Whitney Robinson | University of North Carolina at Chapel Hill (original) (raw)

Papers by Whitney Robinson

Research paper thumbnail of Abstract PR07: Disparities in time to diagnostic follow up after screening mammography

Cancer Epidemiology Biomarkers & Prevention, 2015

Research paper thumbnail of Comparison of three age-period-cohort models of obesity prevalence in the United States

Background: There are divergent views on what constitutes a cohort effect and how it should be qu... more Background: There are divergent views on what constitutes a cohort effect and how it should be quantified and interpreted. Some age-period-cohort methods conceptualize age and period as potential confounders of the cohort effect, whereas others conceptualize cohort effects as a special form of age and period interaction. The purpose of the present study was to compare the results of three distinct age-period-cohort methods on obesity trends in the United States from 1971-2006. Methods: Data were drawn from seven cross-sectional waves of the National Health and Nutrition Examination Surveys (NHANES). Obesity was defined as BMI≥30 for adults and ≥95th percentile for children. First-order effects of age, period, and cohort were estimated using a traditional constraint-based approach to identification. Second-order effects were estimated by calculating linear contrasts, and additionally by conducting median polish analysis. Results: All three methods produced similar estimates of age an...

Research paper thumbnail of Race-associated biological differences among Luminal A breast tumors

Breast Cancer Research and Treatment, 2015

African-American (AA) women have higher breast cancer-specific mortality rates. A higher prevalen... more African-American (AA) women have higher breast cancer-specific mortality rates. A higher prevalence of the worse outcome Basal-like breast cancer subtype contributes to this, but AA women also have higher mortality even within the more favorable outcome Luminal A breast cancers. These differences may reflect treatment or health care access issues, inherent biological differences, or both. To identify potential biological differences by race among Luminal A breast cancers, gene expression data from 108 CAU and 57 AA breast tumors were analyzed. Race-associated genes were evaluated for associations with survival. Finally, expression of race- and survival-associated genes was evaluated in normal tissue of AA and CAU women. Six genes (ACOX2, MUC1, CRYBB2, PSPH, SQLE, TYMS) were differentially expressed by race among Luminal A breast cancers and were associated with survival (HR <0.8, HR >1.25). For all six genes, tumors in AA had higher expression of poor prognosis genes (CRYBB2, PSPH, SQLE, TYMS) and lower expression of good prognosis genes (ACOX2, MUC1). A score based on all six genes predicted survival in a large independent dataset (HR = 1.9 top vs. bottom quartile, 95 % CI: 1.4-2.5). For four genes, normal tissue of AA and CAU women showed similar expression (ACOX2, MUC1, SQLE, TYMS); however, the poor outcome-associated genes CRYBB2 and PSPH were more highly expressed in AA versus CAU women's normal tissue. This analysis identified gene expression differences that may contribute to mortality disparities and suggests that among Luminal A breast tumors there are biological differences between AA and CAU patients. Some of these differences (CRYBB2 and PSPH) may exist from the earliest stages of tumor development, or may even precede malignancy.

Research paper thumbnail of Abstract C84: Body size across the lifecourse and risk of breast cancer in African American women, the Carolina Breast Cancer Study

Cancer Epidemiology Biomarkers & Prevention, 2014

Research paper thumbnail of Abstract LB-292: Race-associated gene expression in tumors and breast cancer mortality disparities

Research paper thumbnail of Body mass index associated with genome-wide methylation in breast tissue

Breast cancer research and treatment, 2015

Gene expression studies indicate that body mass index (BMI) is associated with molecular pathways... more Gene expression studies indicate that body mass index (BMI) is associated with molecular pathways involved in inflammation, insulin-like growth factor activation, and other carcinogenic processes in breast tissue. The goal of this study was to determine whether BMI is associated with gene methylation in breast tissue and to identify pathways that are commonly methylated in association with high BMI. Epigenome-wide methylation profiles were determined using the Illumina HumanMethylation450 BeadChip array in the non-diseased breast tissue of 81 women undergoing breast surgery between 2009 and 2013 at the University of North Carolina Hospitals. Multivariable, robust linear regression was performed to identify methylation sites associated with BMI at a false discovery rate q value <0.05. Gene expression microarray data was used to identify which of the BMI-associated methylation sites also showed correlation with gene expression. Gene set enrichment analysis was conducted to assess w...

