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1.  Candidate Gene Association Study of Coronary Artery Calcification in Chronic Kidney Disease: Findings from the Chronic Renal Insufficiency Cohort Study 
To identify loci for coronary artery calcification (CAC) in patients with chronic kidney disease (CKD).
CKD is associated with increased CAC and subsequent coronary heart disease (CHD) but the mechanisms remain poorly defined. Genetic studies of CAC in CKD may provide a useful strategy for identifying novel pathways in CHD.
We performed a candidate gene study (~2,100 genes; ~50,000 SNPs) of CAC within the Chronic Renal Insufficiency Cohort (CRIC) Study (n=1,509; 57% European, 43% African ancestry). SNPs with preliminary evidence of association with CAC in CRIC were examined for association with CAC in PennCAC (n=2,560) and Amish Family Calcification Study (AFCS; n=784) samples. SNPs with suggestive replication were further analyzed for association with myocardial infarction (MI) in the Pakistan Risk of Myocardial Infarction study (PROMIS) (n=14,885).
Of 268 SNPs reaching P <5×10−4 for CAC in CRIC, 28 SNPs in 23 loci had nominal support (P <0.05 and in same direction) for CAC in PennCAC or AFCS. Besides chr9p21 and COL4A1, known loci for CHD, these included SNPs having reported GWAS association with hypertension (e.g., ATP2B1). In PROMIS, four of the 23 suggestive CAC loci (chr9p21, COL4A1, ATP2B1 and ABCA4) had significant associations with MI consistent with their direction of effect on CAC.
We identified several loci associated with CAC in CKD that also relate to MI in a general population sample. CKD imparts a high risk of CHD and may provide a useful setting for discovery of novel CHD genes and pathways.
PMCID: PMC3953823  PMID: 23727086
Coronary artery calcification (CAC); chronic kidney disease (CKD); Chronic Renal Insufficiency Cohort Study (CRIC); myocardial infarction (MI); risk factors; candidate genes; single nucleotide polymorphisms (SNPs)
2.  Genome-Wide Association Study Identifies a Novel Locus Contributing to Type 2 Diabetes Susceptibility in Sikhs of Punjabi Origin From India 
Diabetes  2013;62(5):1746-1755.
We performed a genome-wide association study (GWAS) and a multistage meta-analysis of type 2 diabetes (T2D) in Punjabi Sikhs from India. Our discovery GWAS in 1,616 individuals (842 case subjects) was followed by in silico replication of the top 513 independent single nucleotide polymorphisms (SNPs) (P < 10−3) in Punjabi Sikhs (n = 2,819; 801 case subjects). We further replicated 66 SNPs (P < 10−4) through genotyping in a Punjabi Sikh sample (n = 2,894; 1,711 case subjects). On combined meta-analysis in Sikh populations (n = 7,329; 3,354 case subjects), we identified a novel locus in association with T2D at 13q12 represented by a directly genotyped intronic SNP (rs9552911, P = 1.82 × 10−8) in the SGCG gene. Next, we undertook in silico replication (stage 2b) of the top 513 signals (P < 10−3) in 29,157 non-Sikh South Asians (10,971 case subjects) and de novo genotyping of up to 31 top signals (P < 10−4) in 10,817 South Asians (5,157 case subjects) (stage 3b). In combined South Asian meta-analysis, we observed six suggestive associations (P < 10−5 to < 10−7), including SNPs at HMG1L1/CTCFL, PLXNA4, SCAP, and chr5p11. Further evaluation of 31 top SNPs in 33,707 East Asians (16,746 case subjects) (stage 3c) and 47,117 Europeans (8,130 case subjects) (stage 3d), and joint meta-analysis of 128,127 individuals (44,358 case subjects) from 27 multiethnic studies, did not reveal any additional loci nor was there any evidence of replication for the new variant. Our findings provide new evidence on the presence of a population-specific signal in relation to T2D, which may provide additional insights into T2D pathogenesis.
PMCID: PMC3636649  PMID: 23300278
3.  Transgenic Insulin-like Growth Factor-1 stimulates activation of COX-2 signaling in mammary glands 
Molecular carcinogenesis  2011;51(12):973-983.
