I learned about my friends’ sleep problems by accident. We were having a cookout with three families not long ago, and the children were off playing by themselves. The couples sat down for an adult conversation that might otherwise have turned to Hollywood, parenting or Donald Trump, when suddenly one of the women announced she had a confession: She never got to see her husband.

She said she collapsed into bed soon after the children went to sleep, then woke up wired at 4:30 a.m., anxious about work deadlines. He came home late from his job, played with the children for a time, then went to bed after 11 p.m.

Instead of finding this situation unusual, every other person at the table had a similar story. One spouse liked to meditate in the morning, another liked to binge-watch television at night; one liked reading when the house quieted down after midnight, another liked making coffee before the house got chaotic at dawn.

One thing they all had in common is that they had radically incompatible sleep schedules with their spouses. Another is that they weren’t sure whether this was good or bad for their relationship.