Background: Hospital-acquired pressure ulcers (HAPUs) are largely preventable yet still common occurrences in hospitals. The purpose of the current study is to determine how data from the electronic medical record can be used to better understand and predict HAPU formation over the course of a hospital admission. Methods: A case-control study on HAPUs was performed over an 8-month period at Yale New Haven Hospital. A Cox regression analysis model analyzed the impact of multiple factors on HAPU development including friction and shear, among other Braden score components. A receiver operating characteristic curve was calculated to determine the sensitivity and specificity of changes in these factors in predicting HAPU development. Results: On a sample of 8,790 admissions, HAPU incidence was 4.2% over the study period (6.3% per annum). The average hospital day for HAPU development was day 15.6 (± 19.3). The Cox regression analysis demonstrated that the volatility of the friction and shear component of Braden scores had a risk ratio of 28.6 (P < 0.01; CI, 14.5-56.4). Volatility in the friction and shear component was the most predictive factor with a high receiver operating characteristic curve area of 0.865 (CI, 0.847-0.882). Conclusions: Volatility of the friction and shear component of Braden scores appears to be the most significant factor preceding HAPU development at Yale New Haven Hospital. Efforts to place more focus on identifying and reducing volatility of this factor may help decrease HAPU risk for future patients.