Studies show that elevated IGF-1 levels are associated with an increased risk of breast cancer; however, mechanisms through which IGF-1 promotes mammary tumorigenesis in vivo have not been fully elucidated. To assess the possible involvement of COX-2 signaling in the protumorigenic effects of IGF-1 in mammary glands, we used the unique BK5.IGF-1 mouse model in which transgenic (Tg) mice have significantly increased incidence of spontaneous and DMBA–induced mammary cancer compared to wild type (WT) littermates. Studies revealed that COX-2 expression was significantly increased in Tg mammary glands and tumors, compared to age-matched WTs. Consistent with this, PGE2 levels were also increased in Tg mammary glands. Analysis of expression of the EP receptors that mediate the effects of PGE2 showed that among the four G-protein-coupled receptors, EP3 expression was elevated in Tg glands. Up-regulation of the COX-2/PGE2/EP3 pathway was accompanied by increased expression of VEGF and a striking enhancement of angiogenesis in IGF-1 Tg mammary glands. Treatment with celecoxib, a selective COX-2 inhibitor, caused a 45% reduction in mammary PGE2 levels, attenuated the influx of mast cells and reduced vascularization in Tg glands. These findings indicate that the COX-2/PGE2/EP3 signaling pathway is involved in IGF-1–stimulated mammary tumorigenesis and that COX-2–selective inhibitors may be useful in the prevention or treatment of breast cancer associated with elevated IGF-1 levels in humans.
PMCID: PMC3790642  PMID: 22006370
mammary cancer; IGF-1; COX-2; stroma; transgenic mouse
4.  Genome-wide association study in people of South Asian ancestry identifies six novel susceptibility loci for type 2 diabetes 
Nature genetics  2011;43(10):984-989.
We carried out a genome wide association study of type-2 diabetes (T2D) amongst 20,119 people of South Asian ancestry (5,561 with T2D); we identified 20 independent SNPs associated with T2D at P<10−4 for testing amongst a further 38,568 South Asians (13,170 with T2D). In combined analysis, common genetic variants at six novel loci (GRB14, ST6GAL1, VPS26A, HMG20A, AP3S2 and HNF4A) were associated with T2D (P=4.1×10−8 to P=1.9×10−11); SNPs at GRB14 were also associated with insulin sensitivity, and at ST6GAL1 and HNF4A with pancreatic beta-cell function respectively. Our findings provide additional insight into mechanisms underlying T2D, and demonstrate the potential for new discovery from genetic association studies in South Asians who have increased susceptibility to T2D.
PMCID: PMC3773920  PMID: 21874001
5.  Addressing cancer health disparities using a global “biopsychosocial” approach Addressing global cancer health disparities 
Cancer  2010;116(2):264-269.
The Center for Research on Minority Health (CRMH) has translated the biopsychosocial framework to address global cancer health disparities through the integration of biological (e.g., endogenous steroids, genetic susceptibility and pesticide levels) and behavioral (e.g., dietary interventions) determinants, along with community-based research (e.g., comprehensive involvement of community advisory boards) and educational approaches (e.g., kindergarten through postgraduate training). Evidence of successful implementation of this framework includes: health disparities training for over two thousand individuals ranging from elementary to postgraduate level, and conducting transdisciplinary projects that incorporate traditional and non-traditional health professionals to examine associations between biological and non-biological determinants of health. Examples and recommendations for implementation of the biopsychosocial approach as it applies to cancer health disparities research are described.
