UC Santa Barbara

Hypertension is a cause for concern for patients and doctors alike. Patients with highblood pressure have a greater risk of developing other serious health problems. There is evidence to suggest that UV radiation is negatively associated with blood pressure. However, it is unclear whether this negative relationship holds for the entire spectrum or sub-interval. An action spectrum describes the relationship over the entire spectrum. The purpose of this project is to investigate the action spectrum of UV on blood pressure to see if there is a range of wavelengths that is associated with a decrease in blood pressure. To determine this relationship, a functional linear mixed effects model is applied to a large dialysis patient dataset. In order to fit the desired model to a large dataset, new computational methods are developed. First, approximations are done using eigensystem truncation or the Nystrom method. Next, connections between mixed effects models and cubic splines are used to fit smoothing splines using lme. Finally, the lme.formula function in the nlme package is modified in order to fit the desired model. The results of the model imply that wavelengths between 297 and 320 nm are associated with decreases in blood pressure.