Just to clarify as several have asked:
The CAA isnt there to keep pilots healthy or to treat them. It exists to minimise the risk of harm to the public, primarily from incapacitation. Thus whether a particular pathology will cost you your medical depends on the risk of incapacitation. The biggest risk in pilots with no known or identified issues is cardiovascular - a heart attack or a stroke. The CAA set down its own level of acceptability, accepting the risk is never zero as others have pointed out.
The risk of a 70 year old healthy pilot having a heart attack or stroke today is the same as the risk for a 50 year old colleague in the 1970s (dont quote me on exact ages and dates!!!). So if it was acceptable for the 50 year old to fly in 1970, it is acceptable for the 70 year old to fly today on a purely actuarial and scientific basis. Otherwise you are moving the goal posts.
I am always amazed, when this comes up, how many posters defend or support the status quo. I know Pprune isnt representative, but I can think of no other profession where turkeys vote for Christmas like this. Average life expectancy at 60 is possibly over 30 years and if you have flown all your working life and dont want to vegetate it is not that easy to see how such individuals will easily assimilate into society.