Living without sleep for eight days seems impossible, but it has been accomplished by a few individuals in the past. This extraordinary feat can be attributed to a rare genetic condition known as Fatal Familial Insomnia (FFI). A trick answer can be saying the person can sleep at night.
However, it is important to learn about what the effects might be on a serious note. FFI is a genetic disorder that affects the thalamus, the part of the brain responsible for regulating sleep.