Research paper thumbnail of Exploring racial differences in the obesity gender gap

Annals of epidemiology, Jan 19, 2015

To investigate whether the gender gap in obesity prevalence is greater among U.S. blacks than whi... more To investigate whether the gender gap in obesity prevalence is greater among U.S. blacks than whites in a study designed to account for racial differences in socioeconomic and environmental conditions. We estimated age-adjusted, race-stratified gender gaps in obesity (% female obese - % male obese, defined as body mass index ≥30 kg/m(2)) in the National Health Interview Survey 2003 and the Exploring Health Disparities in Integrated Communities-Southwest Baltimore 2003 study (EHDIC-SWB). EHDIC-SWB is a population-based survey of 1381 adults living in two urban, low-income, racially integrated census tracts with no race difference in income. In the National Health Interview Survey, the obesity gender gap was larger in blacks than whites as follows: 7.7 percentage points (ppts; 95% confidence interval (CI): 3.4-11.9) in blacks versus -1.5 ppts (95% CI: -2.8 to -0.2) in whites. In EHDIC-SWB, the gender gap was similarly large for blacks and whites as follows: 15.3 ppts (95% CI: 8.6-22.0...

Research paper thumbnail of Associations of intergenerational education with metabolic health in USLatinos

Obesity, 2015

The purpose of this study was to examine the association of intergenerational education and count... more The purpose of this study was to examine the association of intergenerational education and country of birth with waist circumference, metabolic syndrome, and type 2 diabetes among older adult Latinos in the United States. We used cross-sectional data from the Sacramento Area Latino Study on Aging, a cohort of older adult Mexican-American Latinos (mean age = 70 years). At baseline, we measured waist circumference and assessed metabolic syndrome and diabetes according to established guidelines (N = 1,789). Participants were classified as US-born or foreign-born based on self-reported birth country. Participants reported their parents&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; education level (≥6 years vs. &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;6) and their own educational attainment (≥12 years vs. &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;12). US-born participants who achieved high adult education, regardless of their parents&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; education, had 37% lower odds of type 2 diabetes compared to US-born participants with both low parental and personal education levels [e.g., multivariable-adjusted OR (parental low/adult high) = 0.63; 95%CI = 0.40, 0.99]. Among the foreign-born, only those with both high parental and high personal education levels had 55% lower odds of large waist circumference (OR = 0.45; 95% CI = 0.23, 0.88) compared to foreign-born participants with both low parental and personal education levels. Intergenerational exposure to low education levels may increase central obesity and type 2 diabetes differentially among US-born and foreign-born Latinos.

Research paper thumbnail of Body size across the life course and risk of premenopausal and postmenopausal breast cancer in Black women, the Carolina Breast Cancer Study, 1993–2001

Cancer Causes & Control, 2014

It is believed that greater adiposity is associated with reduced risk of breast cancer in premeno... more It is believed that greater adiposity is associated with reduced risk of breast cancer in premenopausal but increased risk in postmenopausal women. However, few studies have evaluated these relationships among Black women or examined anthropometric measures other than near-diagnosis body mass index (BMI). This study investigated associations between measures of body size across the life course and breast cancer risk among Black and White women living in the US South. We used data from the Carolina Breast Cancer Study, a population-based case-control study of invasive breast cancer in North Carolina women aged 20-74 years. We assessed nine body size variables, including age 10 relative weight; age 18 BMI; adult weight gain; &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;reference&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; BMI 1 year before interview; and post-diagnosis measured BMI and abdominal obesity measures. Among premenopausal Whites, heavier childhood relative weight was associated with decreased cancer risk [odds ratio (OR) 0.48 95 % confidence interval 0.33-0.70]. Among premenopausal Blacks, greater adult waist circumference and waist-to-hip ratio (WHR) were associated with increased risk [waist OR 1.40 (1.00-1.97) and high tertile WHR OR 2.03 (1.29-3.19)], with associations for WHR in a similar direction in Whites. Among postmenopausal women, recalled body size was not associated with risk, except for increased risk associated with adult weight gain among White non-hormone therapy users. ER/PR status and hormone therapy use also modified other associations. In this population, greater adult BMI was not associated with increased breast cancer risk, but some measures of early-life body size and abdominal obesity were associated with risk.

Research paper thumbnail of Throwing Out the Baby with the Bathwater?

