Balasubramanian, Raji

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Associate Professor of Biostatistics, Department of Biostatistics and Epidemiology, University of Massachusetts - Amherst
Last Name
Balasubramanian
First Name
Raji
Discipline
Biostatistics
Computational Biology
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Metabolomic studies, pediatric HIV studies, measurement error in self-reported outcomes, study design, high dimensional data and analysis of biological networks
Introduction
My research into statistical methods is motivated by ongoing collaborations in large-scale epidemiological studies such as the Women’s Health Initiative. Specific research projects include the development and application of statistical models for analyzing self-reported outcomes. Other research interests include methods for metabolomics investigations and pediatric HIV clinical studies.
Prior to my academic career, I served as Director of Biostatistics at BG Medicine Inc., where I was involved in the design and analysis of several biomarker discovery studies incorporating high throughput ‘omic’ technologies.
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2011 - 20192
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    PublicationOpen Access
    Caffeinated Coffee, Decaffeinated Coffee and Endometrial Cancer Risk: A Prospective Cohort Study among US Postmenopausal Women
    (2011-01) Giri, Ayush; Sturgeon, Susan R.; Luisi, Nicole; Bertone-Johnson, Elizabeth; Balasubramanian, Raji; Reeves, Katherine W.
    There is plausible biological evidence as well as epidemiologic evidence to suggest coffee consumption may lower endometrial cancer risk. We evaluated the associations between self-reported total coffee, caffeinated coffee and decaffeinated coffee, and endometrial cancer risk using the Women’s Health Initiative Observational Study Research Materials obtained from the National Heart, Lung, and Blood Institute Biological Specimen and Data Repository Coordinating Center. Our primary analyses included 45,696 women and 427 incident endometrial cancer cases, diagnosed over a total of 342,927 person-years of follow-up. We used Cox-proportional hazard models to evaluate coffee consumption and endometrial cancer risk. Overall, we did not find an association between coffee consumption and endometrial cancer risk. Compared to non-daily drinkers (none or < 1 cup/day), the multivariable adjusted hazard ratios for women who drank ≥4 cups/day were 0.86 (95% confidence interval (CI) 0.63, 1.18) for total coffee, 0.89 (95% CI 0.63, 1.27) for caffeinated coffee, and 0.51 (95% CI 0.25, 1.03) for decaf coffee. In subgroup analyses by body mass index (BMI) there were no associations among normal-weight and overweight women for total coffee and caffeinated coffee. However among obese women, compared to the referent group (none or < 1 cup/day), the hazard ratios for women who drank ≥2 cups/day were: 0.72 (95% CI 0.50, 1.04) for total coffee and 0.66 (95% CI 0.45, 0.97) for caffeinated coffee. Hazard ratios for women who drank ≥2 cups/day for decaffeinated coffee drinkers were 0.67 (0.43–1.06), 0.93 (0.55–1.58) and 0.80 (0.49–1.30) for normal, overweight and obese women, respectively. Our study suggests that caffeinated coffee consumption may be associated with lower endometrial cancer risk among obese postmenopausal women, but the association with decaffeinated coffee remains unclear.
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    PublicationOpen Access
    Identifying Metabolomic Profiles of Insulinemic Dietary Patterns
    (2019-01) Tabung, Fred K.; Balasubramanian, Raji; Liang, Liming; Clinton, Steven K.; Cespedes Feliciano, Elizabeth M.; Manson, JoAnn E.; Horn, Linda Van; Wactawski-Wende, Jean; Clish, Clary B.; Giowanucci, Edward L.; Rexrode, Kathryn M.
    The food-based empirical dietary index for hyperinsulinemia (EDIH) score assesses the insulinemic potential of diet. This cross-sectional study evaluated associations between EDIH scores from food frequency questionnaires with c-peptide concentrations and with 448 metabolites, from fasting plasma samples, in multivariable linear regression analyses. Metabolites were measured with liquid chromatography tandem mass spectroscopy. Using a robust two-stage study design, discovery of metabolite associations was conducted among 1109 Women’s Health Initiative (WHI) Hormone Therapy (HT) trial participants and results replicated in an independent dataset of 810 WHI Observational Study (OS) participants. In both discovery and replication datasets, statistical significance was based on the false-discovery rate adjusted P < 0.05. In the multivariable-adjusted analyses, EDIH was significantly associated with c-peptide concentrations among 919 women (HT & OS) with c-peptide data. On average, c-peptide concentrations were 18% higher (95% CI, 6%, 32%; P-trend < 0.0001) in EDIH quintile 5 compared to quintile 1. Twenty-six metabolites were significantly associated with EDIH in the discovery dataset, and 19 of these were replicated in the validation dataset. Nine metabolites were found to decrease in abundance with increasing EDIH scores and included: C14:0 CE, C16:1 CE, C18:1 CE, C18:3 CE, C20:3 CE, C20:5 CE, C36:1 PS plasmalogen, trigonelline, and eicosapentanoate, whereas the 10 metabolites observed to increase with increasing EDIH scores were: C18:2 SM, C36:3 DAG, C36:4 DAG-A, C51:3 TAG, C52:3 TAG, C52:4, TAG, C54:3 TAG, C54:4 TAG, C54:6 TAG, and C10:2 carnitine. Cholesteryl esters, phospholipids, acylglycerols, and acylcarnitines may constitute circulating metabolites that are associated with insulinemic dietary patterns.