pattern of high rates of stunting yet adequate to above average short-term nutritional status indicators found among indigenous Amazonian populations.
doi:10.1002/ajhb.22404
PMCID: PMC4331102  PMID: 23657874
indigenous health; stunting; overweight; nutrition transition
4.  [No title available] 
PMCID: PMC4292846  PMID: 24799123
5.  Pathogenic and Obesogenic Factors Associated with Inflammation in Chinese Children, Adolescents and Adults 
Objectives
Influenced by pathogen exposure and obesity, inflammation provides a critical biological pathway linking changing environments to the development of cardiometabolic disease. This study tests the relative contribution of obesogenic and pathogenic factors to moderate and acute CRP elevations in Chinese children, adolescents and adults.
Methods
Data come from 8795 participants in the China Health and Nutrition Study. Age-stratified multinomial logistic models were used to test the association between illness history, pathogenic exposures, adiposity, health behaviors and moderate (1-10 mg/L in children and 3-10 mg/L in adults) and acute (>10mg/L) CRP elevations, controlling for age, sex and clustering by household. Backward model selection was used to assess which pathogenic and obesogenic predictors remained independently associated with moderate and acute CRP levels when accounting for simultaneous exposures.
Results
Overweight was the only significant independent risk factor for moderate inflammation in children (RRR 2.10, 95%CI 1.13-3.89). History of infectious (RRR 1.28, 95%CI 1.08-1.52) and non-communicable (RRR 1.37, 95%CI 1.12-1.69) disease, overweight (RRR 1.66, 95%CI 1.45-1.89) and high waist circumference (RRR 1.63, 95%CI 1.42-1.87) were independently associated with a greater likelihood of moderate inflammation in adults while history of infectious disease (RRR 1.87, 95%CI 1.35-2.56) and overweight (RRR 1.40, 95%CI 1.04-1.88) were independently associated with acute inflammation. Environmental pathogenicity was associated with a reduced likelihood of moderate inflammation, but a greater likelihood of acute inflammation in adults.
Conclusions
These results highlight the importance of both obesogenic and pathogenic factors in shaping inflammation risk in societies undergoing nutritional and epidemiological transitions.
doi:10.1002/ajhb.22462
PMCID: PMC3932143  PMID: 24123588
C-reactive protein; Inflammation; Obesity; Infectious Disease; China; Life course
6.  Prenatal and postnatal energetic conditions and sex steroids levels across the first year of life 
Objectives
Human biologists have documented variability in reproductive maturation, fertility, and cancer risk related to developmental conditions. Yet no previous studies have directly examined the impact of pre- and post-natal energetic environments on sex steroids in infancy, a critical period for hypothalamic-pituitary-gonadal axis development. Thus, we examined the impact of maternal characteristics, birth size, and feeding practices on fecal sex steroid production in a longitudinal sample of 31 American infants followed from 2 weeks to 12 months of age.
Methods
Maternal characteristics and birth size were collected at study enrollment, infant diet was assessed through weekly 24-hr food diaries, and anthropometrics were measured weekly. Fecal estradiol and testosterone levels were assessed weekly using validated microassay RIA techniques. Mixed models were used to test for associations between maternal and birth characteristics, feeding practices, and sex steroids across the first year of life. Formal mediation analysis examined whether the relationship between infant feeding and hormone levels was mediated by infant size.
Results
Maternal and birth characteristics had persistent effects on fecal sex steroid levels, with taller maternal height and larger birth size associated with lower estradiol levels in girls and higher testosterone levels in boys. Infant diet was also associated with sex steroid levels independently of infant size. Formula feeding was associated with higher estradiol levels in boys and girls and with higher testosterone in girls.
Conclusion
These results suggest that markers of early energy availability influence sex hormone levels with potential long-term consequences for reproductive development and function.
doi:10.1002/ajhb.22424
PMCID: PMC4271319  PMID: 23904043
estradiol; testosterone; infancy; infant feeding; birthweight
7.  The anthropometry of children and adolescents may be influenced by the prenatal smoking habits of their grandmothers: A longitudinal cohort study 
American Journal of Human Biology  2014;26(6):731-739.
Objectives
Previously, in the Avon Longitudinal Study of Parents and Children (ALSPAC), we have shown different sex-specific birth anthropometric measurements contingent upon whether or not prenatal smoking was undertaken by paternal grandmother (PGM±), maternal grandmother (MGM±), and the study mother (M±). The findings raised the question as to whether there were long-term associations on the growth of the study children over time.
