He had worked most of the night through and started the day on three hours' sleep.

You know I've always done just fine on four hours' sleep.

He'd been short on sleep last night, and his body knew it.

Now everything is under control I can catch up on my sleep.

He would certainly be able to catch up on his sleep.

About her only choice was to go to bed and catch up on much needed sleep.

She is even able to use some of the time to catch up on sleep.

The truth was I wanted to fall on a soft bed and sleep.

You'd better take a week off and catch up on sleep.

Soon enough we'll have to go back on board ship and sleep.