Research paper thumbnail of Selection bias: A missing factor in the obesity paradox debate

Research paper thumbnail of On the Causal Interpretation of Race in Regressions Adjusting for Confounding and Mediating Variables

Epidemiology, 2014

We consider several possible interpretations of the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;... more We consider several possible interpretations of the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;effect of race&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; when regressions are run with race as an exposure variable, controlling also for various confounding and mediating variables. When adjustment is made for socioeconomic status early in a person&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s life, we discuss under what contexts the regression coefficients for race can be interpreted as corresponding to the extent to which a racial inequality would remain if various socioeconomic distributions early in life across racial groups could be equalized. When adjustment is also made for adult socioeconomic status, we note how the overall racial inequality can be decomposed into the portion that would be eliminated by equalizing adult socioeconomic status across racial groups and the portion of the inequality that would remain even if adult socioeconomic status across racial groups were equalized. We also discuss a stronger interpretation of the effect of race (stronger in terms of assumptions) involving the joint effects of race-associated physical phenotype (eg, skin color), parental physical phenotype, genetic background, and cultural context when such variables are thought to be hypothetically manipulable and if adequate control for confounding were possible. We discuss some of the challenges with such an interpretation. Further discussion is given as to how the use of selected populations in examining racial disparities can additionally complicate the interpretation of the effects.

Research paper thumbnail of On the Causal Interpretation of Race

Research paper thumbnail of Rejoinder

Research paper thumbnail of Coming unmoored: Disproportionate increases in obesity prevalence among young, disadvantaged white women

Obesity, 2014

Since the 1980s, older, low-educated White women experienced an unprecedented decrease in life ex... more Since the 1980s, older, low-educated White women experienced an unprecedented decrease in life expectancy. We investigated whether a similar phenomenon was evident among younger women for obesity. Using the National Health and Nutrition Examination Survey, age-adjusted changes were estimated in the prevalence of overall and abdominal obesity (BMI ≥ 30 kg/m(2) , waist circumference &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 88 cm) between 1988-1994 and 2003-2010 among non-Hispanic White women aged 25-44 years, stratified by educational attainment (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;high school (HS), HS, some college, college degree). To address bias from secular increases in educational attainment, White women&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s changes in obesity prevalence were compared to changes among similarly educated Black women. Relative increases in overall obesity were disproportionately larger for low-educated (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;HS) compared to college-educated White women: 12.3 (95% CI: 3.1, 21.5) percentage points (ppts). For overall and abdominal obesity, general trends indicated dissimilar racial differences by educational attainment. For instance, overall obesity increased more in Blacks than Whites among college-educated (9.9 ppts) but not low-educated (-2.5 ppts) women. Contemporary young, low-educated White women showed indications of disproportionate worsening of overall obesity prevalence compared to more educated White and similarly educated Black women. Low education levels are more powerful indicators of obesity risk among contemporary White women than 30 years ago.

Research paper thumbnail of Birth cohort effects on abdominal obesity in the United States: the Silent Generation, Baby Boomers and Generation X

International journal of obesity (2005), 2013

Abdominal obesity predicts a wide range of adverse health outcomes. Over the past several decades... more Abdominal obesity predicts a wide range of adverse health outcomes. Over the past several decades, prevalence of abdominal obesity has increased markedly in industrialized countries like the United States No previous analyses, however, have evaluated whether there are birth cohort effects for abdominal obesity. Estimating cohort effects is necessary to forecast future health trends and understand the past population-level trends. This analysis evaluated whether there were birth cohort effects for abdominal obesity for the Silent Generation (born 1925-1945), children of the Great Depression; Baby Boomers (born 1946-1964); or Generation X (born 1965-1980). Cohort effects for prevalence of abdominal obesity were estimated using the median polish method with data collected from the National Health and Nutrition Examination Survey (NHANES) between 1988 and 2008. Respondents were aged 20-74 years. After taking into account age effects and ubiquitous secular changes, the Silent Generation ...

Research paper thumbnail of Birth cohort effects among US-born adults born in the 1980s: foreshadowing future trends in US obesity prevalence

International journal of obesity (2005), 2013

Obesity prevalence stabilized in the US in the first decade of the 2000s. However, obesity preval... more Obesity prevalence stabilized in the US in the first decade of the 2000s. However, obesity prevalence may resume increasing if younger generations are more sensitive to the obesogenic environment than older generations. We estimated cohort effects for obesity prevalence among young adults born in the 1980s. Using data collected from the National Health and Nutrition Examination Survey between 1971 and 2008, we calculated obesity for respondents aged between 2 and 74 years. We used the median polish approach to estimate smoothed age and period trends; residual non-linear deviations from age and period trends were regressed on cohort indicator variables to estimate birth cohort effects. After taking into account age effects and ubiquitous secular changes, cohorts born in the 1980s had increased propensity to obesity versus those born in the late 1960s. The cohort effects were 1.18 (95% CI: 1.01, 1.07) and 1.21 (95% CI: 1.02, 1.09) for the 1979-1983 and 1984-1988 birth cohorts, respect...

