I asked, “Why have the CDC [big-kill] estimates not fallen?”
My question was based on a research study that Dr. Cole and I published a year earlier in Nicotine and Tobacco Research (abstract here ), showing that “there were 402,000 deaths attributable to smoking in 1987 and 322,000 in 2002.” We noted that despite the substantial decline in smoking prevalence, the estimate of smoking-attributable deaths from the Centers for Disease Control and Prevention had changed hardly at all. Five years later, my question is still relevant. The answer is clear: The CDC chose not to acknowledge the fact that deaths had plummeted.
Brian Rostron, a scientist at the FDA, has now published a study, also in Nicotine and Tobacco Research (abstract here ), demonstrating that smoking-attributable deaths declined from 398,000 in 2000 to 370,000 in 2007.
As I explained in my Cato article, most people mistakenly believe that CDC officials actually count the number of smokers who die each year. The truth is that the CDC uses a model that estimates the number of current and former smokers based upon data in the National Health Interview Survey (NHIS); the CDC subjects those smoker estimates to relative risks developed by the American Cancer Society in the 1980s, and then produces an estimate of the number of deaths that would not have occurred if they had never smoked. Like any model, the quality of the output is dependent on the quality of the input.
I had noted that the CDC was using 20-year-old data to produce its “big-kill” estimates; Dr. Rostron concurs, saying that “the CDC has not substantially revised the methodology or data that are used in this procedure since their introduction in the 1980s.”
Rather than using decades-old risk estimates, Dr. Rostron updated the relative risks for smokers and former smokers by calculating them from NHIS subjects from 1997 to 2004 who were followed through 2006 with linkage to the National Death Index. Unlike the outdated CDC estimates, he adjusted risks for age, race/ethnicity, education, alcohol consumption and body mass index, which are important confounding factors for some or all smoking-related diseases.
Here are Dr. Rostron’s big-kill estimates:
Although declining, Dr. Rostron’s big-kill numbers may still be too high because of the way he estimated deaths among former smokers. Using his model, former smokers accounted for about 177,000 out of the 370,000 deaths from smoking in 2007. This seems to be excessively high, as the 2007 NHIS documents that 60% of the 39 million former smokers had quit over 15 years previously. Any excess risk for a smoking-attributable death was minimal to nonexistent in this group.
Dr. Rostron’s deaths among former smokers were likely concentrated in those who quit less than 5 years earlier, and who therefore have risks similar to those of current smokers. But it is inconceivable that this group of 6.3 million former smokers produced almost as many deaths as the 27.5 million current smokers in 2007. Dr. Rostron’s model should be revised to reflect the different risks among former smokers who have short or long quitting histories.
Regardless, the main message of this study is valid: Smoking-attributable deaths have been in decline for over a decade. This is good news that the CDC and other federal agencies have ignored for far too many years.