In the late 1970s, the World Health Organization launched a research project known as MONICA, for “MONItoring CArdiovascular disease,” that was similar in concept to Keys’s Seven Countries Study but considerably larger. The study tracked heart disease and risk factors in thirty-eight populations in twenty-one countries—a total population of roughly six million people, which unlike previous studies included both men and women. Hugh Tunstall-Pedoe, the MONICA spokesman, has described the project as “far and away the biggest international collaborative study of cardiovascular disease ever carried out” and noted that, “whatever the results, nobody else has better data.” By the late 1990s, MONICA had recorded 150,000 heart attacks and analyzed 180,000 risk-factor records. Its conclusion: heart-disease mortality was declining worldwide, but that decline was independent of cholesterol levels, blood pressure, or even smoking habits.

The MONICA investigators suggested reasons why their study might not have confirmed Keys’s hypothesis, among them the possibility, as Tunstall-Pedoe noted, that with populations “the contribution of classical risk factors is swamped by that of other dietary, behavioral, environmental, or developmental factors.” He also discussed something that may have contributed initially to the widespread belief in Keys’s hypothesis: the tendency to publish or pay attention to only that evidence that confirms the existing beliefs about heart disease and risk factors. “If you do a study in your population and you show a perfect correlation between risk factors and heart disease, you rush off and publish it. If you don’t, unless you have great confidence in yourself, you worry that perhaps you didn’t measure something properly, or perhaps you’d better keep quiet, or perhaps there’s something you haven’t thought about. And by doing this, there is a risk of myths’ becoming self-perpetuating.” “There are people,” Tunstall-Pedoe said, “who want to believe that if we find anything less than 100-percent correlation between traditional risk factors and trends in heart disease, we are somehow traitors to the cause of public health, and what we say should be suppressed, and we should be ashamed of ourselves. Whereas we are asking a perfectly reasonable question, and we came up with results. That is what science is about.”