PMCID: PMC3754835  PMID: 19924792
cancer; prevention; health disparities; minority; multi-disciplinary; transdisciplinary; biopsychosocial; education
6.  P53 genotype as a determinant of ER expression and tamoxifen response in the MMTV-Wnt-1 model of mammary carcinogenesis 
Clinical studies show that estrogen receptor-α (ER) expressing tumors tend to have better prognosis, respond to antiestrogen therapy and have wild-type p53. Conversely, tumors with inactivating mutations in p53 tend to have worse outcomes and to be ER-negative and unresponsive to antihormone treatment. Previous studies from our laboratory have shown that p53 regulates ER expression transcriptionally, by binding the ER promoter and forming a complex with CARM1, CBP, c-Jun, RNA polymerase II and Sp1. In this study, the MMTV-Wnt-1 transgenic mouse model was used to demonstrate that p53 regulation of ER expression and function is not solely an in vitro phenomenon, but it is also operational in mammary tumorigenesis in vivo. The expression of ER and the ability to respond to tamoxifen were determined in mammary tumors arising in p53 wild type (WT) or p53 heterozygous (HT) animals carrying the Wnt-1 transgene. In p53 WT mice, development of ER-positive tumors was delayed by tamoxifen treatment, while tumors arising in p53 HT mice had significantly reduced levels of ER and were not affected by tamoxifen. P53 null tumors were also found in the p53 HT mice and these tumors were ER-negative. ER expression was upregulated in mouse mammary tumor cell lines following transfection with WT p53 or treatment with doxorubicin. These data demonstrate that p53 regulates ER expression in vivo, and affects response to tamoxifen. Results also provide an explanation for the concordant relationship between these prognostic proteins in human breast tumors.
PMCID: PMC3202603  PMID: 21191649
p53; Estrogen receptor; MMTV-Wnt-1; Tamoxifen; Breast cancer; Mammary cancer
7.  BRCA2 Variants and cardiovascular disease in a multi-ethnic study 
BMC Medical Genetics  2012;13:56.
Germline mutations of BRCA1/2 are associated with hereditary breast and ovarian cancer. Recent data suggests excess mortality in mutation carriers beyond that conferred by neoplasia, and recent in vivo and in vitro studies suggest a modulatory role for BRCA proteins in endothelial and cardiomyocyte function. We therefore tested the association of BRCA2 variants with clinical cardiovascular disease (CVD).
Using data from 1,170 individuals included in two multi-ethnic population-based studies (SHARE and SHARE-AP), the association between BRCA2 variants and CVD was evaluated. 15 SNPs in BRCA2 with minor allele frequencies (MAF) > 0.01 had been previously genotyped using the cardiovascular gene-centric 50 k SNP array. 115 individuals (9.8%) reported a CVD event, defined as myocardial infarction (MI), angina, silent MI, stroke, and angioplasty or coronary artery bypass surgery. Analyses were adjusted for age and sex. The SNPs rs11571836 and rs1799943 were subsequently genotyped using the MassARRAY platform in 1,045 cases of incident MI and 1,135 controls from the South Asian subset of an international case-control study of acute MI (INTERHEART), and rs11571836 was imputed in 4,686 cases and 4500 controls from the Pakistan Risk of Myocardial Infarction Study (PROMIS).
Two BRCA2 SNPs, rs11571836 and rs1799943, both located in untranslated regions, were associated with lower risk of CVD (OR 0.47 p = 0.01 and OR 0.56 p = 0.03 respectively) in the SHARE studies. Analysis by specific ethnicities demonstrated an association with CVD for both SNPs in Aboriginal People, and for rs11571836 only in South Asians. No association was observed in the European and Chinese subgroups. A non-significant trend towards an association between rs11571836 and lower risk of MI was observed in South Asians from INTERHEART [OR = 0.87 (95% CI: 0.75-1.01) p = 0.068], but was not evident in PROMIS [OR = 0.96 (95% CI: 0.90-1.03) p = 0.230]. Meta-analysis of both case-control studies resulted in a combined OR of 0.94 (95% CI: 0.89-1.004, p = 0.06).
Although there was an association between two SNPs in BRCA2 and CVD in a multi-ethnic population, these results were not replicated in two South Asian case-control studies of incident MI. Future studies exploring the association between BRCA variants and cardiovascular disorders are needed to clarify the role, if any, for BRCA variants in CVD pathogenesis.
PMCID: PMC3464815  PMID: 22809218
8.  Field Longevity of a Fluorescent Protein Marker in an Engineered Strain of the Pink Bollworm, Pectinophora gossypiella (Saunders) 
PLoS ONE  2012;7(6):e38547.
