About

Dr. Sadie J. Ryan is a Professor of Medical Geography at the University of Florida, where she also serves as Principal Investigator at the Emerging Pathogens Institute and Co-Director of the Florida Climate Institute. Her interdisciplinary research focuses on the interface of medical geography and ecology, with particular emphasis on climate-health issues, modeling vector-borne diseases, geospatial models for intervention, and quantifying social-ecological risks of disease emergence and exposure in a changing world. Her work incorporates tools from medical geography, applied ecology, and social sciences, utilizing techniques across laboratory, field, and computational settings. Dr. Ryan's research aims to understand the implications of climate and ecological changes on disease transmission, conservation, and sustainability. She has contributed to numerous funded projects, including the NSF Center for Analysis and Prediction of Pandemic Expansion, the Wellcome Trust TACTIC, and the NSF VectorByte platform, among others. Her scholarly output includes publications on vector-borne diseases, climate impacts on health, and disease ecology. She holds a PhD in Environmental Science, Policy and Management from the University of California at Berkeley and a B.A. in Ecology and Evolutionary Biology from Princeton University.

Research topics

• Medicine
• Internal medicine
• Endocrinology
• Physical therapy
• Surgery

Selected publications

• Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes

  New England Journal of Medicine · 2023 · 2402 citations

  Senior authorCorresponding
  • Medicine
  • Internal medicine
  • Surgery

  BACKGROUND: Semaglutide, a glucagon-like peptide-1 receptor agonist, has been shown to reduce the risk of adverse cardiovascular events in patients with diabetes. Whether semaglutide can reduce cardiovascular risk associated with overweight and obesity in the absence of diabetes is unknown. METHODS: In a multicenter, double-blind, randomized, placebo-controlled, event-driven superiority trial, we enrolled patients 45 years of age or older who had preexisting cardiovascular disease and a body-mass index (the weight in kilograms divided by the square of the height in meters) of 27 or greater but no history of diabetes. Patients were randomly assigned in a 1:1 ratio to receive once-weekly subcutaneous semaglutide at a dose of 2.4 mg or placebo. The primary cardiovascular end point was a composite of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke in a time-to-first-event analysis. Safety was also assessed. RESULTS: A total of 17,604 patients were enrolled; 8803 were assigned to receive semaglutide and 8801 to receive placebo. The mean (±SD) duration of exposure to semaglutide or placebo was 34.2±13.7 months, and the mean duration of follow-up was 39.8±9.4 months. A primary cardiovascular end-point event occurred in 569 of the 8803 patients (6.5%) in the semaglutide group and in 701 of the 8801 patients (8.0%) in the placebo group (hazard ratio, 0.80; 95% confidence interval, 0.72 to 0.90; P<0.001). Adverse events leading to permanent discontinuation of the trial product occurred in 1461 patients (16.6%) in the semaglutide group and 718 patients (8.2%) in the placebo group (P<0.001). CONCLUSIONS: In patients with preexisting cardiovascular disease and overweight or obesity but without diabetes, weekly subcutaneous semaglutide at a dose of 2.4 mg was superior to placebo in reducing the incidence of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke at a mean follow-up of 39.8 months. (Funded by Novo Nordisk; SELECT ClinicalTrials.gov number, NCT03574597.).

  DOI

• Risk Factors for the Development of Retinopathy in Prediabetes and Type 2 Diabetes: The Diabetes Prevention Program Experience

