Wikipedia describes Insomnia as:
Insomnia is a symptom of any of several sleep disorders, characterized by persistent difficulty falling asleep or staying asleep despite the opportunity. Insomnia is a symptom, not a stand-alone diagnosis or a disease. By definition, insomnia is "difficulty initiating or maintaining sleep, or both" and it may be due to inadequate quality or quantity of sleep. It is typically followed by functional impairment while awake. Both organic and non-organic insomnia without other cause constitute a sleep disorder, primary insomnia
However, I think it is they way all of the smart people get more hours out of the day.