Thank you for letting me know about the link. It has been corrected in the article. Here it is:

https://academic.oup.com/eurheartj/article/42/15/1499/6213772

As for the limitations, I agree and that is the nature of an observational study. You are spot on with the education and income findings.

Funding was provided by the Capital Region of Copenhagen, The Danish Heart Foundation, The Danish Lung Association, Velux Foundation, and Lundbeck Foundation.

The primary point of the research paper and my article is manual labor is not a replacement for structured exercise. Granted, research is never one-size-fits-all.

There is a difference between constant physical activity and intentional activity with specified intensity levels and rests breaks.