Randomized trials are the gold standard, but I wouldn't blast a study straight for being prospective. My main thingy with studies like these is that actuarial

Randomized trials are the gold standard, but I wouldn't blast a study straight for being prospective. My main thingy with studies like these is that actuarial bookkeeping is hard. The difference in base mortality rate between a few age years in difference can be huge. But since the study runs 4, that difference in base rate multiplies. Properly accounting for that is hard.