But it was more than a simple lack of sleep.

I got to the Senate office building early, despite the lack of sleep.

"Perhaps it has something to do with your lack of sleep."

The lack of sleep was beginning to tell on him.

Maybe it was lack of sleep rather than age after all.

Remember that no one was ever killed by lack of sleep.

He knew in fact that it was more from lack of sleep than anything else.

I went to bed early that night to make up for the previous night's lack of sleep.

The lack of sleep seemed to catch up to her all at once.

It must have been the lack of sleep that finally got to him.