The cotton pest, pink bollworm (Pectinophora gossypiella (Saunders)), is a significant pest in most cotton-growing areas around the world. In southwestern USA and northern Mexico, pink bollworm is the target of the sterile insect technique (SIT), which relies on the mass-release of sterile pink bollworm adults to over-flood the wild population and thereby reduce it over time. Sterile moths reared for release are currently marked with a dye provided in their larval diet. There are concerns, however, that this marker fails from time to time, leading to sterile moths being misidentified in monitoring traps as wild moths. This can lead to expensive reactionary releases of sterile moths. We have developed a genetically marked strain that is engineered to express a fluorescent protein, DsRed2, which is easily screened under a specialised microscope. In order to test this marker under field conditions, we placed wild-type and genetically marked moths on traps and placed them in field cages. The moths were then screened, in a double-blind fashion, for DsRed2 fluorescence at regular intervals to determine marker reliability over time. The marker was shown to be robust in very high temperatures and generally proved reliable for a week or longer. More importantly, genotyping of moths on traps by PCR screening of the moths was 100% correct. Our findings indicate that this strain - and fluorescent protein markers in general - could make a valuable contribution to SIT.
PMCID: PMC3367927  PMID: 22693645
9.  Neighborhood-Level Factors Associated with Physical Dating Violence Perpetration: Results of a Representative Survey Conducted in Boston, MA 
Neighborhood-level characteristics have been found to be associated with different forms of interpersonal violence, but studies of the relationship between these characteristics and adolescent dating violence are limited. We examined 6 neighborhood-level factors in relation to adolescent physical dating violence perpetration using both adolescent and adult assessments of neighborhood characteristics, each of which was aggregated across respondents to the neighborhood level. Data came from an in-school survey of 1,530 public high school students and a random-digit-dial telephone survey of 1,710 adult residents of 38 neighborhoods in Boston. Approximately 14.3% of the youth sample reported one or more acts of physical aggression toward a dating partner in the month preceding the survey. We calculated the odds of past-month physical dating violence by each neighborhood-level factor, adjusting for school clustering, gender, race, and nativity. In our first 6 models, we used the adolescent assessment of neighborhood factors and then repeated our procedures using the adult assessment data. Using the adolescent assessment data, lower collective efficacy (AOR = 1.95, 95% CI = 1.09–3.52), lower social control (AOR = 1.92, 95% CI = 1.07–3.43), and neighborhood disorder (AOR = 1.19, 95% CI = 1.05–1.35) were each associated with increased likelihood of physical dating violence perpetration. However, when we used the adult version of the neighborhood assessment data, no neighborhood factor predicted dating violence. The implications and limitations of these findings are discussed.
PMCID: PMC3079028  PMID: 21331747
Neighborhood factors; Dating abuse; Dating violence; Partner violence; Collective efficacy; Youth violence
10.  Generalized Additive Models and Inflated Type I Error Rates of Smoother Significance Tests 
Generalized additive models (GAMs) have distinct advantages over generalized linear models as they allow investigators to make inferences about associations between outcomes and predictors without placing parametric restrictions on the associations. The variable of interest is often smoothed using a locally weighted regression (LOESS) and the optimal span (degree of smoothing) can be determined by minimizing the Akaike Information Criterion (AIC). A natural hypothesis when using GAMs is to test whether the smoothing term is necessary or if a simpler model would suffice. The statistic of interest is the difference in deviances between models including and excluding the smoothed term. As approximate chi-square tests of this hypothesis are known to be biased, permutation tests are a reasonable alternative. We compare the type I error rates of the chi-square test and of three permutation test methods using synthetic data generated under the null hypothesis. In each permutation method a distribution of differences in deviances is obtained from 999 permuted datasets and the null hypothesis is rejected if the observed statistic falls in the upper 5% of the distribution. One test is a conditional permutation test using the optimal span size for the observed data; this span size is held constant for all permutations. This test is shown to have an inflated type I error rate. Alternatively, the span size can be fixed a priori such that the span selection technique is not reliant on the observed data. This test is shown to be unbiased; however, the choice of span size is not clear. A third method is an unconditional permutation test where the optimal span size is selected for observed and permuted datasets. This test is unbiased though computationally intensive.