Research paper thumbnail of Body Mass Index is Associated with Gene Methylation in Estrogen Receptor-Positive Breast Tumors

Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, Jan 12, 2015

Background:Although obesity is associated with breast cancer incidence and prognosis, the underly... more Background:Although obesity is associated with breast cancer incidence and prognosis, the underlying mechanisms are poorly understood. Identification of obesity-associated epigenetic changes in breast tissue may advance mechanistic understanding of breast cancer initiation and progression. The goal of this study, therefore, was to investigate associations between obesity and gene methylation in breast tumors. Methods: Using the Illumina GoldenGate Cancer I Panel, we estimated the association between body mass index (BMI) and gene methylation in 345 breast tumor samples from Phase I of the Carolina Breast Cancer Study, a population based case-control study. Multivariable linear regression was used to identify sites that were differentially methylated by BMI. Stratification by tumor estrogen receptor status was also conducted. Results: In the majority of the 935 probes analyzed (87%), the average beta value increased with obesity (BMI ≥ 30). Obesity was significantly associated with d...

Research paper thumbnail of Serum Fatty Acids and Incidence of Ischemic Stroke Among Postmenopausal Women

Stroke, 2013

Although studies have linked types of fatty acids with coronary heart disease, data on individual... more Although studies have linked types of fatty acids with coronary heart disease, data on individual fatty acids and risk of ischemic stroke are limited. We aimed to examine the associations between serum fatty acid concentrations and incidence of ischemic stroke and its subtypes. We conducted a prospective case-control study nested in the Women&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s Health Initiative Observational Study cohort of postmenopausal US women aged 50 to 79 years. Between 1993 and 2003, incident cases of ischemic stroke were matched 1:1 to controls on age, race, and length of follow-up (964 matched pairs). Conditional logistic regression was used to estimate odds ratios and 99.9% confidence intervals (CI) for ischemic stroke and its subtypes. The multivariable-adjusted odds ratios and 99.9% CI of ischemic stroke associated with a 1-SD increment in serum fatty acid concentration were 1.38 (99.9% CI, 1.05-1.83) for linoelaidic acid (18:2tt, SD=0.04%), 1.27 (99.9% CI, 1.06-1.51) for palmitic acid (16:0, SD=2.74%), 1.20 (99.9% CI, 1.01-1.43) for oleic acid (18:1n9, SD=2.32%), 0.72 (99.9% CI, 0.59-0.87) for docosapentaenoic acid (22:5n3, SD=0.18%), 0.72 (99.9% CI, 0.59-0.87) for docosahexaenoic acid (22:6n3, SD=0.91%), and 0.81 (99.9% CI, 0.67-0.98) for arachidonic acid (20:4n6, SD=2.02%). These associations were generally consistent for atherothrombotic and lacunar stroke but not cardioembolic stroke. These findings suggest that individual serum trans, saturated, and monounsaturated fatty acids are positively associated with particular ischemic stroke subtypes, whereas individual n3 and n6 polyunsaturated fatty acids are inversely associated.

Research paper thumbnail of What is a cohort effect? Comparison of three statistical methods for modeling cohort effects in obesity prevalence in the United States, 1971–2006

Social Science & Medicine, 2010

Analysts often use different conceptual definitions of a cohort effect, and therefore different s... more Analysts often use different conceptual definitions of a cohort effect, and therefore different statistical methods, which lead to differing empirical results. A definition often used in sociology assumes that cohorts have unique characteristics confounded by age and period effects, whereas epidemiologists often conceive that period and age effects interact to produce cohort effects. The present study aims to illustrate these differences by estimating age, period, and cohort (APC) effects on obesity prevalence in the U.S. from 1971 to 2006 using both conceptual approaches. Data were drawn from seven crosssectional waves of the National Health and Nutrition Examination Survey. Obesity was defined as BMI ! 30 for adults and !95th percentile for children under the age of 20. APC effects were estimated using the classic constraint-based method (first-order effects estimated and interpreted), the Holford method (first-order effects estimated but second-order effects interpreted), and median polish method (second-order effects are estimated and interpreted). Results indicated that all methods report significant age and period effects, with lower obesity prevalence in early life as well as increasing prevalence in successive surveys. Positive cohort effects for more recently born cohorts emerged based on the constraint-based model; when cohort effects were considered second-order estimates, no significant effects emerged. First-order estimates of age-period-cohort effects are often criticized because of their reliance on arbitrary constraints, but may be conceptually meaningful for sociological research questions. Second-order estimates are statistically estimable and produce conceptually meaningful results for epidemiological research questions. Age-period-cohort analysts should explicitly state the definition of a cohort effect under consideration. Our analyses suggest that the prevalence of obesity in the U.S. in the latter part of the 20th century rose across all birth cohorts, in the manner expected based on estimated age and period effects. As such, the absence or presence of cohort effects depends on the conceptual definition and therefore statistical method used.

