The following information may be of interest to those old farts among us who spent some of their formative years in Vietnam during the war.
From July 1969 to June 1971 I spent most of the time living in platoon and company patrol bases in the Cambodian border area. It was not unusual for us to be sprayed by low-flying aircraft that, I believed at the time, were performing (ineffectual) mosquito control. I never heard of agent orange while in Vietnam. Shortly after leaving Vietnam and resuming a structured military physical conditioning routine, I realized that my physical abilities had been greatly reduced. Regardless of how hard I pushed myself in my daily fitness routine, I could never regain my pre-war studliness. I would be fatigued even after a light workout. When I mentioned this to a doctor, his attitude was "what do you want me to do about it?"
So, 30 years later and still suffering from the same (not worse) symptoms, I again mention it to a doctor. This time, he performs a blood test and tells me I have heart disease. What changed over that 30 years was that they now were able to diagnose and treat my problem. The heart specialist didn't want to hear that my disease was not progressive, but had been with me unchanged over those decades. That apparently didn't fit in with what he had learned in medical school.
After another decade passed during which I have been regularly checked by the US Veterans Administration doctors for side effects from agent orange, I find out that the VA now considers heart disease to be one of those side effects.
Ischemic Heart Disease and Agent Orange - Public Health
This is good news for those veterans without health insurance who have the same problem. However, I think that associating heart disease to agent orange was a political decision, not medical. My guess is they only know that heart disease could be caused by some environmental factor in Vietnam. If agent orange were the cause, then it stands to reason that the Vietnamese, especially the country farmers, would have a much higher incidence of heart disease. The incidence of heart disease there is actually about one third that of the industrialized countries. And Vietnamese farmers have a much lower rate of heart disease than the country in general.
I had, over the years, attributed my heart problems to two years of consuming Army field rations, which were loaded with chemical preservatives in order to give them a shelf life of nearly forever. For the time being, I'm sticking with that analysis.