Methods
Measures of weight, height, body mass index, waist circumference, lean mass, and fat mass of children in the ALSPAC study from 7 to 17 years of age were used. We compared growth in four categories at each age: PGM+M− with PGM−M−; MGM+M− with MGM−M−; PGM+M+ with PGM−M+; MGM+M+ with MGM−M+; and adjusted for housing tenure, maternal education, parity, and paternal smoking at the start of the study pregnancy.
Results
We found that if the PGM had, but the study mother had not, smoked in pregnancy, the girls were taller and both genders had greater bone and lean mass. However, if the MGM had smoked prenatally but the mother had not (MGM+M−), the boys became heavier than expected with increasing age—an association that was particularly due to lean rather than fat mass, reflected in increased strength and fitness. When both the maternal grandmother and the mother had smoked (MGM+M+) girls had reduced height, weight, and fat/lean/bone mass when compared with girls born to smoking mothers whose own mothers had not smoked (MGM−M+).
Conclusions
This study indicates that smoking in humans can have sex-specific transgenerational effects. Am. J. Hum. Biol. 26:731–739, 2014. © 2014 The Authors American Journal of Human Biology Published by Wiley Periodicals, Inc.
doi:10.1002/ajhb.22594
PMCID: PMC4238812  PMID: 25130101
8.  Normalization of elevated cardiac, kidney, and hemolysis plasma markers within 48 h in Mexican Tarahumara runners following a 78 km race at moderate altitude 
American Journal of Human Biology  2014;26(6):836-843.
Objectives
The aim of this study was to examine to what extent extreme endurance exercise results in changes of plasma markers associated with cardiac and renal damage, as well as hemolysis in male, Mexican Tarahumara runners.
Methods
Ten Tarahumara runners (mean (sd) age of 38 (12) years) participated in a 78 km race in Chihuahua, Mexico at 2,400 m above sea level. Cardiac, kidney, and hematology plasma markers were measured pre-race and <5 min, 1 h, 3 h, 6 h, 24 h, and 48 h post-race. Anthropometry, blood pressure, pulse rate, electrocardiography, HbA1c, hemoglobin and VO2max (estimated from heart rate following step test) were assessed pre-race, while physical activity energy expenditure and intensity were estimated during the race, and oxygen partial pressure saturation (SpO2) <30 min post-race.
Results
Estimated mean VO2max was 48 (9) mLO2 min−1 kg−1 and relative intensity during the race was 68 (11)%VO2max. Mean SpO2 was 92 (3)% <30 min post-race. Plasma concentrations of especially total creatine kinase, creatine kinase-MB isoform, and haptoglobin changed significantly from pre-race values (P < 0.001) up to 24 h post-race, but had returned to pre-race values after 48 h. The plasma concentrations of mid-regional proatrial natiuretic peptide and copeptin returned to pre-race concentrations after 1 and 6 h, respectively.
Conclusions
Altered cardiac, renal, and hemolysis plasma markers were normalized after 48 h following 78 km of running, suggesting that the impact of exercise-induced cardiac and kidney damage as well as hemolysis in the Mexican Tarahumara is low. Am. J. Hum. Biol. 26:836–843, 2014. © 2014 The Authors American Journal of Human Biology Published by Wiley Periodicals, Inc.
doi:10.1002/ajhb.22607
PMCID: PMC4237147  PMID: 25145663
9.  Non-Syndromic Brachydactyly Type D and Type E Mapped to 7p15 in Healthy Children and Adults from the Jirel Ethnic Group in Eastern Nepal 
Objectives
There is phenotypic overlap between Brachydactyly Type D (BDD) and Brachydactyly Type E (BDE) that suggests a possible common underlying etiology. We seek to understand the genetic underpinnings of, and relationship between, these skeletal anomalies.
Methods
The Jirel ethnic group of eastern Nepal participates in various genetic epidemiologic studies, including those in which hand-wrist radiographs have been taken to examine skeletal development. 2,130 individuals (969 males; 1,161 females) were phenotyped for BDD/BDE. Of these, 1,722 individuals (773 males; 949 females) were genotyped for 371 STR markers spanning the autosomal genome. Variance components-based linkage analysis was used to conduct a genome-wide linkage scan for QTL influencing the BDD/BDE phenotype.
