Yes definitely. Since stuttering is due to tension in the body and you generally feel more tense when tired, you will stutter more. You feel more tense when tired because your brain/body isn't working at full capacity meaning some parts of your functions will be overused to compensate for others. You will anticipate and stress more to compensate for lack of awareness etc. Your mind trying to protect you. But also in muscular tension as well. Sleep and diet play a role forsure