Have any Marvel/DC superheroes died of natural causes?

Question

Reviewing an answer on another question, someone posited that Professor X is a mutant, and thus not subject to normal rules of mortality. This isn't really true, but it brought up an interesting idea, and after wracking my brain, I can't come up with a single example.

Within the Marvel or DC universes, has any superhero died of natural causes (old age, natural disease, etc)?

For purposes of this question, let's limit this to primary continuities/universes (The Watchmen was published by DC, but don't exist within the main DC universe). Being killed in a battle, or from injuries sustained in a battle would also not count.

Answer 1

There are several super-powered characters from both DC and Marvel on Wikipedia's List of deceased American comic book characters who died of mundane causes. (Credit to Sean Duggan for finding that list.)

DC Universe

• Amazing-Man died of cancer.
• Black Canary died of cancer. (This was after exposure to radiation during a battle, so it's not really a natural death. It was also retconned a few years later.)
• Enemy Ace died of natural causes.
• The Question died of lung cancer.

Marvel

• Captain Marvel (Mar-Vell) died of cancer from toxic nerve gases (so not really a natural death).
• Dennis Sykes died of cancer (as a direct result of the chemicals that gave him superpowers, but he had one month to live).
• Jeffrey Mace (the Patriot, and once Captain America) died of cancer.
• Trick Shot died of cancer.
• Two-Gun Kid died of natural causes.
• Union Jack (Brian Falsworth) died in an automobile accident.
• Union Jack (James Montgomery Falsworth) died of heart attack.
• Whizzer died of a heart attack (but this was during a battle, so not really a natural death).