The newspaper said Ditka was playing cards at a country club in suburban Chicago when the symptoms began.
Ditka, 73, suffered a heart attack in 1988, but no health problems had been reported in recent years. He is currently an NFL analyst for ESPN.
Ditka is one of only two men to have won a Super Bowl as a player, assistant coach and head coach.
He was a member of the Dallas Cowboys when they won Super Bowl VI, was part of the staff of Coach Tom Landry in Dallas when the Cowboys captured another Super Bowl six years later and coached the Bears to the NFL title following the 1985 season.
Ditka also coached the New Orleans Saints for three seasons. He joined the Pro Football Hall of Fame in 1988 as the first tight end to be inducted. He caught 427 passes during his career for 5,812 yards and 43 touchdowns.