Results
BDD was present in 3.55%, and BDE was present in 0.39%, of the study sample. Because of the phenotypic overlap between two traits, affecteds of either type were considered as affected by a single combined phenotype (BDD/BDE) having a prevalence of 3.94%. The additive genetic heritability of BDD/BDE was highly significant (h2 ± SE = 0.89 ± 0.13; p = 1.7×10−11). Significant linkage of BDD/BDE was found to markers on chromosome 7p21-7p14 (peak LOD score = 3.74 at 7p15 between markers D7S493 and D7S516).
Conclusions
Possible positional candidate genes in the one-lod support interval of this QTL include TWIST and the HOXA1-A13 cluster. This is the first study to report significant linkage results for BDD/BDE using a large extended pedigree, and the first to suggest that mutations in TWIST and/or the HOXA1-A13 cluster may contribute to these specific skeletal anomalies.
doi:10.1002/ajhb.22441
PMCID: PMC3968259  PMID: 24022874
BDD; BDE; linkage; Chromosome 7
10.  Maternal cortisol disproportionately impacts fetal growth in male offspring: Evidence from the Philippines 
Objectives
Lower birth weight (BW) re-occurs across generations, but the intermediate mechanisms remain poorly understood. One potential pathway involves cortisol, which may be elevated in women born small and in turn could lead to fetal growth restriction in offspring. To test this possibility, we evaluated whether BW predicts hypothalamic-pituitary-adrenal (HPA) function in the non-pregnant state in a cohort of young Filipino women, and whether differences in HPA function predict offspring BW.
Methods
Multiple regression relating maternal BW, adult salivary cortisol profiles and recalled offspring BW (N = 488) among participants of the Cebu Longitudinal Health and Nutrition Survey.
Results
Maternal BW related inversely to evening cortisol in adulthood (p < 0.04). Maternal BW and evening cortisol were both stronger predictors of male than of female BW (maternal BW: p < 0.0001 for males; p = 0.07 for females; bedtime cortisol: p = 0.003 for males; p = 0.3 for females). Waking and thirty minute post-waking cortisol did not predict offspring BW. Controlling for evening cortisol did not diminish the relationship between maternal and offspring BW in males or females.
Conclusions
Being born small predicted higher evening cortisol in adulthood among these young mothers. Lower maternal BW and elevated evening cortisol independently predicted giving birth to lower BW offspring, with effects greatest and only significant among males. We speculate that sex differences in sensitivity to maternal stress hormones could help explain the stronger relationships between BW and CVD risk factors reported among the males in this and other populations.
doi:10.1002/ajhb.21226
PMCID: PMC4181846  PMID: 22121049
cortisol; birth weight; intergenerational effects; sex differences; DOHaD
11.  Wrist Breadth and Homeostasis Model Assessment of Insulin Resistance in Youth: The Fels Longitudinal Study 
Objectives
There is biological crosstalk between insulin signaling and bone remodeling pathways, and wrist circumference and bone area were recently found to associate with insulin resistance independent of body mass index (BMI) in overweight/obese children. We aimed to expand on this work by using more specific measures of adiposity for adjustment and examining children with broader range of BMI.
Methods
We used serial data (1,051 total measures) on 313 non-Hispanic white youth (ages 8–18 y) from the Fels Longitudinal Study with homeostasis model assessment of insulin resistance (HOMA-IR) as the outcome. Internal standard deviation score (SDS) for wrist breadth was evaluated as a predictor of HOMA-IR (log-transformed) before and after adjusting for internal-sample SDSs for BMI, waist circumference (WC), and total body fat (TBF) from dual energy X-ray absorptiometry, in addition to age, sex, Tanner stage, and birth year, using generalized estimating equations.
Results
Before additional adiposity adjustment, we found a significant positive association between wrist breadth SDS and log-transformed HOMA-IR (β = 0.13; 95%CI: 0.09–0.17), which remained significant after adjusting for TBF SDS (β = 0.09; 95%CI: 0.05–0.13; P < 0.001), BMI SDS (β = 0.06; 95%CI: 0.02–0.10; P = 0.007), and WC SDS (β = 0.06; 95%CI: 0.02–0.09; P = 0.005).
