Scientific backing for the concept of beauty sleep.? Being Attractive and Looking Healthy:

The study, led by John Axelsson from the Karolinska Institutet in Sweden, investigated the relationship between sleep and perceptions of attractiveness and health. The authors believe this research is important in today's 24 hour society with the number of people suffering from sleep disorders and disturbed sleep on the rise.

Twenty-three participants between the ages of 18 to 31 took part in the study. They were photographed between 2pm and 3pm on two occasions, once after normal sleep and once after being deprived of sleep. Smokers were excluded from the research and no alcohol was allowed for two days prior to the experiment

I have always thought this to be the case personally from what I have observed and from personal experience.
It may seem like an obvious conclusion but I still find it of interest that we have official research to back up the age old saying "Beauty Sleep"

www.sciencedaily.com

Journal Reference: 1. John Axelsson, Tina Sundelin, Michael Ingre, Eus J W Van Someren, Andreas Olsson, Mats Lekander. Beauty sleep: experimental study on the perceived health and attractiveness of sleep deprived people. BMJ, 341 DOI: 10.1136/bmj.c6614