PMCID: PMC2952638  PMID: 20948974
Generalized Additive Models; Type I Error; Permutation Test; Span Size Selection
11.  Developmental stage determines estrogen receptor alpha expression and non-genomic mechanisms that control IGF-1 signaling and mammary proliferation in mice 
Insulin like growth factor–1 (IGF-1) stimulates increased proliferation and survival of mammary epithelial cells and also promotes mammary tumorigenesis. To study the effects of IGF-1 on the mammary gland in vivo, we used BK5.IGF-1 transgenic (Tg) mice. In these mice, IGF-1 overexpression is controlled by the bovine keratin 5 promoter and recapitulates the paracrine exposure of breast epithelium to stromal IGF-1 that is seen in women. Studies have shown that BK5.IGF-1 Tg mice are more susceptible to mammary tumorigenesis than wild-type littermates. Investigation of the mechanisms underlying increased mammary cancer risk, reported here, revealed that IGF-1 preferentially activated the PI3K/Akt pathway in glands from prepubertal Tg mice, resulting in increased cyclin D1 expression and hyperplasia. However, in glands from postpubertal Tg mice, a pathway switch occurred and activation of the Ras/Raf/MAPK pathway predominated, without increased cyclin D1 expression or proliferation. We further showed that in prepubertal Tg glands, signaling was mediated by formation of an ERα/IRS-1 complex, which activated IRS-1 and directed signaling via the PI3K/Akt pathway. Conversely, in postpubertal Tg glands, reduced ERα expression failed to stimulate formation of the ERα/IRS-1 complex, allowing signaling to proceed via the alternate Ras/Raf/MAPK pathway. These in vivo data demonstrate that changes in ERα expression at different stages of development direct IGF-1 signaling and the resulting tissue responses. As ERα levels are elevated during the prepubertal and postmenopausal stages, these may represent windows of susceptibility during which increased IGF-1 exposure maximally enhances breast cancer risk.
PMCID: PMC3248275  PMID: 22182837
12.  Maternal Depression, Perceptions of Children’s Social Aptitude, and Reported Activity Restriction among former Very Low Birth Weight Infants 
Archives of disease in childhood  2010;95(7):521-525.
Maternal depression is common among mothers of very low birth weight (VLBW) infants. In a cohort of mother-VLBW infant dyads followed to preschool age, we assessed the impact of maternal depression on mothers’ perceptions of their children’s social aptitude, and reported participation in age-appropriate preschool activities.
Longitudinal multivariable analysis of a nationally representative sample of VLBW infants in the United States. Models were adjusted for children’s developmental abilities according to the Bayley Scales of Infant Development, Mental Development Index.
800 VLBW singletons (mean gestational age 28.9 weeks) were analyzed. During the preschool years, depressed mothers perceived their children’s social abilities more negatively than non-depressed mothers. Specifically, they saw their children as less likely to be able to share with others (aOR 0.37, 95% CI 0.14, 0.96), make friends (aOR 0.58 95% CI, 0.35, 0.96), or play independently (aOR 0.30 95% CI, 0.16, 0.58). These negative perceptions were not shared by the children’s preschool teachers. Children of depressed mothers were also less likely to participate in age-appropriate preschool activities (aOR 0.30 95% CI, 0.16, 0.58). Each of these associations either lost significance or were substantially attenuated in a separate population of former healthy term infants.
Among former VLBW infants, maternal depression is associated with negative perceptions of children’s social abilities and decreased participation in preschool activities. Maternal mental health should be considered in ongoing efforts to maximize the social-emotional development of preterm infants.
PMCID: PMC3158425  PMID: 20522473
prematurity; maternal depression; vulnerable child
13.  The Receipt of Special Education Services Following Elementary School Grade Retention 
To estimate the proportion of children who receive an Individualized Education Program (IEP) following grade retention in elementary school.
Descriptive analysis of a nationally representative, longitudinal cohort.
Children retained in K/1 and 3rd grade for presumed academic reasons, followed through fifth grade.
Outcome measure
Presence or absence of an IEP.