Conclusions
Further work is needed to determine whether simple frame size measures such as wrist breadth may be useful markers of metabolic risk.
doi:10.1002/ajhb.22416
PMCID: PMC3988662  PMID: 23897560
12.  Evidence for novel genetic loci associated with metabolic traits in Yup’ik people 
Objectives:
To identify genomic regions associated with fasting plasma lipid profiles, insulin, glucose, and glycosylated hemoglobin in a Yup’ik study population, and to evaluate whether the observed associations between genetic factors and metabolic traits were modified by dietary intake of marine derived omega-3 polyunsaturated acids (n-3 PUFA).
Methods:
A genome-wide linkage scan was conducted among 982 participants of the Center for Alaska Native Health Research study. n-3 PUFA intake was estimated using the nitrogen stable isotope ratio (δ15N) of erythrocytes. All genotyped SNPs located within genomic regions with LOD scores > 2 were subsequently tested for individual SNP associations with metabolic traits using linear models that account for familial correlation as well as age, sex, community group and n-3 PUFA intake. Separate linear models were fit to evaluate interactions between the genotype of interest and n-3 PUFA intake.
Results:
We identified several chromosomal regions linked to serum apolipoprotein A2, high density lipoprotein-, low density lipoprotein-, and total cholesterol, insulin, and glycosylated hemoglobin. Genetic variants found to be associated with total cholesterol mapped to a region containing previously validated lipid loci on chromosome 19, and additional novel peaks of biological interest were identified at 11q12.2-11q13.2. We did not observe any significant interactions between n-3 PUFA intake, genotypes, and metabolic traits.
Conclusions:
We have completed a whole genome linkage scan for metabolic traits in Native Alaskans, confirming previously identified loci, and offering preliminary evidence of novel loci implicated in chronic disease pathogenesis in this population.
doi:10.1002/ajhb.22429
PMCID: PMC3785243  PMID: 23907821
Alaska Native; metabolism; multi-point linkage genome scan
13.  Patterns of Senescence in Human Cardiovascular Fitness: VO2max in Subsistence and Industrialized Populations 
Objectives
This study explores whether cardiovascular fitness levels and senescent decline are similar in the Tsimane of Bolivia and Canadians, as well as other subsistence and industrialized populations. Among Tsimane, we examine whether morbidity predicts lower levels and faster decline of cardiovascular fitness, or whether their lifestyle (e.g., high physical activity) promotes high levels and slow decline. Alternatively, high activity levels and morbidity might counterbalance such that Tsimane fitness levels and decline are similar to those in industrialized populations.
Methods
Maximal oxygen uptake (VO2max) was estimated using a step test heart rate method for 701 participants. We compared these estimates to the Canadian Health Measures Survey and previous studies in industrialized and subsistence populations. We evaluated whether health indicators and proxies for market integration were associated with VO2max levels and rate of decline for the Tsimane.
Results
The Tsimane have significantly higher levels of VO2max and slower rates of decline than Canadians; initial evidence suggests differences in VO2max levels between other subsistence and industrialized populations. Low hemoglobin predicts low VO2max for Tsimane women while helminth infection predicts high VO2max for Tsimane men, though results might be specific to the VO2max scaling parameter used. No variables tested interact with age to moderate decline.
Conclusions
The Tsimane demonstrate higher levels of cardiovascular fitness than industrialized populations, but levels similar to other subsistence populations. The high VO2max of Tsimane is consistent with their high physical activity and few indicators of cardiovascular disease, measured in previous studies.
doi:10.1002/ajhb.22445
PMCID: PMC4142762  PMID: 24022886
14.  Seasonal variation of peripheral blood leukocyte telomere length in Costa Rica: a population based observational study 
Objectives
Peripheral blood leukocyte telomere length is increasingly being used as a biomarker of aging, but its natural variation in human populations is not well understood. Several other biomarkers show seasonal variation, as do several determinants of leukocyte telomere length. We examined whether there was monthly variation in leukocyte telomere length in Costa Rica, a country with strong seasonal differences in precipitation and infection.
Methods
We examined a longitudinal population based cohort of 581 Costa Rican adults age 60 and above, from which blood samples were drawn between October 2006 and July 2008. Leukocyte telomere length was assayed from these samples using the quantitative PCR method. Multivariate regression models were used to examine correlations between month of blood draw and leukocyte telomere length.
