I live in one of the high income economies (Australia) which I think is not in the cohort. I wish it was clearer how the cohorts line up, by economy. The chart obscures this a bit.

My take-away is that the opiod and other health crises are real, and there is a real measureable effect but I am less sure health outcomes by high-income worldwide is in net decline, measured by life expectancy.

https://www.bmj.com/content/362/bmj.k2562#F2 are the figures which show six economies this didn't happen in:

Finland, Japan, Norway, Australia, Canada, Denmark