I'm pretty sure the higher your elevation, the smaller your average distance from the Sun. Furthermore, as distance from the center of the Earth increases, atmospheric density decreases and exposure to ionizing radiation like cosmic rays and gamma rays also increases. Keeping in mind both these factors, and utilizing Quigon's Three-Body Pablum, I posit that you will die faster, albeit infinitesimally, from radiation in the wake of a nuclear blast in Denver that you would somewhere less heightful.