[KarlKemp]

Always a good idea to get some sun, so do get out more! Crucially, Vitamin D gained via sunlight is significantly more effective for Vitamin D-related health improvements than supplements.

...which kinda points to the problem here: Vitamin D aka getting sunlight aka living an active life is almost impossible to control for.

Consider Bill Gates as an example for a healthy and active 65-year old man who seems to be spending a lot of time outside, considering their perennial tan. It would be perfectly believable for someone like that to have asthma, or well-controlled diabetes, or have had a bout with cancer 15 years ago without any of that having much of an impact on their daily lives.

Now consider an overweight, opiate-dependent patient of the same age, driving their mobility scooter through wall-mart and otherwise not leaving their couch much.

These two people are in the same category here except for Vitamin D levels.

It's also strange that the numbers do not seem to be representative of the larger patient population. Death rates, especially, are far higher. This isn't necessarily a problem, but it could be. One reason might be the limited availability of patients with data on Vitamin D levels. If so, the immediate suspicion is that testing depends on disease severity. Worst case, Vitamin D testing was previously done for some subgroup of patients: for example, levels might be routinely measured for lung cancer patients but not diabetics.

Finally, I'm somewhat suspicious of discretising the measurements into three classes. This obviously throws away part of the data for no immediately obvious reason. And intuitively, the difference between the two classes with Vitamin D deficits seems somewhat low?

[jbotz]

> Crucially, Vitamin D gained via sunlight is significantly more effective

Do you have any citations for that?

[cmrx64]

I can't back that statement up but sunlight has a suite of other non-vitD-synthesis effects too: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5086738/

[jbotz]

That's a very interesting paper! It has long been my belief that sunshine is good for you, and so long as you avoid an outright suburn, basically the more the better. Even with respect to cancer alone, from what I've seen in the literature over recent decades it seems undeniable that the reduced risk from various common cancers like prostate and breast cancer far outweighs the possible increased danger from skin cancer since melanoma is comparatatively rare and carcinoma not very dangerous; but mostly this is ascribed to Vitamin D and then taken as a recommendation for Vitamin D supplementation rather than increasing sun exposure. The sun, the primary source of life's energy on earth, remains mostly vilified by medical science.