Research paper thumbnail of Abstract PR07: Disparities in time to diagnostic follow up after screening mammography

Cancer Epidemiology Biomarkers & Prevention, 2015

Research paper thumbnail of Comparison of three age-period-cohort models of obesity prevalence in the United States

Background: There are divergent views on what constitutes a cohort effect and how it should be qu... more Background: There are divergent views on what constitutes a cohort effect and how it should be quantified and interpreted. Some age-period-cohort methods conceptualize age and period as potential confounders of the cohort effect, whereas others conceptualize cohort effects as a special form of age and period interaction. The purpose of the present study was to compare the results of three distinct age-period-cohort methods on obesity trends in the United States from 1971-2006. Methods: Data were drawn from seven cross-sectional waves of the National Health and Nutrition Examination Surveys (NHANES). Obesity was defined as BMI≥30 for adults and ≥95th percentile for children. First-order effects of age, period, and cohort were estimated using a traditional constraint-based approach to identification. Second-order effects were estimated by calculating linear contrasts, and additionally by conducting median polish analysis. Results: All three methods produced similar estimates of age an...

Research paper thumbnail of Race-associated biological differences among Luminal A breast tumors

Breast Cancer Research and Treatment, 2015

African-American (AA) women have higher breast cancer-specific mortality rates. A higher prevalen... more African-American (AA) women have higher breast cancer-specific mortality rates. A higher prevalence of the worse outcome Basal-like breast cancer subtype contributes to this, but AA women also have higher mortality even within the more favorable outcome Luminal A breast cancers. These differences may reflect treatment or health care access issues, inherent biological differences, or both. To identify potential biological differences by race among Luminal A breast cancers, gene expression data from 108 CAU and 57 AA breast tumors were analyzed. Race-associated genes were evaluated for associations with survival. Finally, expression of race- and survival-associated genes was evaluated in normal tissue of AA and CAU women. Six genes (ACOX2, MUC1, CRYBB2, PSPH, SQLE, TYMS) were differentially expressed by race among Luminal A breast cancers and were associated with survival (HR &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.8, HR &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;1.25). For all six genes, tumors in AA had higher expression of poor prognosis genes (CRYBB2, PSPH, SQLE, TYMS) and lower expression of good prognosis genes (ACOX2, MUC1). A score based on all six genes predicted survival in a large independent dataset (HR = 1.9 top vs. bottom quartile, 95 % CI: 1.4-2.5). For four genes, normal tissue of AA and CAU women showed similar expression (ACOX2, MUC1, SQLE, TYMS); however, the poor outcome-associated genes CRYBB2 and PSPH were more highly expressed in AA versus CAU women&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s normal tissue. This analysis identified gene expression differences that may contribute to mortality disparities and suggests that among Luminal A breast tumors there are biological differences between AA and CAU patients. Some of these differences (CRYBB2 and PSPH) may exist from the earliest stages of tumor development, or may even precede malignancy.

Research paper thumbnail of Abstract C84: Body size across the lifecourse and risk of breast cancer in African American women, the Carolina Breast Cancer Study

Cancer Epidemiology Biomarkers & Prevention, 2014

Research paper thumbnail of Abstract LB-292: Race-associated gene expression in tumors and breast cancer mortality disparities

Research paper thumbnail of Body mass index associated with genome-wide methylation in breast tissue

Breast cancer research and treatment, 2015

Gene expression studies indicate that body mass index (BMI) is associated with molecular pathways... more Gene expression studies indicate that body mass index (BMI) is associated with molecular pathways involved in inflammation, insulin-like growth factor activation, and other carcinogenic processes in breast tissue. The goal of this study was to determine whether BMI is associated with gene methylation in breast tissue and to identify pathways that are commonly methylated in association with high BMI. Epigenome-wide methylation profiles were determined using the Illumina HumanMethylation450 BeadChip array in the non-diseased breast tissue of 81 women undergoing breast surgery between 2009 and 2013 at the University of North Carolina Hospitals. Multivariable, robust linear regression was performed to identify methylation sites associated with BMI at a false discovery rate q value <0.05. Gene expression microarray data was used to identify which of the BMI-associated methylation sites also showed correlation with gene expression. Gene set enrichment analysis was conducted to assess w...

