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Ronald Gangnon

Professor of Biostatistics

University of Wisconsin-Madison

Biography

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.

Interests

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

Education

  • 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

Publications

Recent Changes in the Patterns of Breast Cancer as a Proportion of All Deaths by Race and Ethnicity

Background: Recent reports suggest that racial differences in breast cancer incidence rates have decreased. We examined whether these findings apply to breast cancer mortality while considering age, period, and cohort influences on both absolute and relative measures of breast cancer mortality. Methods: Using publicly available datasets (CDC Wonder, Human Mortality Database), we developed an age-period-cohort model of breast cancer mortality and breast cancer deaths as a proportion of all deaths during 1968-2019 among all women and by five race/ethnicity groups with sufficient numbers for estimation: Hispanic (all races), American Indian/Alaska Native and Asian/Pacific Islanders (regardless of ethnicity), non-Hispanic Black, and non-Hispanic White. Results: Initially increasing after 1968, age-adjusted breast cancer mortality rates have decreased among all racial/ethnic groups since 1988. The age-adjusted percent of all deaths due to breast cancer also has been declining for non-Hispanic White women since about 1990 while increasing or holding steady for other race/ethnic groups. In 2019, the age-adjusted percent of deaths due to breast cancer for women was highest for Asian/Pacific Islanders (5.6%) followed by non-Hispanic Black (4.5%), Hispanic (4.4%), non-Hispanic White (4.1%), and American Indian/Alaska Native women (2.6%). Conclusions: Breast cancer mortality disparities are now greater on both relative and absolute scales for non-Hispanic Black women, and using the relative scale for Asian/Pacific Islanders and Hispanic women, compared with non-Hispanic White women for the first time in 50 years.

Weapon-Carrying Among Boys in US Schools by Race/Ethnicity: 1993-2019

Background: High adolescent gun-related mortality, gun-violence, pro-gun policies, white supremacy, and the long-term socioeconomic and other effects of racial oppression are intricately linked in the United States. Racist prejudice depicts male individuals of color as more prone to criminality than White males. We described long-term patterns of weapon-carrying in US schools among Non-Hispanic White, Non-Hispanic Black/African American, and Hispanic boys, hypothesizing that in contrast to racist stereotypes, boys of color did not bring weapons into schools more often than Non-Hispanic White boys in recent years. Methods: We conducted a time series analysis using 1993-2019 Youth Risk Behavior Surveillance System data comparing boys’ self-reported weapon-carrying in a nationally representative sample of US high schools by race/ethnicity and age, and by self-reported experience of safety and violence at school. Results: Weapon-carrying in schools has declined among all boys. Comparing all schools, we found no significant differences in weapon-carrying (4-5%) by race/ethnicity in 2017/2019. Boys who reported experiencing violence or feeling unsafe at school were at least twice as likely to bring a weapon into school, and such negative experiences were more common among boys of color (8-12%) than Non-Hispanic White boys (4-5%). In schools perceived as safer, NonHispanic White boys have been more likely to bring weapons into schools than Non-Hispanic Black/African American or Hispanic boys in the past 20 years. Conclusion: Our findings contradict racist prejudice with regards to weapon-carrying in schools, particularly in more favorable school environments. Making school safer may reduce weaponcarrying in schools where weapon-carrying is most common.

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.