Results
Telomere length from peripheral blood leukocytes varied by as much as 200 base pairs depending on month of blood draw, and this difference is not likely to be due to random variation. A moderate proportion of this association is statistically accounted for by month and region specific average rainfall. We found shorter telomere length associated with greater rainfall.
Conclusions
There are two possible explanations of our findings. First, there could be relatively rapid month-to-month changes in leukocyte telomere length. This conclusion would have implications for understanding the natural population dynamics of telomere length. Second, there could be seasonal differences in constituent cell populations. This conclusion would suggest that future studies of leukocyte telomere length use methods to account for the potential impact of constituent cell type.
doi:10.1002/ajhb.22529
PMCID: PMC4136920  PMID: 24615938
telomere length; seasonality; lymphocytes; infection; rainfall
15.  25-Hydroxyvitamin D Levels in African American and Nigerian Women 
Objectives
African Americans have substantially lower levels of circulating 25(OH)D than whites. We compared population-based samples of 25(OH)D in women of African descent from Nigeria and metropolitan Chicago.
Methods
100 Women of Yoruba ethnicity from southwest Nigeria and 94 African American women from metropolitan Chicago were recruited and compared using a standardized survey protocol and the same laboratory assay for 25(OH)D.
Results
Mean 25(OH)D levels were 64 nmol/L among the Nigerians and 29 nmol/L among the African Americans. Only 10% of the values were shared in common between the groups, and 76% of the Nigerians were above the currently defined threshold for adequate circulating 25(OH)D compared to 5% of the African Americans. Modest associations were seen between 25(OH)D and measures of obesity, although adjustment for these traits did not materially affect the group differences.
Conclusion
These data support the presumption that skin color is an adaptive trait which has evolved in part to regulate 25(OH)D. It remains undetermined, however, whether lower values observed in African Americans have negative health consequences.
doi:10.1002/ajhb.22395
PMCID: PMC3980939  PMID: 23559500
vitamin D; African American; Nigerian; obesity
16.  Androgen activity and markers of inflammation among men in NHANES III 
Objectives:
Inflammation contributes to chronic diseases. Lower serum testosterone among men is associated with less inflammation, yet immune defense is thought to trade-off against reproduction with androgens adversely affecting immune function. Anti-androgens are effective at castrate levels of serum testosterone, suggesting serum testosterone may not capture all androgen activity. The association of two androgen biomarkers with key markers of inflammation was examined.
Methods:
The adjusted association of serum testosterone and androstanediol glucuronide with C-reactive protein, white blood cell, granulocyte and lymphocyte count, fibrinogen and hemoglobin, as a control outcome because testosterone administration raises hemoglobin, were examined in a nationally representative sample of 1490 US men from NHANES III phase 1 (1988-91) using multivariable linear regression.
Results:
Serum testosterone and androstanediol glucuronide were weakly correlated (0.13). Serum testosterone was associated with lower white blood cell count (−0.26*10−9 per standard deviation, 95% confidence interval (CI) −0.37 to −0.14) and granulocyte count (−0.21*10−9, 95% CI −0.29 to −0.13) but not with hemoglobin (0.02 g/L, 95% CI −0.89 to 0.92), adjusted for age, education, race/ethnicity, smoking and alcohol. Similarly adjusted, androstanediol glucuronide was not associated with white blood cell count (0.10*10−9, 95% CI −0.05 to −0.25), granulocyte count (0.12*10−9, 95% CI −0.02 to 0.25) or fibrinogen (0.05g/L, 95% CI −0.004 to 0.11), but was with hemoglobin (0.70g/L, 95% CI 0.07 to 1.32).
Conclusions:
Different androgen biomarkers had different associations with inflammatory markers, highlighting the need to consider several androgen biomarkers. The possibility remains that androgens may generate inflammatory processes with implications for chronic diseases.
doi:10.1002/ajhb.22421
PMCID: PMC4030427  PMID: 23943465
testosterone; androgen glucuronide; C-reactive protein; fibrinogen; leukocyte
17.  Characterization of the Infant BMI Peak: Sex Differences, Birth Year Cohort Effects, Association with Concurrent Adiposity, and Heritability 
Objectives
To characterize an early trait in the BMI-for-age curve, the infant BMI peak.