Research paper thumbnail of Exploring racial differences in the obesity gender gap

Annals of epidemiology, Jan 19, 2015

To investigate whether the gender gap in obesity prevalence is greater among U.S. blacks than whi... more To investigate whether the gender gap in obesity prevalence is greater among U.S. blacks than whites in a study designed to account for racial differences in socioeconomic and environmental conditions. We estimated age-adjusted, race-stratified gender gaps in obesity (% female obese - % male obese, defined as body mass index ≥30 kg/m(2)) in the National Health Interview Survey 2003 and the Exploring Health Disparities in Integrated Communities-Southwest Baltimore 2003 study (EHDIC-SWB). EHDIC-SWB is a population-based survey of 1381 adults living in two urban, low-income, racially integrated census tracts with no race difference in income. In the National Health Interview Survey, the obesity gender gap was larger in blacks than whites as follows: 7.7 percentage points (ppts; 95% confidence interval (CI): 3.4-11.9) in blacks versus -1.5 ppts (95% CI: -2.8 to -0.2) in whites. In EHDIC-SWB, the gender gap was similarly large for blacks and whites as follows: 15.3 ppts (95% CI: 8.6-22.0...

Research paper thumbnail of Associations of intergenerational education with metabolic health in USLatinos

Obesity, 2015

The purpose of this study was to examine the association of intergenerational education and count... more The purpose of this study was to examine the association of intergenerational education and country of birth with waist circumference, metabolic syndrome, and type 2 diabetes among older adult Latinos in the United States. We used cross-sectional data from the Sacramento Area Latino Study on Aging, a cohort of older adult Mexican-American Latinos (mean age = 70 years). At baseline, we measured waist circumference and assessed metabolic syndrome and diabetes according to established guidelines (N = 1,789). Participants were classified as US-born or foreign-born based on self-reported birth country. Participants reported their parents&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; education level (≥6 years vs. &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;6) and their own educational attainment (≥12 years vs. &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;12). US-born participants who achieved high adult education, regardless of their parents&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; education, had 37% lower odds of type 2 diabetes compared to US-born participants with both low parental and personal education levels [e.g., multivariable-adjusted OR (parental low/adult high) = 0.63; 95%CI = 0.40, 0.99]. Among the foreign-born, only those with both high parental and high personal education levels had 55% lower odds of large waist circumference (OR = 0.45; 95% CI = 0.23, 0.88) compared to foreign-born participants with both low parental and personal education levels. Intergenerational exposure to low education levels may increase central obesity and type 2 diabetes differentially among US-born and foreign-born Latinos.

Research paper thumbnail of Body size across the life course and risk of premenopausal and postmenopausal breast cancer in Black women, the Carolina Breast Cancer Study, 1993–2001

Cancer Causes & Control, 2014

It is believed that greater adiposity is associated with reduced risk of breast cancer in premeno... more It is believed that greater adiposity is associated with reduced risk of breast cancer in premenopausal but increased risk in postmenopausal women. However, few studies have evaluated these relationships among Black women or examined anthropometric measures other than near-diagnosis body mass index (BMI). This study investigated associations between measures of body size across the life course and breast cancer risk among Black and White women living in the US South. We used data from the Carolina Breast Cancer Study, a population-based case-control study of invasive breast cancer in North Carolina women aged 20-74 years. We assessed nine body size variables, including age 10 relative weight; age 18 BMI; adult weight gain; &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;reference&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; BMI 1 year before interview; and post-diagnosis measured BMI and abdominal obesity measures. Among premenopausal Whites, heavier childhood relative weight was associated with decreased cancer risk [odds ratio (OR) 0.48 95 % confidence interval 0.33-0.70]. Among premenopausal Blacks, greater adult waist circumference and waist-to-hip ratio (WHR) were associated with increased risk [waist OR 1.40 (1.00-1.97) and high tertile WHR OR 2.03 (1.29-3.19)], with associations for WHR in a similar direction in Whites. Among postmenopausal women, recalled body size was not associated with risk, except for increased risk associated with adult weight gain among White non-hormone therapy users. ER/PR status and hormone therapy use also modified other associations. In this population, greater adult BMI was not associated with increased breast cancer risk, but some measures of early-life body size and abdominal obesity were associated with risk.

Research paper thumbnail of Throwing Out the Baby with the Bathwater?

Research paper thumbnail of Selection bias: A missing factor in the obesity paradox debate

Research paper thumbnail of On the Causal Interpretation of Race in Regressions Adjusting for Confounding and Mediating Variables

Epidemiology, 2014

We consider several possible interpretations of the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;... more We consider several possible interpretations of the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;effect of race&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot; when regressions are run with race as an exposure variable, controlling also for various confounding and mediating variables. When adjustment is made for socioeconomic status early in a person&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s life, we discuss under what contexts the regression coefficients for race can be interpreted as corresponding to the extent to which a racial inequality would remain if various socioeconomic distributions early in life across racial groups could be equalized. When adjustment is also made for adult socioeconomic status, we note how the overall racial inequality can be decomposed into the portion that would be eliminated by equalizing adult socioeconomic status across racial groups and the portion of the inequality that would remain even if adult socioeconomic status across racial groups were equalized. We also discuss a stronger interpretation of the effect of race (stronger in terms of assumptions) involving the joint effects of race-associated physical phenotype (eg, skin color), parental physical phenotype, genetic background, and cultural context when such variables are thought to be hypothetically manipulable and if adequate control for confounding were possible. We discuss some of the challenges with such an interpretation. Further discussion is given as to how the use of selected populations in examining racial disparities can additionally complicate the interpretation of the effects.

