The study results document a sharp drop in heart disease in just 60 years. Researchers are not sure which factors played the largest role in this decline. Was it less smoking, lower cholesterol levels (from a healthier diet), or less hypertension (high blood pressure)? Some researchers believe most of the drop came from the fact that the military is now all-volunteer and that standards for recruits are much higher than they were when conscription was heavily used during the Korean and Vietnam Wars. Since many men avoided conscription, the army had to lower health standards to get the larger (than today) number of troops needed for the Cold War military.
Another factor was that many World War II veterans had joined the reserves and were called up for combat duty in Korea. These older men were more likely to have coronary heart disease simply because they were older and had already undergone lots of stress from World War II service. Then there was the different nature of the two wars. Korea was a conventional conflict, with the first year involving a lot of movement and heavy combat. The last two years were trench war with occasional heavy combat and constant stress from enemy sniping and mortar fire. Whatever the causes turn out to be, this study reinforces the belief that the current American armed forces are the healthiest and most professional the U.S. has ever had.