300 children retained for presumed academic reasons in K/1, and 80 in 3rd grade were included in the study. Of the K/1 retainees, 68% never received an IEP over the subsequent four to five years; of the 3rd grade retainees, 73% never received an IEP. K/1 retainees in the highest SES quintile and suburban K/1 retainees were less likely to receive an IEP than retained children in all other SES quintiles (aOR 0.17; 95% CI 0.05-0.62) and in rural communities (aOR 0.16; 95% CI 0.06-0.44), respectively. Among K/1 retainees with persistent low academic achievement in reading and math (as assessed by standardized testing), 37% and 28%, respectively, never received an IEP.
The majority of children retained in K/1 or 3rd grade for academic reasons, including a many of those who demonstrate sustained academic difficulties, never receive an IEP during elementary school. Further studies are important to elucidate whether retained elementary school children are being denied their rights to special education services. In the meantime, early grade retention may provide an opportunity for pediatricians to help families advocate for appropriate special education evaluations for children experiencing school difficulties.
PMCID: PMC3154013  PMID: 19487611
grade retention; individualized education program; special education; school readiness
14.  Transcriptional Regulation of Estrogen Receptor-α by p53 in Human Breast Cancer Cells 
Cancer research  2009;69(8):3405-3414.
Estrogen receptor α (ER) and p53 are critical prognostic indicators in breast cancer. Loss of functional p53 is correlated with poor prognosis, ER negativity and resistance to antiestrogen treatment. Previously, we found that p53 genotype was correlated with ER expression and response to tamoxifen in mammary tumors arising in MMTV-Wnt-1 transgenic mice. These results lead us to hypothesize that p53 may regulate ER expression. To test this, MCF-7 cells were treated with doxorubicin or ionizing radiation, both of which stimulated a 5-fold increase in p53 expression. ER expression was also increased 4-fold over a 24 hour time frame. In cells treated with siRNA targeting p53, expression of both p53 and ER was significantly reduced (>60%) by 24 hours. Induction of ER by DNA-damaging agents was p53-dependent as either IR or dox failed to upregulate ER after treatment with p53-targeting siRNA. To further investigate whether p53 directly regulates transcription of the ER gene promoter, MCF-7 cells were transiently transfected with a wild type (WT) p53 expression vector along with a luciferase reporter containing the proximal promoter of ER. In cells transfected with WT p53, transcription from the ER promoter was increased 8-fold. Chromatin immunoprecipitation assays showed that p53 was recruited to the ER promoter along with CARM1, CBP, c-Jun and Sp1 and that this multifactor complex was formed in a p53-dependent manner. These data demonstrate that p53 regulates ER expression through transcriptional control of the ER promoter, accounting for their concordant expression in human breast cancer.
PMCID: PMC3079369  PMID: 19351845
Breast Cancer; Estrogen Receptor; p53
15.  Exercise Effects on Tumorigenesis in a p53-deficient Mouse Model of Breast Cancer 
Physically active women have a reduced risk of breast cancer, but the dose of activity necessary and the role of energy balance and other potential mechanisms have not been fully explored in animal models. We examined treadmill and wheel running effects on mammary tumorigenesis and biomarkers in p53-deficient (p53+/−): MMTV-Wnt-1 transgenic mice.
Female mice (9 wks old) were randomly assigned to the following groups in Experiment 1: treadmill exercise 5 d/wk, 45 min/d, 5% grade at 20 m/min, ~0.90 km/d (TREX1, n=20); at 24 m/min, ~1.08 km/d (TREX2, n=21); or a non-exercise control (CON-TREX, n=22). In Experiment 2, mice were randomly assigned to voluntary wheel-running (WHL, n=21, 2.46 ± 1.11 km/d (mean ± SD)) or a non-exercise control (CON-WHL, n=22). Body composition was measured at ~9 weeks and serum insulin-like growth factor-1 (IGF-1) at 2–3 monthly time points beginning at ~9 weeks on study. Mice were sacrificed when tumors reached 1.5 cm, mice became moribund, or there was only one mouse per treatment group remaining.
