Jeffrey Ash killed his 83-year-old-mum Ellen before torching the family home in Colston, Glasgow, leaving the OAP's corpse inside.
A judge heard yesterday how the widow's condition had worsened and that Ash was "driven to the edge".
It emerged Mrs Ash was released from hospital just a week before she died - despite her son admitting he was having "difficulty" coping with her care.
The 50-year-old fled to London after the death and handed himself into police where he confessed: "I killed my mum last night. I could not see her suffering any more."
Ash admitted to charges of culpable homicide and wilful fire-raising in a case his QC described as "desperately sad".
The first-offender - who is remanded in custody - will be sentenced on September 19 at the High Court in Edinburgh.
The High Court in Glasgow heard Ash was the primary carer for his mum at the detached home they shared in the city's Everard Drive, Colston.
Mrs Ash suffered from dementia and her condition had deteriorated in the two years before she died.
It eventually reached the stage where Ash could apparently take no more.
The killing came to light when a member of the public noticed smoke bellowing from the family home in the early hours of March 21.
A 999 call was made before fire crews arrived and found Mrs Ash's badly burned corpse on the living room floor.
Ash's QC Donald Findlay said the killing was "desperately sad".
He said: "Jeffrey Ash was a loving son, who lost his mother some years ago and was left to tend and care someone he hardly knew."
Judge Lord Pentland remanded Ash in custody.