  Diabetes Care · 2022 · 29 citations

  • Medicine
  • Internal medicine
  • Endocrinology

  OBJECTIVE: To determine glycemic and nonglycemic risk factors that contribute to the presence of diabetic retinopathy (DR) before and after the onset of type 2 diabetes (T2D). RESEARCH DESIGN AND METHODS: During the Diabetes Prevention Program (DPP) and DPP Outcome Study (DPPOS), we performed fundus photography over time in adults at high risk for developing T2D, including after they developed diabetes. Fundus photographs were graded using the Early Treatment Diabetic Retinopathy Study (ETDRS) grading system, with DR defined as typical lesions of DR (microaneurysms, exudates, hemorrhage, or worse) in either eye. RESULTS: By DPPOS year 16 (∼20 years after random assignment into DPP), 24% of 1,614 participants who had developed T2D and 14% of 885 who remained without diabetes had DR. In univariate analyses, using results from across the entire duration of follow-up, American Indian race was associated with less frequent DR compared with non-Hispanic White (NHW) race, and higher HbA1c, fasting and 2-h plasma glucose levels during an oral glucose tolerance test, weight, and history of hypertension, dyslipidemia, and smoking, but not treatment group assignment, were associated with more frequent DR. On multivariate analysis, American Indian race was associated with less DR compared with NHW (odds ratio [OR] 0.36, 95% CI 0.20-0.66), and average HbA1c was associated with more DR (OR 1.92, 95% CI 1.46-1.74 per SD [0.7%] increase in HbA1c). CONCLUSIONS: DR may occur in adults with prediabetes and early in the course of T2D. HbA1c was an important risk factor for the development of DR across the entire glycemic range from prediabetes to T2D.

  PublisherOA PDFDOI

• Effect of Metformin and Lifestyle Interventions on Mortality in the Diabetes Prevention Program and Diabetes Prevention Program Outcomes Study

  Diabetes Care · 2021 · 98 citations

  • Medicine
  • Internal medicine
  • Endocrinology

  OBJECTIVE: To determine whether metformin or lifestyle modification can lower rates of all-cause and cause-specific mortality in the Diabetes Prevention Program and Diabetes Prevention Program Outcomes Study. RESEARCH DESIGN AND METHODS: From 1996 to 1999, 3,234 adults at high risk for type 2 diabetes were randomized to an intensive lifestyle intervention, masked metformin, or placebo. Placebo and lifestyle interventions stopped in 2001, and a modified lifestyle program was offered to everyone, but unmasked study metformin continued in those originally randomized. Causes of deaths through 31 December 2018 were adjudicated by blinded reviews. All-cause and cause-specific mortality hazard ratios (HRs) were estimated from Cox proportional hazards regression models and Fine-Gray models, respectively. RESULTS: = 131). Compared with placebo, metformin did not influence mortality from all causes (HR 0.99 [95% CI 0.79, 1.25]), cancer (HR 1.04 [95% CI 0.72, 1.52]), or cardiovascular disease (HR 1.08 [95% CI 0.70, 1.66]). Similarly, lifestyle modification did not impact all-cause (HR 1.02 [95% CI 0.81, 1.28]), cancer (HR 1.07 [95% CI 0.74, 1.55]), or cardiovascular disease (HR 1.18 [95% CI 0.77, 1.81]) mortality. Analyses adjusted for diabetes status and duration, BMI, cumulative glycemic exposure, and cardiovascular risks yielded results similar to those for all-cause mortality. CONCLUSIONS: Cancer was the leading cause of mortality among adults at high risk for type 2 diabetes. Although metformin and lifestyle modification prevented diabetes, neither strategy reduced all-cause, cancer, or cardiovascular mortality rates.

