Ramzi W. Nahhas, Ph.D.

Associate Professor

(937) 775-1421 (voice)
(937) 775-1456 (fax)

E-mail: ramzi.nahhas@wright.edu


Major Active Projects

Dr. Nahhas is highly active in collaborative projects, utilizing modern statistical methods to analyze data from a wide range of biomedical research areas. These disciplines include craniofacial growth and development, skeletal and dental maturation, somatic growth and development, obesity, cardiometabolic risk across the lifespan, illicit drug use, and psychiatric disorders. This diversity stems from the applicability of his focal statistical expertise to a wide variety of biomedical questions. Dr. Nahhas’ specific methodological areas of expertise include longitudinal data analysis, in particular linear and non-linear mixed models, growth curve modeling, and the analysis of missing data.

  • Longitudinal modeling of craniofacial growth trajectories
  • Prediction of craniofacial growth (amount and timing)
  • Estimation of maturity (skeletal maturity based on the bones of the hand and wrist; dental maturity)
  • Adiposity, Disease Risk Factors, and Lifetime Health
  • Opioid Use Trajectories and HIV Risk Among Young Adults in Ohio

Resources

Education

The Ohio State University, Columbus, Ph.D., 1999, Biostatistics

The Ohio State University, Columbus, M.S., 1995, Statistics

The Ohio State University, Columbus, B.S., 1993, Mathematics

Professional Positions

2014–present: Associate Professor, Lifespan Health Research Center, Department of Community Health, Boonshoft School of Medicine, Wright State University, Dayton, OH

2009–2014: Assistant Professor, Lifespan Health Research Center, Department of Community Health, Boonshoft School of Medicine, Wright State University, Dayton, OH

2008–2009: Research Assistant Professor, Lifespan Health Research Center, Department of Community Health, Boonshoft School of Medicine, Wright State University, Dayton, OH

2007–2008: Sr. Biostatistician, Lifespan Health Research Center, Department of Community Health, Boonshoft School of Medicine, Wright State University, Dayton, OH

2006–2007: Language Survey Coordinator, Department of Linguistics, Payap University and SIL International, Chiang Mai, Thailand

2004–2006: Language Survey Specialist, Department of Linguistics, Payap University and SIL International, Chiang Mai, Thailand

2002: Statistics Instructor, Graduate Institute of Applied Linguistics, Dallas, TX

2000–2007: Language Surveyor, Wycliffe Bible Translators, Dallas, TX and Chiang Mai, Thailand (seconded to SIL International 2003-2007)

1999–2000: Research Scientist, Battelle, Columbus, OH

Select Publications

Nahhas RW, Valiathan M, Sherwood RJ. Variation in onset, duration, intensity, and direction of adolescent growth in the mandible, maxilla, and cranial base: the Fels Longitudinal Study.
The Anatomical Record, 2014, 297(7):1195–1207.
DOI 10.1002/ar.22918. PMID 24737730. (link)

Carlson RG, Nahhas RW, Daniulaityte R, Martins SS, Li L, Falck RS. Latent class analysis of non-opioid dependent illegal pharmaceutical opioid users in Ohio.
Drug and Alcohol Dependence, 2014, 134:259-266.
DOI: 10.1016/j.drugalcdep.2013.10.004. PII: S0376-8716(13)00415-8. PMID 24210772. PMCID PMC3865109. (link)

Nahhas RW, Sherwood RJ, Chumlea WC, Duren DL. An update of the statistical methods underlying the FELS method of skeletal maturity assessment.
Annals of Human Biology, 2013, 40(6):505-514.
DOI: 10.3109/03014460.2013.806591. PMID 23992229. PMCID PMC4013782. (link)

von Hippel PT, Nahhas RW. Extending the history of child obesity in the United States: The Fels Longitudinal Study, birth years 1930 to 1993.
Obesity, 2013, 21(10):2153-2156.
DOI 10.1002/oby.20395. PMID 23512972. PMCID PMC3695078. (link)

Nahhas RW, Sherwood RJ, Chumlea WC, Towne B, Duren DL. Predicting the timing of maturational spurts in skeletal age.
American Journal of Physical Anthropology, 2013, 150:68-75.
DOI 10.1002/ajpa.22142. PMID 23283666. PMCID PMC3988703. (link)