TREX1 (24 wks) and TREX2 (21 wks) had shorter survival median survival times than CON-TREX (34 wks; p<0.01); WHL and CON-WHL survival was similar (23 vs. 24 wks; p=0.32). TREX2 had increased multiplicity of mammary gland carcinomas compared to CON-TREX; WHL had a higher tumor incidence than CON-WHL. All exercising animals were lighter than their respective controls, and WHL had lower body fat than CON-WHL (p<0.01). There was no difference in IGF-1 between groups (p>0.05).
Despite beneficial or no effects on body weight, body fat, or IGF-1, exercise had detrimental effects on tumorigenesis in this p53-deficient mouse model of spontaneous mammary cancer.
PMCID: PMC3040490  PMID: 19568200
physical activity; mammary; IGF-1; body composition
16.  A power comparison of generalized additive models and the spatial scan statistic in a case-control setting 
A common, important problem in spatial epidemiology is measuring and identifying variation in disease risk across a study region. In application of statistical methods, the problem has two parts. First, spatial variation in risk must be detected across the study region and, second, areas of increased or decreased risk must be correctly identified. The location of such areas may give clues to environmental sources of exposure and disease etiology. One statistical method applicable in spatial epidemiologic settings is a generalized additive model (GAM) which can be applied with a bivariate LOESS smoother to account for geographic location as a possible predictor of disease status. A natural hypothesis when applying this method is whether residential location of subjects is associated with the outcome, i.e. is the smoothing term necessary? Permutation tests are a reasonable hypothesis testing method and provide adequate power under a simple alternative hypothesis. These tests have yet to be compared to other spatial statistics.
This research uses simulated point data generated under three alternative hypotheses to evaluate the properties of the permutation methods and compare them to the popular spatial scan statistic in a case-control setting. Case 1 was a single circular cluster centered in a circular study region. The spatial scan statistic had the highest power though the GAM method estimates did not fall far behind. Case 2 was a single point source located at the center of a circular cluster and Case 3 was a line source at the center of the horizontal axis of a square study region. Each had linearly decreasing logodds with distance from the point. The GAM methods outperformed the scan statistic in Cases 2 and 3. Comparing sensitivity, measured as the proportion of the exposure source correctly identified as high or low risk, the GAM methods outperformed the scan statistic in all three Cases.
The GAM permutation testing methods provide a regression-based alternative to the spatial scan statistic. Across all hypotheses examined in this research, the GAM methods had competing or greater power estimates and sensitivities exceeding that of the spatial scan statistic.
PMCID: PMC2918545  PMID: 20642827
17.  A multilevel non-hierarchical study of birth weight and socioeconomic status 
It is unclear whether the socioeconomic status (SES) of the community of residence has a substantial association with infant birth weight. We used multilevel models to examine associations of birth weight with family- and community-level SES in the Cape Cod Family Health Study. Data were collected retrospectively on births to women between 1969 and 1983 living on Cape Cod, Massachusetts. The sample included siblings born in different residences with differing community-level SES.
We used cross-classified models to account for multiple levels of correlation in a non-hierarchical data structure. We accounted for clustering at family- and community-levels. Models included extensive individual- and family-level covariates. SES variables of interest were maternal education; paternal occupation; percent adults living in poverty; percent adults with a four year college degree; community mean family income; and percent adult unemployment.
Residual correlation was detected at the family- but not the community-level. Substantial effects sizes were observed for family-level SES while smaller magnitudes were observed for community-level SES. Overall, higher SES corresponded to increased birth weight though neither family- nor community-level variables had significant associations with the outcome. In a model applied to a reduced sample that included a single child per family, enforcing a hierarchical data structure, paternal occupation was found to have a significant association with birth weight (p = 0.033). Larger effect sizes for community SES appeared in models applied to the full sample that contained limited covariates, such as those typically found on birth certificates.
Cross-classified models allowed us to include more than one child per family even when families moved between births. There was evidence of mild associations between family SES and birth weight. Stronger associations between paternal occupation and birth weight were observed in models applied to reduced samples with hierarchical data structures, illustrating consequences of excluding observations from the cross-classified analysis. Models with limited covariates showed associations of birth weight with community SES. In models adjusting for a complete set of individual- and family-level covariates, community SES was not as important.
