William Spencer died Saturday at University Hospitals in Iowa City after he was injured in the fire Friday night, officials said.
Osage Fire Chief Kurt Angell said the fire apparently started in the television room of the house ``near where he liked to sit, but we don't know how it started.''
Angell said the fire was extremely hot and caused extensive heat damage on the first floor of the home and smoke damage on the second floor.
Osage police officer Brian Wright tried to open the front door but couldn't because of the intense heat and smoke. He then went to a back door, saw Spencer's feet through the thick smoke and pulled him outside.
Spencer, a retired surgeon, had lived in Osage, just northeast of Mason City, since 1957.
The fire is under investigation by the state fire marshal's office.