Duren DL, Šešelj M, Froehle AW, Nahhas RW, Sherwood RJ. Skeletal growth and the changing genetic landscape during childhood and adulthood.
American Journal of Physical Anthropology, 2013, 150:48-57.
DOI 10.1002/ajpa.22183. PMID 23283664. PMCID PMC3539213. (link)

Froehle AW, Nahhas RW, Sherwood RJ, Duren DL. Age-related changes in spatiotemporal characteristics of gait accompany ongoing lower limb linear growth in late childhood and early adolescence.
Gait and Posture, 2013, 38(1):14-19.
DOI 10.1016/j.gaitpost.2012.10.005. PMID 23159678. PMCID PMC3580126. (link)

Linabery AM, Nahhas RW, Johnson W, Choh AC, Towne B, Odegaard AO, Czerwinski SA, Demerath EW. Stronger influence of maternal than paternal obesity on infant and early childhood body mass index: the Fels Longitudinal Study.
Pediatric Obesity, 2013, 8(3):159-169.
DOI 10.1111/j.2047-6310.2012.00100.x. PMID 23042783. PMCID PMC3765070. (link)

Šešelj M, Nahhas RW, Sherwood RJ, Chumlea WC, Towne B, Duren DL. The influence of age at menarche on cross-sectional geometry of bone in young adulthood.
Bone, 2012, 51(1):38-45.
DOI 10.1016/j.bone.2012.03.030. PMID 22513271. PMCID PMC3584571. (link)

Falck RS, Nahhas, RW, Li, L, Carlson RG. Surveying teens in school to assess the prevalence of problematic drug use.
Journal of School Health, 2012, 82(5):217-224.
DOI 10.1111/j.1746-1561.2012.00690.x. PMID 22494092. (link)

Choh AC, Nahhas RW, Lee M, Choi YS, Chumlea WC, Duren DL, Sherwood RJ, Towne B, Siervogel RM, Demerath EW, Czerwinski SA. Secular trends in blood pressure during early to middle adulthood: The Fels Longitudinal Study.
Journal of Hypertension, 2011, 29(5):838-845.
DOI 10.1097/HJH.0b013e328344da30. PMID 21430562. PMCID PMC3988666. (link)

Lee M, Nahhas RW, Choh AC, Demerath EW, Duren DL, Chumlea WC, Sherwood RJ, Towne B, Siervogel RM, Czerwinski SA. Longitudinal changes in calcaneal quantitative ultrasound measures during childhood.
Osteoporosis International, 2011, 22(8):2295-2305.
DOI 10.1007/s00198-010-1458-0. PMID 20976593. PMCID PMC3988661. (link)

Nahhas RW, Choh AC, Lee M, Chumlea WC, Duren DL, Siervogel RM, Sherwood RJ, Towne B, Czerwinski SA. Bayesian longitudinal plateau model of adult grip strength.
American Journal of Human Biology, 2010, 22(5):648–656.
DOI 10.1002/ajhb.21057. PMID 20737612. PMCID PMC3988672. (link)

Nahhas RW, Wolfe DA, Chen H. Ranked set sampling: ranking error models and estimation of visual judgment error variance.
Biometrical Journal, 2004, 46(2):255-263.
DOI 10.1002/bimj.200210021. (link)

Nahhas RW, Wolfe DA, Chen H. Ranked set sampling: cost and optimal set size.
Biometrics, 2002, 58(4):946-971. PMID 12495151. (link)

Ilich-Ernst JZ, McKenna AA, Badenhop NE, Clairmont AC, Andon MB, Nahhas RW, Goel P, Matkovic V. Iron status, menarche, and calcium supplementation in adolescent girls.
American Journal of Clinical Nutrition, 1998, 68(4):880-887.
PMID 9771866. [Erratum in: American Journal of Clinical Nutrition, 1999, 69(3):577]. (link)

Matkovic V, Ilich JZ, Skugor M, Badenhop NE, Goel P, Clairmont A, Klisovic D, Nahhas RW, Landoll JD. Leptin is inversely related to age at menarche in human females.
Journal of Clinical Endocrinology and Metabolism, 1997, 82(10):3239-3245.
PMID 9329346. (link)