Gap results in an estimated 7,000 deaths each year among people of color from heart disease alone...is that number calculated correctly?
According to their paper, the relative risks in Ischemic Heart Disease mortality from increasing NO2 concentrations by 4.1 ppb is 1.066. This came from the 2003 paper by Jerrett et al.
Reading the Jerrett paper we are told:
All RR estimates are given over the interquartile range of each pollutant.This value of 1.066 was calculated for the NO2 concentration values between Q1 and Q3
If you look at the Table in the Jarrett paper we see this:
Q1 therefore is the value for NO2 at 25% and Q3 is the value for NO2 at 75%.
Q1 = 10.21
Q3 = 14.33The difference between Q1 and Q3 is 4.1 ppb.
The RR they calculated for 4.1 ppb is 1.066.
This would lead us to conclude that those who had NO2 exposure between 10.21 and 14.33 had a 6% increase in risk of ischemic heart disease IHD mortality.
Now for me, when I look at stuff like this, I try to look at it collectively. The mean - average - from the Excel file is at the Q1 value in the Jarrett paper.
What I see when I look at this data, is if the IHD is "109 deaths per 100,000 people," that rate takes into account this exposure range. And that value includes the deaths of whites and nonwhites.
The claim of Clark et al, is that "gap results in an estimated 7,000 deaths each year among people of color from heart disease alone."
That value of 7,000 deaths is based on the author's assumption that every nonwhite in the US lives in areas where the N02 concentration is at 14.5 ppb. This assumption - using the Jarrett data for California, places every nonwhite in the US in the forth quartile for distribution.
In other words, based on the Jarrett Table 2 data, 25% of the distribution of NO2 by population contains 100% of the nonwhite population.
That...that cannot be what the Clark et al folks are saying...or is it?
Follow me on my analysis here, just to make sure I am seeing this correctly...
Relative risks (RR) for NO2 concentrations experienced by nonwhites and whites calculated using: RR = exp(βc), where c is the NO2 concentration (units: ppb), and β = ln(1.066)/(4.1 ppb) = 0.0156 ppb-1.They then show these calculations:
I think there is an error in this calculation. The second calculation is for the amount of IHD deaths anticipated for whites which should be divided by 1.167 and not 1.254. If I understand their thinking on this, they are comparing one population at an RR of 1.254 (nonwhites) to one at 1.167 (whites).
If I am correct, then the white IHD deaths would be 13,570 for a difference of 5,638 IHD deaths per year.
That amount, however, assumes that the entire US population of nonwhites is exposed to 14.5 ppb of NO2 while the entire population of whites is exposed to 9.9 ppb NO2.
To me, this calculation of 7,000, or 6,579, or 5,638 is not within the realm of reality. Could NO2 contribute to 5,000 plus IHD deaths per year? Yeah...that's possible if Jerrett's RR of 1,06 is a direct result of an increase in NO2.
That's not what Clark et al are wanting to convey:
Gap results in an estimated 7,000 deaths each year among people of color from heart disease aloneThey assert that compared to whites, 7,000 more deaths from IHD happen because of NO2 concentrations for this group being 4.6 ppb higher than what whites are exposed to.
That high of a "gap result" is not supported by their data.
So what does the data they present actually tell us?
Next post: Part 4: Preventing 7,000 deaths from heart disease alone among nonwhites each year