Comment by alexk307

In the reference period 1999->2020, the instruments used by NHANES to track this data changed at least 3 times, they don't account for other changes to the general population that increase bicarbonate levels in serum (i.e. Number of obese Americans rose by ~40% in the reference period [1]). I'm not entirely convinced that using a proxy for C02 levels that can be confounded by a multitude of other health conditions that are common in the American population is a good way of going about this.

[1] https://www.niddk.nih.gov/health-information/health-statisti...