Ronald Gangnon

Professor of Biostatistics

University of Wisconsin-Madison


I am a Professor in the Department of Biostatistics and Medical Informatics and the Department of Population Health Sciences in the School of Medicine and Public Health at the University of Wisconsin-Madison. I have an affiliate appointment in the Department of Statistics.

I grew up in Duluth, Minnesota. I graduated from East High School in 1988. I received a BA in Mathematics and Economics in 1992 from the University of Minnesota-Duluth and an MS in Statistics in 1994 and a PhD in Statistics with emphasis in Biostatistics in 1998 from the University of Wisconsin-Madison. My PhD advisor was Murray Clayton.

I was a research scientist in the Statistical Data Analysis Center(SDAC) in the Department of Biostatistics and Medical Informatics at the University of Wisconsin-Madison, 1998-2005. I joined the faculty with a joint appointment in the Department of Biostatistics and Medical Informatics and the Department of Population Health Sciences in 2005.

I am an applied biostatistician focusing on problems in clinical and epidemiologic research. Current methodologic areas of interest include (1) multi-state models for incidence, progression and regression of ocular (and other) diseases, (2) small area estimation problems, particularly ranking, (3) spatial and spatio-temporal modeling, particularly cluster detection and high-dimensional variable selection and (4) age-period-cohort modeling.


  • Spatial and Spatio-Temporal Modeling
  • Age-Period-Cohort Models
  • Ranking
  • Multi-State Models


  • PhD in Statistics (emphasis in Biostatistics), 1998

    University of Wisconsin-Madison

  • MS in Statistics, 1994

    University of Wisconsin-Madison

  • BA in Mathematics and Economics, 1992

    University of Minnesota-Duluth


Provision of Immediate Long-Acting Reversible Contraceptives Before and After Wisconsin Medicaid’s Payment Change.

Objectives: To estimate the association between Medicaid unbundling of payment for long-acting reversible contraceptives (LARC) from the global delivery fee and immediate postpartum (IPP) LARC provision, in a state outside a select group of early-adopters. Results will also shed light on the potential moderating roles of hospital academic affiliation and Catholic status on the association between unbundling and IPP LARC provision. Methods: We used a pre-post design to examine the association between unbundling and IPP LARC provision. We observed Medicaid-covered childbirth deliveries in Wisconsin hospitals between January 2016-December 2017 (n=45,200) in the State Inpatient Database from the Agency for Healthcare Research and Quality’s Healthcare Cost and Utilization Project. We conducted multivariate regressions using generalized linear mixed models. Results: From 2016 to 2017, IPP LARC provision increased from 0.28% to 0.44% of deliveries (p=.003). In our adjusted model, IPP LARC provision was 1.55 times more likely in the post-period vs. the pre-period (95% CI: 1.12-2.13). Both before and after unbundling, IPP LARC provision was significantly more common in academic vs nonacademic settings and was exceedingly rare in Catholic institutions. Conclusions: In contrast to many early-adopting states, in this later-adopting state, Wisconsin Medicaid’s unbundling of LARC from the global fee did not meaningfully change rates of IPP LARC provision in the state. Results indicate that delivery hospital characteristics are strong correlates of access to IPP LARC and suggest the need for interventions—perhaps outside of the inpatient setting—to ensure that patients can access desired contraceptive methods promptly postpartum.

Clustered Spatio-Temporal Varying Coefficient Regression Model

In regression analysis for spatio-temporal data, identifying clusters of spatial units over time in a regression coefficient could provide insight into the unique relationship between a response and covariates in certain subdomains of space and time windows relative to the background in other parts of the spatial domain and the time period of interest. In this article, we propose a varying coefficient regression method for spatial data repeatedly sampled over time, with heterogeneity in regression coefficients across both space and over time. In particular, we extend a varying coefficient regression model for spatial-only data to spatio-temporal data with flexible temporal patterns. We consider the detection of a potential cylindrical cluster of regression coefficients based on testing whether the regression coefficient is the same or not over the entire spatial domain for each time point. For multiple clusters, we develop a sequential identification approach. We assess the power and identification of known clusters via a simulation study. Our proposed methodology is illustrated by the analysis of a cancer mortality dataset in the Southeast of the U.S.

