Hyper-acceleration
Hyper-acceleration was a process whereby an individual experienced time at a faster rate than others. The Scalosians were hyper-accelerated due to radiation on their planet Scalos. 

What seemed like a few minutes to an accelerated individual went by much more quickly to an individual experiencing time conventionally. In fact, a person in normal time could not see a hyper-accelerated individual because he or she moved too fast. An individual in normal time heard a sound like a buzzing insect when in the presence of a hyper-accelerated person, which was really the sound of their speech, sped up to a very high rate.

When making the transition from normal time to accelerated, an individual's life span was shortened. In addition, they were susceptible to ular damage, which could result in the person aging to death in mere minutes as a result of the slightest injury. ()
Time
Medical conditions