Detectives are treating the "despicable" attack on 93-year-old Emma Winnall as murder after she died of the injuries sustained when beaten in her own bed earlier this month.
The grandmother suffered a fractured skull, broken arm and severed finger in the attack that led to her family releasing a picture of her injuries in the hope it would persuade people with information to come forward.
Superintendent Richard Baker from West Midlands Police said: "This is desperately sad news... our condolences go out to Emma's family and friends.
"Clearly, this has now become a murder inquiry. But given the extent of Emma's injuries, combined with her age and vulnerability, this investigation has always been treated with the same level of seriousness as a murder investigation."
The attack appalled people living nearby on the quiet residential estate in Moseley, Birmingham. There were no obvious signs of anyone forcing their way into the elderly lady's ground floor flat.
In the days that followed the beating Mrs Winnall's children appealed for information .
Her daughter Joyce Blencoe told a news conference: "It's broken my heart to hear my frail and defenceless mum in hospital manage to say she was screaming for help and no one came.
"To see your mum viciously beaten and covered in blood is the most horrific nightmare."
Mrs Winnall died in the early hours of Tuesday after spending a month in hospital. A post-mortem examination will now be carried out.
Supt Baker said: "We were able to speak to Mrs Winnall in hospital on two occasions in the days following her ordeal; the information she provided continues to form part of our investigation.
"No one capable of carrying out such a despicable attack deserves protecting - I'm asking people to look into their consciences and if they have any suspicions about who may be responsible to contact police."
A 56-year-old woman and a 28-year-old man from the Hall Green area were arrested in connection with the attack earlier this month but have since been released on police bail.