Bio

Bio


I am interested in using statistical methods to understand and improve human health. I currently collaborate with investigators in the medical school in chronic disease prevention, pediatrics, and nutrition. I joined the Stanford Quantitative Sciences Unit in 2015 after completing my PhD in Biostatistics at the University of North Carolina at Chapel Hill. I am also interested in software development. At UNC, I wrote the R packages RI2by2 and interferenceCI to accompany papers from my dissertation, titled "Causal inference for binary data with interference". At Stanford, I helped translate the near-far matching method into an R package titled nearfar.

Education & Certifications


  • PhD, University of North Carolina, Chapel Hill, Biostatistics (2015)

Publications

All Publications


  • Network analysis: a novel method for mapping neonatal acute transport patterns in California. Journal of perinatology Kunz, S. N., Zupancic, J. A., Rigdon, J., Phibbs, C. S., Lee, H. C., Gould, J. B., Leskovec, J., Profit, J. 2017; 37 (6): 702-708

    Abstract

    The objectives of this study are to use network analysis to describe the pattern of neonatal transfers in California, to compare empirical sub-networks with established referral regions and to determine factors associated with transport outside the originating sub-network.This cross-sectional database study included 6546 infants <28 days old transported within California in 2012. After generating a graph representing acute transfers between hospitals (n=6696), we used community detection techniques to identify more tightly connected sub-networks. These empirically derived sub-networks were compared with state-defined regional referral networks. Reasons for transfer between empirical sub-networks were assessed using logistic regression.Empirical sub-networks showed significant overlap with regulatory regions (P<0.001). Transfer outside the empirical sub-network was associated with major congenital anomalies (P<0.001), need for surgery (P=0.01) and insurance as the reason for transfer (P<0.001).Network analysis accurately reflected empirical neonatal transfer patterns, potentially facilitating quantitative, rather than qualitative, analysis of regionalized health care delivery systems.Journal of Perinatology advance online publication, 23 March 2017; doi:10.1038/jp.2017.20.

    View details for DOI 10.1038/jp.2017.20

    View details for PubMedID 28333155

  • Factors Associated With Provider Burnout in the NICU PEDIATRICS Tawfik, D. S., Phibbs, C. S., Sexton, J. B., Kan, P., Sharek, P. J., Nisbet, C. C., Rigdon, J., Trockel, M., Profit, J. 2017; 139 (5)

    Abstract

    NICUs vary greatly in patient acuity and volume and represent a wide array of organizational structures, but the effect of these differences on NICU providers is unknown. This study sought to test the relation between provider burnout prevalence and organizational factors in California NICUs.Provider perceptions of burnout were obtained from 1934 nurse practitioners, physicians, registered nurses, and respiratory therapists in 41 California NICUs via a validated 4-item questionnaire based on the Maslach Burnout Inventory. The relations between burnout and organizational factors of each NICU were evaluated via t-test comparison of quartiles, univariable regression, and multivariable regression.Overall burnout prevalence was 26.7% ± 9.8%. Highest burnout prevalence was found among NICUs with higher average daily admissions (32.1% ± 6.4% vs 17.2% ± 6.7%, P < .001), higher average occupancy (28.1% ± 8.1% vs 19.9% ± 8.4%, P = .02), and those with electronic health records (28% ± 11% vs 18% ± 7%, P = .03). In sensitivity analysis, nursing burnout was more sensitive to organizational differences than physician burnout in multivariable modeling, significantly associated with average daily admissions, late transfer proportion, nursing hours per patient day, and mortality per 1000 infants. Burnout prevalence showed no association with proportion of high-risk patients, teaching hospital distinction, or in-house attending presence.Burnout is most prevalent in NICUs with high patient volume and electronic health records and may affect nurses disproportionately. Interventions to reduce burnout prevalence may be of greater importance in NICUs with ≥10 weekly admissions.