Research paper thumbnail of On the Causal Interpretation of Race

Research paper thumbnail of Rejoinder

Research paper thumbnail of Coming unmoored: Disproportionate increases in obesity prevalence among young, disadvantaged white women

Obesity, 2014

Since the 1980s, older, low-educated White women experienced an unprecedented decrease in life ex... more Since the 1980s, older, low-educated White women experienced an unprecedented decrease in life expectancy. We investigated whether a similar phenomenon was evident among younger women for obesity. Using the National Health and Nutrition Examination Survey, age-adjusted changes were estimated in the prevalence of overall and abdominal obesity (BMI ≥ 30 kg/m(2) , waist circumference &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt; 88 cm) between 1988-1994 and 2003-2010 among non-Hispanic White women aged 25-44 years, stratified by educational attainment (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;high school (HS), HS, some college, college degree). To address bias from secular increases in educational attainment, White women&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s changes in obesity prevalence were compared to changes among similarly educated Black women. Relative increases in overall obesity were disproportionately larger for low-educated (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;HS) compared to college-educated White women: 12.3 (95% CI: 3.1, 21.5) percentage points (ppts). For overall and abdominal obesity, general trends indicated dissimilar racial differences by educational attainment. For instance, overall obesity increased more in Blacks than Whites among college-educated (9.9 ppts) but not low-educated (-2.5 ppts) women. Contemporary young, low-educated White women showed indications of disproportionate worsening of overall obesity prevalence compared to more educated White and similarly educated Black women. Low education levels are more powerful indicators of obesity risk among contemporary White women than 30 years ago.

Research paper thumbnail of Birth cohort effects on abdominal obesity in the United States: the Silent Generation, Baby Boomers and Generation X

International journal of obesity (2005), 2013

Abdominal obesity predicts a wide range of adverse health outcomes. Over the past several decades... more Abdominal obesity predicts a wide range of adverse health outcomes. Over the past several decades, prevalence of abdominal obesity has increased markedly in industrialized countries like the United States No previous analyses, however, have evaluated whether there are birth cohort effects for abdominal obesity. Estimating cohort effects is necessary to forecast future health trends and understand the past population-level trends. This analysis evaluated whether there were birth cohort effects for abdominal obesity for the Silent Generation (born 1925-1945), children of the Great Depression; Baby Boomers (born 1946-1964); or Generation X (born 1965-1980). Cohort effects for prevalence of abdominal obesity were estimated using the median polish method with data collected from the National Health and Nutrition Examination Survey (NHANES) between 1988 and 2008. Respondents were aged 20-74 years. After taking into account age effects and ubiquitous secular changes, the Silent Generation ...

Research paper thumbnail of Birth cohort effects among US-born adults born in the 1980s: foreshadowing future trends in US obesity prevalence

International journal of obesity (2005), 2013

Obesity prevalence stabilized in the US in the first decade of the 2000s. However, obesity preval... more Obesity prevalence stabilized in the US in the first decade of the 2000s. However, obesity prevalence may resume increasing if younger generations are more sensitive to the obesogenic environment than older generations. We estimated cohort effects for obesity prevalence among young adults born in the 1980s. Using data collected from the National Health and Nutrition Examination Survey between 1971 and 2008, we calculated obesity for respondents aged between 2 and 74 years. We used the median polish approach to estimate smoothed age and period trends; residual non-linear deviations from age and period trends were regressed on cohort indicator variables to estimate birth cohort effects. After taking into account age effects and ubiquitous secular changes, cohorts born in the 1980s had increased propensity to obesity versus those born in the late 1960s. The cohort effects were 1.18 (95% CI: 1.01, 1.07) and 1.21 (95% CI: 1.02, 1.09) for the 1979-1983 and 1984-1988 birth cohorts, respect...

