Survivor Singer Jimi Jamison -- Death Due To Meth

The lead singer of Survivor died from a stroke and methamphetamine abuse ... according to autopsy results.

Jimi Jamison had a narrowing of his arteries and cardiovascular disease ... according to the report -- however it lists the brain stroke as the ultimate cause of death. He died back in September at his home in Memphis.

Jamison took over as the band's frontman in 1984 -- after their biggest hit, "Eye of the Tiger" -- but was responsible for several other hits like ... "The Search is Over" and "Is This Love?"

Jamison was 63.