    View details for DOI 10.1542/peds.2016-4134

    View details for Web of Science ID 000400371500040

    View details for PubMedID 28557756

  • Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA internal medicine Trepanowski, J. F., Kroeger, C. M., Barnosky, A., Klempel, M. C., Bhutani, S., Hoddy, K. K., Gabel, K., Freels, S., Rigdon, J., Rood, J., Ravussin, E., Varady, K. A. 2017

    Abstract

    Alternate-day fasting has become increasingly popular, yet, to date, no long-term randomized clinical trials have evaluated its efficacy.To compare the effects of alternate-day fasting vs daily calorie restriction on weight loss, weight maintenance, and risk indicators for cardiovascular disease.A single-center randomized clinical trial of obese adults (18 to 64 years of age; mean body mass index, 34) was conducted between October 1, 2011, and January 15, 2015, at an academic institution in Chicago, Illinois.Participants were randomized to 1 of 3 groups for 1 year: alternate-day fasting (25% of energy needs on fast days; 125% of energy needs on alternating "feast days"), calorie restriction (75% of energy needs every day), or a no-intervention control. The trial involved a 6-month weight-loss phase followed by a 6-month weight-maintenance phase.The primary outcome was change in body weight. Secondary outcomes were adherence to the dietary intervention and risk indicators for cardiovascular disease.Among the 100 participants (86 women and 14 men; mean [SD] age, 44 [11] years), the dropout rate was highest in the alternate-day fasting group (13 of 34 [38%]), vs the daily calorie restriction group (10 of 35 [29%]) and control group (8 of 31 [26%]). Mean weight loss was similar for participants in the alternate-day fasting group and those in the daily calorie restriction group at month 6 (-6.8% [95% CI, -9.1% to -4.5%] vs -6.8% [95% CI, -9.1% to -4.6%]) and month 12 (-6.0% [95% CI, -8.5% to -3.6%] vs -5.3% [95% CI, -7.6% to -3.0%]) relative to those in the control group. Participants in the alternate-day fasting group ate more than prescribed on fast days, and less than prescribed on feast days, while those in the daily calorie restriction group generally met their prescribed energy goals. There were no significant differences between the intervention groups in blood pressure, heart rate, triglycerides, fasting glucose, fasting insulin, insulin resistance, C-reactive protein, or homocysteine concentrations at month 6 or 12. Mean high-density lipoprotein cholesterol levels at month 6 significantly increased among the participants in the alternate-day fasting group (6.2 mg/dL [95% CI, 0.1-12.4 mg/dL]), but not at month 12 (1.0 mg/dL [95% CI, -5.9 to 7.8 mg/dL]), relative to those in the daily calorie restriction group. Mean low-density lipoprotein cholesterol levels were significantly elevated by month 12 among the participants in the alternate-day fasting group (11.5 mg/dL [95% CI, 1.9-21.1 mg/dL]) compared with those in the daily calorie restriction group.Alternate-day fasting did not produce superior adherence, weight loss, weight maintenance, or cardioprotection vs daily calorie restriction.clinicaltrials.gov Identifier: NCT00960505.

    View details for DOI 10.1001/jamainternmed.2017.0936

    View details for PubMedID 28459931

  • Teamwork in the NICU Setting and Its Association with Health Care-Associated Infections in Very Low-Birth-Weight Infants. American journal of perinatology Profit, J., Sharek, P. J., Kan, P., Rigdon, J., Desai, M., Nisbet, C. C., Tawfik, D. S., Thomas, E. J., Lee, H. C., Sexton, J. B. 2017

    Abstract

    Background and Objective Teamwork may affect clinical care in the neonatal intensive care unit (NICU) setting. The objective of this study was to assess teamwork climate across NICUs and to test scale-level and item-level associations with health care-associated infection (HAI) rates in very low-birth-weight (VLBW) infants. Methods Cross-sectional study of the association between HAI rates, defined as any bacterial or fungal infection during the birth hospitalization, among 6,663 VLBW infants cared for in 44 NICUs between 2010 and 2012. NICU HAI rates were correlated with teamwork climate ratings obtained in 2011 from 2,073 of 3,294 eligible NICU health professionals (response rate 63%). The relation between HAI rates and NICU teamwork climate was assessed using logistic regression models including NICU as a random effect. Results Across NICUs, 36 to 100% (mean 66%) of respondents reported good teamwork. HAI rates were significantly and independently associated with teamwork climate (odds ratio, 0.82; 95% confidence interval, 0.73-0.92, p = 0.005), such that the odds of an infant contracting a HAI decreased by 18% with each 10% rise in NICU respondents reporting good teamwork. Conclusion Improving teamwork may be an important element in infection control efforts.