Research paper thumbnail of Body Mass Index is Associated with Gene Methylation in Estrogen Receptor-Positive Breast Tumors

Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology, Jan 12, 2015

Background:Although obesity is associated with breast cancer incidence and prognosis, the underly... more Background:Although obesity is associated with breast cancer incidence and prognosis, the underlying mechanisms are poorly understood. Identification of obesity-associated epigenetic changes in breast tissue may advance mechanistic understanding of breast cancer initiation and progression. The goal of this study, therefore, was to investigate associations between obesity and gene methylation in breast tumors. Methods: Using the Illumina GoldenGate Cancer I Panel, we estimated the association between body mass index (BMI) and gene methylation in 345 breast tumor samples from Phase I of the Carolina Breast Cancer Study, a population based case-control study. Multivariable linear regression was used to identify sites that were differentially methylated by BMI. Stratification by tumor estrogen receptor status was also conducted. Results: In the majority of the 935 probes analyzed (87%), the average beta value increased with obesity (BMI ≥ 30). Obesity was significantly associated with d...

Research paper thumbnail of Serum Fatty Acids and Incidence of Ischemic Stroke Among Postmenopausal Women

Stroke, 2013

Although studies have linked types of fatty acids with coronary heart disease, data on individual... more Although studies have linked types of fatty acids with coronary heart disease, data on individual fatty acids and risk of ischemic stroke are limited. We aimed to examine the associations between serum fatty acid concentrations and incidence of ischemic stroke and its subtypes. We conducted a prospective case-control study nested in the Women&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s Health Initiative Observational Study cohort of postmenopausal US women aged 50 to 79 years. Between 1993 and 2003, incident cases of ischemic stroke were matched 1:1 to controls on age, race, and length of follow-up (964 matched pairs). Conditional logistic regression was used to estimate odds ratios and 99.9% confidence intervals (CI) for ischemic stroke and its subtypes. The multivariable-adjusted odds ratios and 99.9% CI of ischemic stroke associated with a 1-SD increment in serum fatty acid concentration were 1.38 (99.9% CI, 1.05-1.83) for linoelaidic acid (18:2tt, SD=0.04%), 1.27 (99.9% CI, 1.06-1.51) for palmitic acid (16:0, SD=2.74%), 1.20 (99.9% CI, 1.01-1.43) for oleic acid (18:1n9, SD=2.32%), 0.72 (99.9% CI, 0.59-0.87) for docosapentaenoic acid (22:5n3, SD=0.18%), 0.72 (99.9% CI, 0.59-0.87) for docosahexaenoic acid (22:6n3, SD=0.91%), and 0.81 (99.9% CI, 0.67-0.98) for arachidonic acid (20:4n6, SD=2.02%). These associations were generally consistent for atherothrombotic and lacunar stroke but not cardioembolic stroke. These findings suggest that individual serum trans, saturated, and monounsaturated fatty acids are positively associated with particular ischemic stroke subtypes, whereas individual n3 and n6 polyunsaturated fatty acids are inversely associated.

Research paper thumbnail of What is a cohort effect? Comparison of three statistical methods for modeling cohort effects in obesity prevalence in the United States, 1971–2006

Social Science & Medicine, 2010

Analysts often use different conceptual definitions of a cohort effect, and therefore different s... more Analysts often use different conceptual definitions of a cohort effect, and therefore different statistical methods, which lead to differing empirical results. A definition often used in sociology assumes that cohorts have unique characteristics confounded by age and period effects, whereas epidemiologists often conceive that period and age effects interact to produce cohort effects. The present study aims to illustrate these differences by estimating age, period, and cohort (APC) effects on obesity prevalence in the U.S. from 1971 to 2006 using both conceptual approaches. Data were drawn from seven crosssectional waves of the National Health and Nutrition Examination Survey. Obesity was defined as BMI ! 30 for adults and !95th percentile for children under the age of 20. APC effects were estimated using the classic constraint-based method (first-order effects estimated and interpreted), the Holford method (first-order effects estimated but second-order effects interpreted), and median polish method (second-order effects are estimated and interpreted). Results indicated that all methods report significant age and period effects, with lower obesity prevalence in early life as well as increasing prevalence in successive surveys. Positive cohort effects for more recently born cohorts emerged based on the constraint-based model; when cohort effects were considered second-order estimates, no significant effects emerged. First-order estimates of age-period-cohort effects are often criticized because of their reliance on arbitrary constraints, but may be conceptually meaningful for sociological research questions. Second-order estimates are statistically estimable and produce conceptually meaningful results for epidemiological research questions. Age-period-cohort analysts should explicitly state the definition of a cohort effect under consideration. Our analyses suggest that the prevalence of obesity in the U.S. in the latter part of the 20th century rose across all birth cohorts, in the manner expected based on estimated age and period effects. As such, the absence or presence of cohort effects depends on the conceptual definition and therefore statistical method used.