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Photo of Dr. Ravi Varadhan

Ravi Varadhan, PhD

Assistant Professor
Associate Professor of Medicine
Male

Titles

  • Assistant Professor
  • Associate Professor of Medicine

Centers & Institutes

  • Center on Aging and Health

Research Interests

Development and translation of statistical methodology for patient-centered outcomes research; Development of modeling approaches for studying the etiology of geriatric frailty; Development of efficient computational algorithms and sof

Biography

Dr. Varadhan is a highly-trained mathematical modeler with a PhD in Environmental Engineering from the University of Toledo and another PhD in Biostatistics from Johns Hopkins. He is a co-director for the Biostatistics and Epidemiology of Aging Training Program. He has published numerous articles in engineering, environmental science, applied mathematics, statistics, epidemiology, gerontology, and biomedical journals. He has been invited to present his novel methods in patient-centered outcomes research at the biennial Symposia organized by the Agency for Healthcare Research and Quality in 2009 and 2011.

Languages

  • English
Additional Resources +
  • Education +

    Education

    • Ph.D, University of Toledo, Environmental Engineering
    • Ph.D, Johns Hopkins University, Baltimore, MD, Biostatistics
  • Research & Publications +

    Research Summary

    Dr. Varadhan’s research focuses on the development and application of mathematical approaches for characterizing the homeostatic impairments underlying the geriatric syndrome of frailty, which increases the risk of disability and mortality. His work seeks to characterize frailty as a physiological state of vulnerability to stressors, by observing and modeling the dynamic response of multiple physiological systems to different stressors. Particular challenges in his research paradigm are: (a) the design of stress-response experiments that are population-based, and that can be implemented with minimal burden on frail, older adults, and (b) the development of mathematical modeling approaches that can handle diverse types of response data, and that can incorporate confounding factors and inter-person heterogeneity.

    His other important research interests include (a) the development of computational techniques to accelerate the EM algorithm, a popular computational approach in statistics, and (b) the development and application of flexible regression modeling approaches for risk-factor etiology and for prediction in observational studies of geriatric syndromes.

    Selected Publications

    Varadhan R, Gilbert P.  BB: An R Package for Solving a Large System of Nonlinear Equations and for Optimizing a High-Dimensional Nonlinear Objective Function. J Stat Soft. 2009 Oct;32(4):1-26.

    Varadhan R, Chaves PH, Lipsitz LA, Stein PK, Tian J, Windham BG, Berger RD,Fried LP. Frailty and impaired cardiac autonomic control: new insights fromprincipal components aggregation of traditional heart rate variability indices. JGerontol A Biol Sci Med Sci. 2009 Jun;64(6):682-7. Epub 2009 Feb 17.
    View on Pubmed

    Alipanah N, Varadhan R, Sun K, Ferrucci L, Fried LP, Semba RD. Low serum carotenoids are associated with a decline in walking speed in older women. J NutrHealth Aging. 2009 Mar;13(3):170-5.
    View on Pubmed

    Fried LP, Xue QL, Cappola AR, Ferrucci L, Chaves P, Varadhan R, Guralnik JM, Leng SX, Semba RD, Walston JD, Blaum CS, Bandeen-Roche K. Nonlinear Multisystem Physiological Dysregulation Associated With Frailty in Older Women: Implications for Etiology and Treatment. J Gerontol A Biol Sci Med Sci. 2009 Jul 21. [Epub ahead of print].
    View on Pubmed

    Chaves PH, Varadhan R, Lipsitz LA, Stein PK, Windham BG, Tian J, Fleisher LA, Guralnik JM, Fried LP. Physiological complexity underlying heart rate dynamics and frailty status in community-dwelling older women. J Am Geriatr Soc. 2008 Sep;56(9):1698-703.
    View on Pubmed

    Varadhan R, Seplaki C, Xue QL, Bandeen-Roche K, Fried LP.  Stimulus-response paradigm for characterizing the loss of resilience in homeostatic regulation associated with frailty.  Mechanisms of Ageing and Development; [Epub ahead of print]
    View on Pubmed

    Fried LP, Varadhan R, Bohr VA. Opinion section on frailty. Mech Ageing Dev. 2008 Nov;129(11):665. Epub 2008 Oct 4. 
    View on Pubmed

    Varadhan R, and Roland C (2008).  Simple and Globally Convergent Methods for Accelerating the Convergence of Any EM Algorithm S cand J Statist

    Varadhan R, Walston J, Cappola AR, Carlson MC, Wand GS, Fried LP (2008). Higher levels and blunted diurnal variation of cortisol in frail older women.J Gerontol A Biol Sci Med Sci.  Feb;63(2):190-5.