    View details for DOI 10.1055/s-0037-1601563

    View details for PubMedID 28395366

  • Burnout in the neonatal intensive care unit and its relation to healthcare-associated infections. Journal of perinatology Tawfik, D. S., Sexton, J. B., Kan, P., Sharek, P. J., Nisbet, C. C., Rigdon, J., Lee, H. C., Profit, J. 2017; 37 (3): 315-320

    Abstract

    To examine burnout prevalence among California neonatal intensive care units (NICUs) and to test the relation between burnout and healthcare-associated infection (HAI) rates in very low birth weight (VLBW) neonates.Retrospective observational study of provider perceptions of burnout from 2073 nurse practitioners, physicians, registered nurses and respiratory therapists, using a validated four-item questionnaire based on the Maslach Burnout Inventory. The relation between burnout and HAI rates among VLBW (<1500 g) neonates from each NICU was evaluated using multi-level logistic regression analysis with patient-level factors as fixed effects.We found variable prevalence of burnout across the NICUs surveyed (mean 25.2±10.1%). Healthcare-associated infection rates were 8.3±5.1% during the study period. Highest burnout prevalence was found among nurses, nurse practitioners and respiratory therapists (non-physicians, 28±11% vs 17±19% physicians), day shift workers (30±3% vs 25±4% night shift) and workers with 5 or more years of service (29±2% vs 16±6% in fewer than 3 years group). Overall burnout rates showed no correlation with risk-adjusted rates of HAIs (r=-0.133). Item-level analysis showed positive association between HAIs and perceptions of working too hard (odds ratio 1.15, 95% confidence interval 1.04-1.28). Sensitivity analysis of high-volume NICUs suggested a moderate correlation between burnout prevalence and HAIs (r=0.34).Burnout is most prevalent among non-physicians, daytime workers and experienced workers. Perceptions of working too hard associate with increased HAIs in this cohort of VLBW infants, but overall burnout prevalence is not predictive.Journal of Perinatology advance online publication, 17 November 2016; doi:10.1038/jp.2016.211.

    View details for DOI 10.1038/jp.2016.211

    View details for PubMedID 27853320

  • DIETFITS study (diet intervention examining the factors interacting with treatment success) - Study design and methods. Contemporary clinical trials Stanton, M. V., Robinson, J. L., Kirkpatrick, S. M., Farzinkhou, S., Avery, E. C., Rigdon, J., Offringa, L. C., Trepanowski, J. F., Hauser, M. E., Hartle, J. C., Cherin, R. J., King, A. C., Ioannidis, J. P., Desai, M., Gardner, C. D. 2017; 53: 151-161

    Abstract

    Numerous studies have attempted to identify successful dietary strategies for weight loss, and many have focused on Low-Fat vs. Low-Carbohydrate comparisons. Despite relatively small between-group differences in weight loss found in most previous studies, researchers have consistently observed relatively large between-subject differences in weight loss within any given diet group (e.g., ~25kg weight loss to ~5kg weight gain). The primary objective of this study was to identify predisposing individual factors at baseline that help explain differential weight loss achieved by individuals assigned to the same diet, particularly a pre-determined multi-locus genotype pattern and insulin resistance status. Secondary objectives included discovery strategies for further identifying potential genetic risk scores. Exploratory objectives included investigation of an extensive set of physiological, psychosocial, dietary, and behavioral variables as moderating and/or mediating variables and/or secondary outcomes. The target population was generally healthy, free-living adults with BMI 28-40kg/m(2) (n=600). The intervention consisted of a 12-month protocol of 22 one-hour evening instructional sessions led by registered dietitians, with ~15-20 participants/class. Key objectives of dietary instruction included focusing on maximizing the dietary quality of both Low-Fat and Low-Carbohydrate diets (i.e., Healthy Low-Fat vs. Healthy Low-Carbohydrate), and maximally differentiating the two diets from one another. Rather than seeking to determine if one dietary approach was better than the other for the general population, this study sought to examine whether greater overall weight loss success could be achieved by matching different people to different diets. Here we present the design and methods of the study.

    View details for DOI 10.1016/j.cct.2016.12.021

    View details for PubMedID 28027950

  • Use of Gene Expression Profiling and Chemotherapy in Early-Stage Breast Cancer: A Study of Linked Electronic Medical Records, Cancer Registry Data, and Genomic Data Across Two Health Care Systems. Journal of oncology practice / American Society of Clinical Oncology Afghahi, A., Mathur, M., Thompson, C. A., Mitani, A., Rigdon, J., Desai, M., Yu, P. P., de Bruin, M. A., Seto, T., Olson, C., Kenkare, P., Gomez, S. L., Das, A. K., Luft, H. S., Sledge, G. W., Sing, A. P., Kurian, A. W. 2016; 12 (6): e697-709