PMCID: PMC2909180  PMID: 20618954
18.  The Relationship Between Maternal Depression, In-Home Violence, And Use Of Physical Punishment: What Is The Role Of Child Behavior? 
Archives of disease in childhood  2008;94(2):138-143.
Maternal depression and in-home violence are independently associated with the use of physical punishment on children; however, the combined impact of these factors on the practice of physical punishment is unknown, as is the extent to which their relationship to physical punishment varies with child behavior.
1) Determine the combined impact of maternal depression and violence exposure on one physical punishment practice, smacking; 2) Explore the role of child behaviors in this relationship.
Multivariable regression analysis of a nationally representative sample of US kindergarten children. Maternal depressive symptoms, violence exposure, and use of smacking as a discipline technique were measured by parent interview. Child behaviors were reported by teachers.
12,764 mother-child dyads were included in the analysis. The adjusted odds ratio (aOR) for smacking among mothers with depressive symptoms was 1.59 (95% CI 1.40, 1.80); among mothers exposed to in-home violence, 1.48 (95% CI 1.18, 1.85); among dually exposed mothers, 2.51 (95% CI 1.87, 3.37). Adjusting these models for child self-control or externalizing behavior yielded no change in these associations, and no effect modification by child behavior was detected. Among mothers reporting to smack their children, depression was associated with an increased smacking frequency (aIRR 1.12; 95% CI 1.01, 1.24); however, this association was reduced to borderline significance when adjusting the models for child self-control or externalizing behavior (aIRRs 1.10; 95% CI 1.00, 1.21). Depressed mothers who were also exposed to violence demonstrated higher rates of smacking (aIRR 1.29; 95% CI 1.09, 1.53); this remained stable when adjusting for child behaviors.
Maternal depression and violence exposure are associated with smacking as a means of punishment. The magnitude of this association is increased when depression and violence occur together. When coexistent, they also appear associated with the frequency of smacking. Child self-control and externalizing behavior do not appear to impact substantially the association between maternal depressive symptoms, violence exposure, and smacking.
PMCID: PMC2829298  PMID: 18786952
Maternal Depression; Violence; Corporal Punishment; Spanking; Smacking; Child Behavior
19.  Food Insecurity and Compensatory Feeding Practices among Urban Black Families 
Pediatrics  2008;122(4):e854-e860.
This study explored the relationship between food insecurity and compensatory maternal feeding practices that may be perceived as buffers against periodic food shortages among urban Black families.
We interviewed a convenience sample of Black mothers of children ages 2–13 years. Food security status (predictor) was assessed at the household level. Five maternal feeding practices (outcomes) were assessed. Two were based on Birch’s Child Feeding Questionnaire (CFQ): restricting access to certain desired foods and pressuring a child to eat; and 3 were derived from investigators’ clinical experience: the use of high calorie supplements, added sugar in beverages, and perceived appetite stimulants. Anthropometric data were collected from mothers and children.
278 mother-child dyads were analyzed, and 28% of these mothers reported being food insecure. Use of CFQ feeding practices was defined as the top quartile of responses. Use of nutritional supplements, defined as “at least 1–2 times monthly”, was common, ranging from 13%–25%. In logistic regression models adjusted for child age, BMI, and ethnicity and maternal BMI, mothers from food insecure households were significantly more likely to use high calorie supplements (OR, 2.1; 95% CI, 1.1–4.0) and appetite stimulants (OR, 3.2; 95% CI, 1.5–7.1). The odds of using the remaining compensatory feeding practices were elevated among food insecure households, but not reach statistical significance: adding sugars to beverages (OR, 2.1; 95% CI, 0.99–4.4), pressuring a child to eat (OR, 1.8; 95% CI, 0.98–3.2), and restricting access to certain foods (OR, 1.5; 95% CI 0.8–2.7).
Household food insecurity was independently associated with two of the five maternal compensatory feeding practices studied. Such practices may alter the feeding environment and increase the risk of overweight in children. Longitudinal research is necessary to determine how the relationship between food security and compensatory maternal feeding practices impacts child weight trajectories.
PMCID: PMC2712923  PMID: 18829783
Food insecurity; Feeding behavior; Overweight children; African American; Haitian

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