article_snippet.sent: According to Professor David Hillman, those misplaced hours of sleep must be paid back in order to be functional for the entire week.
article_snippet.sent: A lot of us pay back a bit of that debt on the weekend
article_snippet.sent: Therefore, the hours must be paid back to avoid an error rate in alertness tasks.
highlights_snippet.sent: Professor David Hillman said it's important to pay back our sleep debts .
  