An 85-year-old woman with dementia suffered head and facial injuries after a man broke into her home in Dumbarton.
The “despicable” attack took place at the house in Hawthornhill Road between 01:45 and 02:45.
The woman was taken to the Royal Alexandra Hospital for treatment.
The suspect, described as being about 6ft tall, of slim build and wearing dark clothing, made off on foot towards Castlehill Road. It is not known if anything was stolen.
Det Con Iain Allison, of Clydebank police office, said: “To break in and cause injuries to one of the most vulnerable members of our community in the middle of the night is an absolutely despicable act.
“The woman’s physical injuries will heal but this terrifying experience will no doubt stay with her.
“We will be doing everything in our power to find the person responsible. We are currently looking for any CCTV in the area and are making door-to-door inquiries.
“We would ask anyone who may have any information to get in touch with us.”
He added: “Officers will be carrying out extra patrols in the area and if you have any concerns you are encouraged to speak to them.