When studies sampling larger populations finally appeared, the reported declines in heart attacks began to shrink. A study of the Piedmont region of Italy found a much lower decline of 11 percent, though curiously only for residents under 60 years of age. England, which implemented a smoking ban nationwide, presented the first opportunity to study the matter on a national scale. Researchers there credited the ban with a heart attack reduction of just over 2 percent nationwide.

Critics noted that the rate of heart attacks in England had also been falling in the years prior to the ban and that the reason for the decline was still not clear. Regardless, the data there made it obvious that the miraculous reductions claimed in smaller studies were unrealistically high. Even so, despite acknowledging the wide variation in findings and the admitted methodological limitations of the studies, a 2009 meta-analysis conducted by the Institute of Medicine concluded that the impact of smoking bans on short-term heart attack rates was real and substantial: “Even a small amount of exposure to secondhand smoke… can cause a heart attack,” one member of the IOM panel informed the New York Times, urging that “smoking bans need to be put in place as quickly as possible.”

This report had, however, omitted one of the largest studies of secondhand smoke and heart attacks conducted to date. A 2008 study covering the entire country of New Zealand—a population smaller than England’s, but bigger than the American towns previously studied—found no significant effects on heart attacks or unstable angina in the year following implementation of a smoking ban; hospitalizations for the former had actually increased.