E is essentially saying that in the 24 yr study, those who had high intake of beta-carotene rich foods, who were less likely to die from cancer/heart disease, had a a smaller percentage of them who smoked cigarettes and those who had low intake of beta-carotene, who more likely to die from cancer/heart disease, had a bigger percentage of people who smoked cigarettes. And that could be a reason why the people from the 12 yr study had no affects from the beta-carotene supplements because it wasn't the beta-carotene intake that affected them it was actually whether or not you smoked cigarettes.

Thus solving the discrepancy of the results between both studies.