Feasibility and Acceptability of Home-Based Strength Training in Endometrial Cancer Survivors

Purpose Physical activity is important for healthy cancer survivorship, yet many endometrial cancer survivors do not participate in recommended muscle-strengthening activity. The purpose of this study was to determine the feasibility of home-based muscle strengthening activity in endometrial cancer survivors. Methods Forty post-treatment endometrial cancer survivors were enrolled in a randomized trial, of twice-weekly home-based strength exercise versus wait-list control. The intervention included educational materials, exercise equipment (dumbbells, resistance bands), and support/feedback via video coaching sessions. Participants completed the exercises twice per week for 10 weeks, with a 5-week follow-up period. Feasibility was measured by program adherence, as well as safety of and satisfaction with the study. Results On average, participants were 60.9 years old (SD = 8.7), had a BMI of 39.9 kg/m2 (SD = 15.2), and were 2.9 years (SD = 1.2) since diagnosis. The majority (83%) had stage I disease at diagnosis. Seventy-five percent adhered to the exercise prescription of twice/week, with 85% of participants missing fewer than 3 of the workouts. Forty percent of participants continued workouts during the 5-week follow-up. Participants were highly satisfied with intervention. No injuries or adverse everts occurred. Conclusion This home-based program was feasible in endometrial cancer survivors. While adherence was measured, future research should focus on long-term maintenance of exercise and should explore progressions and modifications of exercises at a distance for various abilities. Implications for Cancer Survivors Muscle strengthening activities are recommended for all cancer survivors. This study shows that a home-based muscle strengthening exercise is feasible in endometrial cancer survivors.

Association of Macular Thickness with Age and Age-Related Macular Degeneration in the Carotenoids in Age-Related Eye Disease Study 2 (CAREDS2), An Ancillary Study of the Women’s Health Initiative

Purpose: To evaluate the relationship of retinal layer thickness with age and age-related macular degeneration (AMD) in the Carotenoids in Age-Related Eye Disease Study 2. Methods: Total retinal thickness within the macular area, and individual layer thickness was determined for CAREDS2 participants (n=906 eyes, 473 women) from the Women’s Health Initiative using Heidelberg spectral-domain optical coherence tomography (SD-OCT). Mean measurements within the OCT grid were compared across age tertiles (69-78, 78-83, 83-101 years) and AMD outcomes (no AMD, early, intermediate , late AMD). Results: Total retinal thickness in the central circle, inner ring, and outer ring were mean ± standard deviation 277 ± 34 μm, 326 ± 20 μm, and 282 ± 15 μm, respectively. Thickness did not vary by age in the central circle, but decreased with age in the inner and outer circles (p≤0.004). Specifically, ganglion cell (GCL), inner plexiform (IPL), and outer nuclear (ONL) layer thickness decreased with age in the inner and outer rings (p≤0.003). Age-adjusted retinal thickness in all three circles did not vary by AMD outcomes, except that the retinal pigment epithelium (RPE) layer thickness was greatest in eyes with late AMD (p≤0.001). After controlling for age, higher retinal ONL and lower RPE thickness were associated with better best corrected visual acuity. Conclusions: In this cohort of older women, a decrease in peripheral macular thickness was associated with increasing age, particularly in the GCL, IPL, and ONL. The GCL, PRL, and RPE layer contributed to variability in thickness in eyes with AMD. Among all retinal layers, ONL and RPE thickness were associated with visual acuity.

Enhanced Neutralizing Antibody Responses to Rhinovirus C and Age-Dependent Patterns of Infection

Rationale: Rhinovirus C (RV-C) can cause asymptomatic infection and respiratory illnesses ranging from the common cold to severe wheezing. Objectives: To identify how age and other individual-level factors are associated with susceptibility to RV-C illnesses. Methods: Longitudinal data from the Childhood Origins of ASThma (COAST) birth cohort study were analyzed to determine relationships between age and RV-C infections. Neutralizing antibodies specific for rhinovirus A (RV-A) and RV-C (3 types each) were determined using a novel polymerase chain reaction-based assay. We pooled data from 14 study cohorts in the United States, Finland, and Australia and used mixed-effects logistic regression to identify factors related to the proportion of RV-C versus RV-A detection. Measurements and Main Results: In COAST, RV-A and RV-C infections were similarly common in infancy, while RV-C was detected much less often than RV-A during both respiratory illnesses and scheduled surveillance visits (p<0.001, chi-square) in older children. The prevalence of neutralizing antibodies to RV-A or RV-C types was low (5%-27%) at age 2 years, but by age 16, RV-C seropositivity was more prevalent (78% vs. 18% for RV-A, p<0.0001). In the pooled analysis, the RV-C to RV-A detection ratio during illnesses was significantly related to age (p<0.0001), CDHR3 genotype (p<0.05), and wheezing illnesses (p<0.05). Furthermore, certain RV types (e.g., C2, C11, A78, A12) were consistently more virulent and prevalent over time. Discussion: Knowledge of prevalent RV types, antibody responses, and populations at risk based on age and genetics may guide the development of vaccines or other novel therapies against this important respiratory pathogen.