Methods
BMI-for-age curves were produced for 747 non-Hispanic, white Fels Longitudinal Study participants, from which individual age (AgePeak) and BMI (BMIPeak) at maximum infant BMI were estimated. Multivariable general linear regression was used to examine the effects of sex and birth year cohort (1929–1950, 1951–1970, and 1971–2010) on AgePeak and BMIPeak, with associations between BMIPeak and concurrent sum of four skinfold thicknesses assessed in a subsample (N = 155). Heritability (h2) of AgePeak and BMIPeak was estimated using maximum-likelihood variance components analysis.
Results
AgePeak occurred at 9 months of age in both sexes, but BMIPeak was 0.4 kg/m2 higher for boys than for girls (P-value < 0.001). Infants born between 1971 and 2010 experienced a 1.5 month earlier AgePeak and a 0.35 kg/m2 lower BMIPeak than infants born between 1929 and 1950 (P-values < 0.001). Skinfold thickness explained 37% of the variance in BMIPeak in boys and 20% of the variance in girls (p-values < 0.001). AgePeak and BMIPeak were significantly heritable (h2 = 0.54 and 0.75, respectively).
Conclusions
Both AgePeak and BMIPeak decreased over successive birth year cohorts in the Fels Longitudinal Study. Despite a positive association of BMIPeak with concurrent adiposity, AgePeak appears to occur later than does the well-documented peak in infant fat mass and BMIPeak does not capture known sex differences in infant adiposity. Strong heritability of these infant BMI traits suggests investigation of genetic control, and validation of their relationship to body composition is greatly needed.
doi:10.1002/ajhb.22385
PMCID: PMC3988701  PMID: 23606227
18.  Bayesian Longitudinal Plateau Model of Adult Grip Strength 
Objectives
This article illustrates the use of applied Bayesian statistical methods in modeling the trajectory of adult grip strength and in evaluating potential risk factors that may influence that trajectory.
Methods
The data consist of from 1 to 11 repeated grip strength measurements from each of 498 men and 533 women age 18–96 years in the Fels Longitudinal Study (Roche AF. 1992. Growth, maturation and body composition: the Fels longitudinal study 1929–1991. Cambridge: Cambridge University Press). In this analysis, the Bayesian framework was particularly useful for fitting a nonlinear mixed effects plateau model with two unknown change points and for the joint modeling of a time-varying covariate. Multiple imputation (MI) was used to handle missing values with posterior inferences appropriately adjusted to account for between-imputation variability.
Results
On average, men and women attain peak grip strength at the same age (36 years), women begin to decline in grip strength sooner (age 50 years for women and 56 years for men), and men lose grip strength at a faster rate relative to their peak; there is an increasing secular trend in peak grip strength that is not attributable to concurrent secular trends in body size, and the grip strength trajectory varies with birth weight (men only), smoking (men only), alcohol consumption (men and women), and sports activity (women only).
Conclusions
Longitudinal data analysis requires handling not only serial correlation but often also time-varying covariates, missing data, and unknown change points. Bayesian methods, combined with MI, are useful in handling these issues.
doi:10.1002/ajhb.21057
PMCID: PMC3988672  PMID: 20737612
19.  Women’s Autonomy and its Relationship to Children’s Nutrition Among the Rendille of Northern Kenya 
This study explores the effect of women’s autonomy on children’s health. Research was conducted among the Rendille, a traditionally nomadic pastoralist population living in northern Kenya. Using data collected from 435 women and 934 of their children, we tested the hypothesis that women with higher levels of autonomy would have children with better nutrition. Results of our study indicated that while women’s autonomy had no effect on younger—ages 0–35 months—children’s nutrition as measured by WHZ scores, greater levels of women’s autonomy were significantly associated with improved nutrition among older—ages 3–10 years—children. These results suggest that women’s autonomy is an important factor in relation to children’s health in some circumstances. In addition to exploring the applied aspects of our findings, we also suggest how considering the concept of women’s autonomy may add to the existing literature on parental investment.
