Thanks for your question.
There is no link between Sadistic personalities and people who have been diagnosed with Aspergers. People with Aspergers tend to have problems interacting with people and interpreting normal social cues. Someone who is sadistic would have characteristics of being very mean spirited, manipulative, and would treat people in a very degrading way. While it is certainly possible for someone to have Aspergers and be Sadistic, there is no link between the two that would indicate that a person affected with one of these problems would be more likely to have the other as well.
I hope I've been able to answer your question, and if there's anything else I can do to help please let me know.
What about a 4-5yr olds with aspergers who demonstrate aggressive behavior and typically can't keep from hurting other siblings but not other children?
Do you think this aggressive behavior merits further evaluation by a mental health expert? Furthermore, do you know if there is a correlation with this behavior and physically disciplining a child (spanking)?