An Incident in the Subway

Every weekday I go to work by subway.
One day after work, I was sitting on a seat in the subway as usual. There were one old lady on my opposite seat and a young woman next to me. I tried to read a book, but as soon as I opened the book, I got very sleepy. I began to nod over my reading; half conscious, half unconscious.

When the subway arrived at the station near my house, I awaked immediately and was stood up. Just then, one old lady sitting on my opposite seat came near to me, smiling.
She said, 'Oh, you must've been too tired!'
What? I was tired indeed, but... why she suddenly said such a thing?
The old lady went on her talking,
'What a patient woman she is, for you!'
I couldn't understand what she meant, but when I turned my face right, I found the young woman next to me looked very displeased.
Then I realized; I must have done something terrible!!
I said to them timidly,'Oh, I...I'm sorry.' Then they forgave me,
'No, no problem', and got off the subway without saying any more.

Even so, what on earth did I do? Was my body swaying? Did I leaned against the young woman? Or was I snoring loudly?

I wanted to know that very much, but I couldn't ask them because I was too embarassed. I'll never know the truth forever.
I decided to forget this awful incident, but I will never sleep in the subway.