Are you familiar with the concept of 'signal to noise ratio'? In a quiet room you can hear a whisper but you cannot hear a scream in a very noisy room.
The healthy have very low noise so you'll notice an extra 10/100,000 of the group having heart attacks since the number is normally <1/100,000. If the unhealth are normally at 1,000/100,000 then you won't notice an extra 10/100,000. All of these numbers are made up just to explain the idea.
Are you familiar with the concept of 'signal to noise ratio'? In a quiet room you can hear a whisper but you cannot hear a scream in a very noisy room.
The healthy have very low noise so you'll notice an extra 10/100,000 of the group having heart attacks since the number is normally <1/100,000. If the unhealth are normally at 1,000/100,000 then you won't notice an extra 10/100,000. All of these numbers are made up just to explain the idea.