    Abstract

    The 21-gene recurrence score (RS) identifies patients with breast cancer who derive little benefit from chemotherapy; it may reduce unwarranted variability in the use of chemotherapy. We tested whether the use of RS seems to guide chemotherapy receipt across different cancer care settings.We developed a retrospective cohort of patients with breast cancer by using electronic medical record data from Stanford University (hereafter University) and Palo Alto Medical Foundation (hereafter Community) linked with demographic and staging data from the California Cancer Registry and RS results from the testing laboratory (Genomic Health Inc., Redwood City, CA). Multivariable analysis was performed to identify predictors of RS and chemotherapy use.In all, 10,125 patients with breast cancer were diagnosed in the University or Community systems from 2005 to 2011; 2,418 (23.9%) met RS guidelines criteria, of whom 15.6% received RS. RS was less often used for patients with involved lymph nodes, higher tumor grade, and age < 40 or ≥ 65 years. Among RS recipients, chemotherapy receipt was associated with a higher score (intermediate v low: odds ratio, 3.66; 95% CI, 1.94 to 6.91). A total of 293 patients (10.6%) received care in both health care systems (hereafter dual use); although receipt of RS was associated with dual use (v University: odds ratio, 1.73; 95% CI, 1.18 to 2.55), there was no difference in use of chemotherapy after RS by health care setting.Although there was greater use of RS for patients who sought care in more than one health care setting, use of chemotherapy followed RS guidance in University and Community health care systems. These results suggest that precision medicine may help optimize cancer treatment across health care settings.

    View details for DOI 10.1200/JOP.2015.009803

    View details for PubMedID 27221993

    View details for PubMedCentralID PMC4957259

  • Pre-treatment non-target lung FDG-PET uptake predicts symptomatic radiation pneumonitis following Stereotactic Ablative Radiotherapy (SABR). Radiotherapy and oncology Chaudhuri, A. A., Binkley, M. S., Rigdon, J., Carter, J. N., Aggarwal, S., Dudley, S. A., Qian, Y., Kumar, K. A., Hara, W. Y., Gensheimer, M., Nair, V. S., Maxim, P. G., Shultz, D. B., Bush, K., Trakul, N., Le, Q., Diehn, M., Loo, B. W., Guo, H. H. 2016; 119 (3): 454-460

    Abstract

    To determine if pre-treatment non-target lung FDG-PET uptake predicts for symptomatic radiation pneumonitis (RP) following lung stereotactic ablative radiotherapy (SABR).We reviewed a 258 patient database from our institution to identify 28 patients who experienced symptomatic (grade ⩾ 2) RP after SABR, and compared them to 57 controls who did not develop symptomatic RP. We compared clinical, dosimetric and functional imaging characteristics between the 2 cohorts including pre-treatment non-target lung FDG-PET uptake.Median follow-up time was 26.9 months. Patients who experienced symptomatic RP had significantly higher non-target lung FDG-PET uptake as measured by mean SUV (p < 0.0001) than controls. ROC analysis for symptomatic RP revealed area under the curve (AUC) of 0.74, with sensitivity 82.1% and specificity 57.9% with cutoff mean non-target lung SUV > 0.56. Predictive value increased (AUC of 0.82) when mean non-target lung SUV was combined with mean lung dose (MLD). We developed a 0-2 point model using these 2 variables, 1 point each for SUV > 0.56 or MLD > 5.88 Gy equivalent dose in 2 Gy per fraction (EQD2), predictive for symptomatic RP in our cohort with hazard ratio 10.01 for score 2 versus 0 (p < 0.001).Patients with elevated pre-SABR non-target lung FDG-PET uptake are at increased risk of symptomatic RP after lung SABR. Our predictive model suggests patients with mean non-target lung SUV > 0.56 and MLD > 5.88 Gy EQD2 are at highest risk. Our predictive model should be validated in an external cohort before clinical implementation.

    View details for DOI 10.1016/j.radonc.2016.05.007

    View details for PubMedID 27267049

  • Exact confidence intervals in the presence of interference STATISTICS & PROBABILITY LETTERS Rigdon, J., Hudgens, M. G. 2015; 105: 130-135
  • Chromosomal copy number alterations for associations of ductal carcinoma in situ with invasive breast cancer BREAST CANCER RESEARCH Afghahi, A., Forgo, E., Mitani, A. A., Desai, M., Varma, S., Seto, T., Rigdon, J., Jensen, K. C., Troxell, M. L., Gomez, S. L., Das, A. K., Beck, A. H., Kurian, A. W., West, R. B. 2015; 17

    View details for DOI 10.1186/s13058-015-0623-y

    View details for Web of Science ID 000359348400001

    View details for PubMedID 26265211