I know I'm always linking research articles to how the Brain functions but that's what I do! Anyway, the reason people who are bored die earlier is do to the brain not being stimulated enough. There are three things the neurons in the brain need to survive: Oxygen, Glucose, and activation aka stimulus. If any of the three are missing you will have cell death. You may be asking the question than why are these people dieing of heart attacks? Through neuroresearch scientists have found the left side of your brain controls the hearts rhythm and speed. The right side of the brain controls the speed only. If someone is having a left sided brain issue they can have Tachycardia(speeding up of the heart)and arrhythmia(heart beat is irregular). This is the worse case scenario. If the right side of brain is having difficulty firing you will only get tachycardia. When the brain is bored or under stimulated you have slow neuronal death. So stop reading my ramblings and go get some exercise!