doi:10.1002/ajhb.20815
PMCID: PMC3962675  PMID: 18792063
20.  Age at First Reproduction and Economic Change in the Context of Differing Kinship Ecologies 
Kinship systems which tend to be based on ecologies of subsistence also assign differential power, privilege and control to human connections that present pathways for manipulation of resource access and transfer. They can be used in this way to channel resource concentrations in women and hence their reproductive value. Thus, strategic female life course trade-offs and their timing are likely to be responsive to changing preferences for qualities in women as economic conditions change. Female life histories are studied in two ethnic groups with differing kinship systems in N.E. India where the competitive market economy is now being felt by most households. Patrilineal Bengali (599 women) practice patrilocal residence with village exogamy and matrilineal Khasi (656 women) follow matrilocal residence with village endogamy, both also normatively preferring three-generation extended households. These households have helpful senior women and significantly greater income. Age at first reproduction (AFR), achieved adult growth (height) and educational level (greater than 6 yrs or less) are examined in reproductive women, ages 16–50. In both groups, women residing normatively are older at AFR and taller than women residing non-normatively. More education is also associated with senior women. Thus, normative residence may place a woman in the best reproductive location, and those with higher reproductive and productive potential are often chosen as households face competitive market conditions. In both groups residing in favorable reproductive locations is associated with a faster pace of fertility among women, as well as lower offspring mortality among Khasi, to compensate for a later start.
doi:10.1002/ajhb.20929
PMCID: PMC3951325  PMID: 19384863
21.  Maturity-Associated Variation in Total and Depot-Specific Body Fat in Children and Adolescents 
Objectives
This study considered the association between sexual maturation and adiposity in children and adolescents, and examined the contribution of sexual maturation to ethnic differences in total and depot-specific body fat.
Methods
The sample included 382 White and African American 5–18-year-olds. Body mass index (BMI), waist circumference (WC) and sexual maturity status (breast/genital and pubic hair stage) were assessed in a clinical setting. Total body fat (TBF) was measured by dual-energy X-ray absorptiometry and abdominal subcutaneous (SAT) and visceral adipose tissue (VAT) were measured by magnetic resonance imaging. Analysis of covariance adjusted for age was used to examine the association between sexual maturity status and adiposity, and linear regression adjusted for age was used to examine the influence of sexual maturation on ethnic differences in adiposity. Analysis of VAT also controlled for TBF. Significance was accepted at P<0.05.
Results
Breast/genital stage was significantly associated with BMI, WC, TBF, and SAT in girls of both ethnic groups and in White boys. Breast stage was associated with VAT. Stage of pubic hair was significantly associated with TBF and VAT in White girls only. In girls, sexual maturation attenuated the ethnic effects on BMI and WC, but the ethnic effect in VAT persisted. In boys, sexual maturation did not attenuate ethnic differences on VAT and did not predict WC or SAT. Sexual maturity status independently explained variance in adiposity in girls only.
Conclusions
Sexual maturity status is an important determinant of pediatric adiposity and attenuates ethnic differences in girls’ adiposity.
doi:10.1002/ajhb.22380
PMCID: PMC3947527  PMID: 23564417
22.  Vitamin A Dynamics in Breastmilk and Liver Stores: A Life History Perspective 
Objectives
Newborns are dependent on breastmilk vitamin A for building hepatic stores of vitamin A that will become critical for survival after weaning. It has been documented that vitamin A concentrations in breastmilk decline across the first year postpartum in both well-nourished and malnourished populations. The reason for this decline has been assumed to be a sign of concurrently depleting maternal hepatic stores. This study investigates this assumption to clarify why the decline occurs, drawing on life history theory.
Methods
A cross sectional survey was conducted among lactating mothers in Kenya in 2006. Data were used to examine (1) the relationship between liver vitamin A and time, (2) if the relationship between milk and liver vitamin A varies by time, and (3) by maternal parity.
Results
The relationship between liver vitamin A and time fits the quadratic pattern with marginal significance (P = 0.071, n = 192); the liver vitamin A declined during early postpartum then recovered in late postpartum time, controlling covariates. The milk-liver vitamin A relationship varied by postpartum time periods (P = 0.03) and by maternal parity (P = 0.005). Mothers in earlier postpartum or higher parity had a stronger positive relationship between milk and liver vitamin A than mothers in later postpartum or lower parity.