    Roland Ch., Varadhan R and Frangakis CE.  (2007). Squared polynomial extrapolation methods with cycling: an application to the positron emission tomography problem.   Numerical Algorithms.  Feb;44(2):159-172

    Roland Ch., and Varadhan R (2005), New iterative schemes for nonlinear fixed point problems with applications to problems with bifurcations and incomplete-data problems, Applied Numerical Mathematics, 55(2), 215-226.Y.

    Fujiwara Y, Chaves PHM, Takahashi R, Amano H, Kumagai S, Fujita K, Yoshida H, Wang DG, Varadhan R, Uchida H, Shinkai S (2004). Relationships between arterial pulse wave velocity and conventional Atherosclerotic risk factors in community-dwelling people. Preventive Medicine, 39, 1135-42.

    Li F, Frangakis CE, and Varadhan R (2004). Polydesigns in causal inference. Proceedings of the American Statistical Association, Section on Statistics in Epidemiology.
    View on Pubmed

    Varadhan R, and Frangakis, CE (2004), Revealing and addressing length bias and heterogeneous effects in frequency case-crossover studies, American Journal of Epidemiology, 159(6), 596-602.

    Frangakis CE and Varadhan R (2004), Systematizing the evaluation of partially controlled studies using principal stratification: from theory to practice, Statistica Sinica, 14, 945-947.

    Frangakis CE, Brookmeyer RS, Varadhan R, Mahboobeh S, Vlahov D, and Strathdee SA (2004). Methodology for evaluating a partially controlled longitudinal treatment using principal stratification, with application to a Needle Exchange Program, Journal of American Statistical Association, 98, 239-249.

    Frangakis CE and Varadhan R (2002), Confidence intervals for seasonal relative risk with null boundary values, Epidemiology, 13(6), 734-737.

    DiGiulio DC and Varadhan R (2000). Steady-state field-scale gas permeability estimation and pore-gas velocity calculation in a domain open to the atmosphere, Remediation, autumn issue.

    DiGiulio DC, Brusseau ML, and Varadhan Ravi (1999). Evaluation of mass flux to and from ground water using a vertical flux model (VFLUX): Application to the soil vacuum extraction closure problem, Ground Water Monitoring and Remediation, 21(1), 97-114.

    Varadhan Ravi, Chen JS, Wilson JT, Johnson JA, Gierke W, and Murdie L (1998). Evaluation of natural attenuation of benzene and dichloroethanes at the KL landfill, Bioremediation Journal, 2, 239-258.

    Johnson JA, Varadhan Ravi, and Rumery JK (1994). Estimation of solute concentrations using the path counting method, Ground Water, 32, 719-726.

    Jennings AA and Varadhan Ravi (1992). Interface penetration model formulation for analyzing wall-separation-influenced transient hydraulic conductivity data, Soil Science Society of America Journal, 56, 1023-1032.

    Varadhan Ravi and Jennings AA (1990). Penetration model parameter estimation from dynamic permeability measurements, Soil Science Society of America Journal, 54, 13-19.

    Jennings AA and Varadhan Ravi (1990). Analytic extensions of the discrete interface penetration model for dynamic permeability analysis, Soil Science Society of America Journal, 54, 7-12.

    Varadhan Ravi and Jennings AA (1990). Monte Carlo techniques applied to parameter estimation for permeability-altering soil/permeant interaction models, (In) Computer Techniques in Environmental Studies III, (ed.) Zannetti P, Springer-Verlag, NY.

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    Department/Division

    • Medicine - Geriatric Medicine

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