I assume that what you mean by “descriptive” and “prescriptive” refers to ‘associative’ and ‘causative’ respectively.

You need to keep in mind that a clinical trial that investigates the impact of hypothesized lifestyle factors on health and life expectancy is practically impossible to conduct. We can’t force people to adhere to certain lifestyle habits for decades, and we can’t force a control group of people to abstain from those habits (unethical). Even if we could do that, the trial duration and the number of people to be enrolled are both prohibitively long and large.

So, trials like the one cited in my post are the next best option to investigate the possible causative correlations. In that respect, both quoted studies come as close as possible to the ideal. The lifestyle factors were assessed repeatedly during the follow-up periods.

But whether you trust the study results or withhold your trust, is of course, entirely up to you.