Hello,
Thank you for writing to HCM about your query,
Brief Answer -
cause of sleepiness isn't easy to figure out, there are many reasons.
Explained Answer -
As you described your mother's age i would suggest you that knot to disturb her,
Because as her age is 91, She would need more rest than normal people.
Still i would like to inform you following causes for excessive sleep.
Not getting enough sleep -- sometimes by choice -- is the most common cause of excessive sleepiness.
Working at night and sleeping during the day is another.
Other causes include drug, alcohol, or cigarette use, lack of physical activity, obesity, and the use of certain medications.
But nodding off when you want or need to be awake may also be caused by an underlying condition.
Depression or a
sleep disorder -- such as
restless legs syndrome,
sleep apnea, or
narcolepsy -- are common causes of problem sleepiness.
Hope You will find it out helpful, and Take care of her.
Thanks And Regards,
Dr. Gaurav Prajapati