that the risk taker, party animal, heavy smoker, drinker etc etc etc personality type may have done himself in by some other means early enough in life to jump the gun on PD. Car accidents, boating accidents, employment in high risk jobs and other activities that adrenaline junkies indulge in would reduce their availability for the PD experience. Not to mention those who would have been murder victims (it's not the teetotalers who get murdered by jealous lovers). Just something to think about.