Police said the victim got into an altercation with two men in Michael's Corner Shop in the Hailesland Grove area of Edinburgh on Friday afternoon.
He managed to return home immediately after the incident, but later attended the city's Royal Infirmary.
He was subsequently transferred to the Western General Hospital where he is being treated for serious injuries to his head and face.
Detective Sergeant Neil Spowart said: "The victim has sustained a number of serious and painful injuries and we are trying to establish the exact circumstances surrounding this incident.
"Anyone who was in the Hailesland Grove area on Friday afternoon and witnessed the attack or saw anything suspicious is asked to contact police immediately."
Police in Edinburgh are also appealing for witnesses after an assault and robbery between 11.30pm on Friday and 1.30am on Saturday in Leith Walk.
A 61-year-old man was walking past the Central Bar when a man and woman stopped and engaged him in conversation.
The man then ordered him to hand over his possessions and, after a struggle, the victim sustained fractures to his wrist and ribs. The suspects made off with his wallet and watch.
The male attacker is described as white, balding and wearing a dark blue jacket, blue jeans and dark footwear. The female is described as white with dark hair in a ponytail. She was wearing a blue-sleeved hooded top with grey hood, a purple body warmer and blue footwear.