  PublisherOA PDFDOI

• Serum urate and cardiovascular events in the DCCT/EDIC study

  Scientific Reports · 2021 · 7 citations

  • Medicine
  • Internal medicine

  In type 2 diabetes, hyperuricemia is associated with cardiovascular disease (CVD) and the metabolic syndrome (MetS), but associations in type 1 diabetes (T1D) have not been well-defined. This study examined the relationships between serum urate (SU) concentrations, clinical and biochemical factors, and subsequent cardiovascular events in a well-characterized cohort of adults with T1D. In 973 participants with T1D in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study (DCCT/EDIC), associations were defined between SU, measured once in blood collected 1997-2000, and (a) concurrent MetS and (b) incident 'any CVD' and major adverse cardiovascular events (MACE) through 2013. SU was higher in men than women [mean (SD): 4.47 (0.99) vs. 3.39 (0.97) mg/dl, respectively, p < 0.0001], and was associated with MetS features in both (men: p = 0.0016; women: p < 0.0001). During follow-up, 110 participants (11%) experienced "any CVD", and 53 (5%) a MACE. Analyzed by quartiles, SU was not associated with subsequent CVD or MACE. In women, SU as a continuous variable was associated with MACE (unadjusted HR: 1.52; 95% CI 1.07-2.16; p = 0.0211) even after adjustment for age and HbA1c (HR: 1.47; 95% CI 1.01-2.14; p = 0.0467). Predominantly normal range serum urate concentrations in T1D were higher in men than women and were associated with features of the MetS. In some analyses of women only, SU was associated with subsequent MACE. Routine measurement of SU to assess cardiovascular risk in T1D is not merited.Trial registration clinicaltrials.gov NCT00360815 and NCT00360893.

  DOI

• The Type and Amount of Dietary Fat Affect Plasma Factor VIIc, Fibrinogen, and PAI-1 in Healthy Individuals and Individuals at High Cardiovascular Disease Risk: 2 Randomized Controlled Trials

  Journal of Nutrition · 2020 · 9 citations

  • Internal medicine
  • Endocrinology
  • Medicine
  PublisherOA PDFDOI

• The Impact of Physical Activity on the Prevention of Type 2 Diabetes: Evidence and Lessons Learned From the Diabetes Prevention Program, a Long-Standing Clinical Trial Incorporating Subjective and Objective Activity Measures

  Diabetes Care · 2020 · 72 citations

  • Medicine
  • Internal medicine
  • Physical therapy

  OBJECTIVE: Across the Diabetes Prevention Program (DPP) follow-up, cumulative diabetes incidence remained lower in the lifestyle compared with the placebo and metformin randomized groups and could not be explained by weight. Collection of self-reported physical activity (PA) (yearly) with cross-sectional objective PA (in follow-up) allowed for examination of PA and its long-term impact on diabetes prevention. RESEARCH DESIGN AND METHODS: = 1,793). Mixed models determined PA differences across treatment groups. The association between PA and diabetes incidence was examined using Cox proportional hazards models. RESULTS: = 0.001 and 0.047). All associations remained significant with the addition of weight in the models. CONCLUSIONS: PA was inversely related to incident diabetes in the entire cohort across the study, with cross-sectional accelerometry results supporting these findings. This highlights the importance of PA within lifestyle intervention efforts designed to prevent diabetes and urges health care providers to consider both PA and weight when counseling high-risk patients.

  PublisherOA PDFDOI

Recent grants

• Core 02: Biostatistics, Epidemiology & Research Design Core

  NIH · $96.4M · 2012–2027

• NIH Grant R23CA039569

  NIH · $165k · 1988

Frequent coauthors

• Catherine M. Champagne

  173 shared

• George A. Bray

  160 shared

• Donald A. Williamson

  Pennington Biomedical Research Center

  130 shared

• Rena R. Wing

  Miriam Hospital

  101 shared

• David B. Allison

  98 shared

• James O. Hill

  University of Alabama at Birmingham

  90 shared

• Steven E. Kahn

  University of Washington

  90 shared

• Thomas A. Wadden

  87 shared

Labs

• GeographyPI

Education

• Postdoctoral Fellow, National Center for Ecological Analysis and Synthesis (NCEAS)

  University of California Santa Barbara

  2011

• Postdoctoral Fellow (NSF Bioinformatics), Anthropology

  Stanford University

  2008

• PhD, Environmental Science, Policy, and Management

  University of California Berkeley

  2006

• BA, Ecology and Evolutionary Biology

  Princeton University

  1998

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