> He points out that the DASH study didn't conclude anything about death or cardiovascular disease. Yes, that's true. So sure, there's a chance that despite blood pressure reductions a low salt diet could cause problems. But it's not the obvious conclusion.
That's the whole point, you say it yourself. The idea that "salt is bad" has just as shaky underpinnings as "lower blood pressure is good". The only thing we care about is death or disease, not lowering blood pressure. So even if less salt = lower blood pressure, that doesn't tell us if this is good, or harmful.
The obvious conclusion is that there is no conclusion.
> The idea that "salt is bad" has just as shaky underpinnings as "lower blood pressure is good".
Wait, "lower blood pressure is good" has shaky underpinnings? Is there a debate on that? I don't think there's a debate that high blood pressure results in worse (death/disease) outcomes.
"Wait, "lower blood pressure is good" has shaky underpinnings? Is there a debate on that? I don't think there's a debate that high blood pressure results in worse (death/disease) outcomes."
There's no debate that high blood is associated with heart disease. There's always "a debate" if you try to go from correlation to cause. You always have to be careful this.
You have to show that a particular mechanism for lowering blood pressure results in better outcomes. You can't unambiguously say "we've lowered the blood pressure, we know the results will be better now".
"There's no debate that high blood is associated with heart disease. There's always "a debate" if you try to go from correlation to cause. You always have to be careful this."
I always thought that high blood pressure was caused by destruction of the lining of the arteries, and stiffening of the tissue, rather than water retention.
Control of blood pressure is dependent on this delicate balance of tissues against the pumping of the heart, as well as production of the substances that allow you to be sexually active.
Hence the fortuitous discovery of Viagra whilst searching for blood pressure control medications.
I acknowledge that jumping from a to b to c (low salt to low blood pressure to less death) has gaps in causality. But why do you not take objection to his uncited assertions that low salt intake and bad outcomes together imply causality?
So then it sounds like one might say that lower blood pressure isn't necessarily good unless you already have high blood pressure (or are on the cusp of having high blood pressure)?
Populations with low sodium intake, and other factors, have no hypertension, and low rates of death and disease from heart disease.
The randomized studies have found lower death and disease from lower sodium. So far the probability that this is just chance is about 10%. So the standard p number is not reached.
The most likely outcome is that a bigger better studies will produce significance.
Thank you for such precision concerning statistical semantics.
But I also find the non-experimental data compelling. I think more long term data will clear this up eventually.
It is urgent that we solve foundational debates in statistics. The health and economies of the world hang on this very point. So far Judea Pearl's work is the most compelling I've found. Do you have any references you'd suggest?
Because kidney function is damaged by pressure but its control mechanisms are governed by osmolarity (flow). A high pressure, low-flow kidney will send signals to the body to increase BP further, until the kidney essentially annihilates itself. You've got to unload the kidney down to a reasonable level, while keeping sufficient pressure to perfuse the heart and brain. In the setting of cardiovascular disease (stiff pipes with reduced cross-sectional area), the safe range becomes progressively narrower.
That's the whole point, you say it yourself. The idea that "salt is bad" has just as shaky underpinnings as "lower blood pressure is good". The only thing we care about is death or disease, not lowering blood pressure. So even if less salt = lower blood pressure, that doesn't tell us if this is good, or harmful.
The obvious conclusion is that there is no conclusion.