Conclusions
Our observations are consistent with life history tradeoffs and negate the assumption that maternal hepatic and milk vitamin A decline together. Rather, maternal liver vitamin A has a dynamic relationship with milk vitamin A, particularly depending on postpartum time and maternal parity.
doi:10.1002/ajhb.21195
PMCID: PMC3938187  PMID: 21695742
23.  Evaluation of Iron Deficiency As a Nutritional Adaptation to Infectious Disease: An Evolutionary Medicine Perspective 
An evolutionary perspective suggests that iron deficiency may have opposing effects on infectious disease risk, decreasing susceptibility by restricting iron availability to pathogens, and increasing susceptibility by compromising cellular immunocompetence. In some environments, the trade-off between these effects may result in optimal iron intake that is inadequate to fully meet body iron needs. Thus, it has been suggested that moderate iron deficiency may protect against acute infection, and may represent a nutritional adaptation to endemic infectious disease stress. To test this assertion, we examined the association between infection, reflected by C-reactive protein, a biomarker of inflammation, and iron status, reflected by transferrin receptor (TfR) and zinc protoporphyrin to heme ratio (ZPP:H), among school-age Kenyan children, and evaluated the hypothesis that moderate iron deficiency is associated with lower odds of infectious disease. TfR > 5.0 mg/l, with sensitivity and specificity for iron deficiency (ZPP:H > 80 μmol/mol) of 0.807 and 0.815, was selected as the TfR definition of iron deficiency. Controlling for age and triceps skinfold thickness (TSF), the odds ratio (OR) for acute viral or bacterial infection associated with iron deficiency (compared to normal/replete) was 0.50 (P = 0.11). Controlling for age and TSF, the OR for infection associated with an unequivocally iron replete state (compared to all others) was 2.9 (P = 0.01). We conclude that iron deficiency may protect against acute infection in children.
doi:10.1002/ajhb.20839
PMCID: PMC3938201  PMID: 18949769
24.  Measured Maximal Heart Rates Compared to Commonly Used Age-Based Prediction Equations in the Heritage Family Study 
Objective
The purpose of this study was to examine how well two commonly used age-based prediction equations for maximal heart rate (HRmax) estimate the actual HRmax measured in Black and White adults from the HERITAGE Family Study.
Methods
A total of 762 sedentary subjects (39% Black, 57% Females) from HERITAGE were included. HRmax was measured during maximal exercise tests using cycle ergometers. Age-based HRmax was predicted using the Fox (220-age) and Tanaka (208 – 0.7 × age) formulas.
Results
The standard error of estimate (SEE) of predicted HRmax was 12.4 and 11.4 bpm for the Fox and Tanaka formulas, respectively, indicating a wide-spread of measured-HRmax values are compared to their age-predicted values. The SEE (shown as Fox/Tanaka) was higher in Blacks (14.4/13.1 bpm) and Males (12.6/11.7 bpm) compared to Whites (11.0/10.2 bpm) and Females (12.3/11.2 bpm) for both formulas. The SEE was higher in subjects above the BMI median (12.8/11.9 bpm) and below the fitness median (13.4/12.4 bpm) when compared to those below the BMI median (12.2/11.0 bpm) and above the fitness median (11.4/10.3) for both formulas.
Conclusion
Our findings show that based on the SEE, the prevailing age-based estimated HRmax equations do not precisely predict an individual’s measured-HRmax.
doi:10.1002/ajhb.22431
PMCID: PMC3935487  PMID: 23913510
25.  How Boys Grow Determines How Long They Live 
Objectives
Increase in height in modern societies has been accompanied by an in increase in lifespan. The longer lives of taller people suggest that good nutrition during childhood, together with freedom from recurrent minor infection, prolong human life. There is, however, a caveat. Tall adult stature may be the result of rapid “compensatory” growth following a setback. Compensatory growth is known to reduce the lifespan of animals, possibly because it is disorganized.
Methods
We analyzed lifespan among 6,975 men born in Helsinki, Finland, during 1934–44. Their early growth was recorded.
Results
Boys who were tallest at seven years of age had lower all cause mortality, the hazard ratio being 0.79(95%CI 0.70 to 0.89, P < 0.0001) per 10 cm increase in height. There was, however, a group of boys among whom being tall was associated with increased all cause mortality, the hazard ratio being 1.32(1.00 to 1.75, P 5 0.05). These boys were taller at seven years than their birthweight and length at birth predicted. After they were excluded from the analysis, boys who were more than 126 cm in height at seven lived for eight years longer than those who were 114 cm or less. This increase in lifespan was similar to the effect of high socio-economic status in adult life.
Conclusions
Rapid growth in childhood height usually predicts a longer life. But tallness among men may be a misleading indicator of wellbeing and longer life expectancy in populations where compensatory growth is widespread. African Americans may be an example.
doi:10.1002/ajhb.21165
PMCID: PMC3923646  PMID: 21448906

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