Stuart Taylor, who had been claiming to be a worker offering to carry out small manual labour jobs, knocked on the door of the 91-year-old in Mariners Cottages, South Shields, asking for a glass of water on November 14, last year.
Newcastle Crown Court heard that after the victim came to the door, Taylor entered the house before he was eventually stopped by family members.
Taylor, 52, of Beach Road, South Shields, denied the offence of attempted dwelling house burglary but was found guilty by a jury after a trial.
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Jailing him for four years, Judge Timothy Gittins told Taylor, who appeared via link from custody: "You have an appalling record as an adult for offences of dishonesty and also of domestic burglary.
"You have received substantial sentences of imprisonment in the past and you have not learned your lesson.
"Here it was, a 91-year-old lady and a dementia sufferer, who nevertheless at the time was able to live by herself with the assistance of carers and regular visits off her family.
"You were found in the hallway and no doubt intent on taking what you could find had you not been disturbed.”
The court heard that the actions of Taylor, who has 72 previous convictions on his record, have since contributed to the victim no longer being able to live independently and she now resides in a care home.
The judge added: "In addition, you undoubtedly caused confusion for her son and daughter-in-law faced by you coming out of the premises.
"I'm quite satisfied you targeted your vulnerable victim.
"It's right to say other methods have been tried with you – community orders and suspended sentences – you have not learned from them."That said, I do take into account that nothing was actually taken with no suggestion of any threats or the like towards the victim."Jamie Adams, mitigating, said: "This is a very serious matter and I have to accept that."One can only hope he finds a way of making up to his family and few friends he does have to realise some life for himself."