(edit: this is now out of date. I now believe that intravascular albumin may be exponentially more important than sodium, as sodium does not posses intravascular specificity. Salt also has other negative properties. Also, this post is slightly out of context regarding DSPS, but I will likely write more about DSPS at a later date)
Here is a post a made on facebook. It seems my blog is a good place to paste it as well.
TLDR: Unless you have high blood pressure, try salt for sleep or apparent Delayed Sleep Phase Syndrome (DSPS).
Hey guys. At a recent doctors appointment, I noticed my blood pressure was on the low side (90/54). A couple of months ago, my blood pressure was normal (110/90). In retrospect, I have had symptoms of hypotension (e.g. vision darkening when standing up) even though my blood pressure was measured as normal. I noted such things on the sleep questionnaire, but the doctors didn't catch it, being useless as they are. The only reason I caught it is because I was lucky enough to take note of my slightly low blood pressure.
Looking up the relationship between hypotension and insomnia, I was only able to find one study. In patients with insomnia, 1/3 had hypotension. This hypotension was associated with symptoms I recognized in myself and from this group. In particular, the paradoxical "long-lasting increased excitability" was of interest.
Additionally, sleep deprivation may raise blood pressure, perhaps masking the diagnosis. Thus, even if your blood pressure is normal during doctor visits, you may have night-time hypotension.
I was able to find an article about a study regarding sodium intake and sleep, though I can't find the original research paper. A very low sodium diet (500mg) led to night-time awakenings and less sleep, whereas this was not a problem on a 2000mg diet. What's interesting is that during high sodium diet (5000mg) there was even fewer night-time awakenings and even more sleep.
For this reason, I started adding salt to my diet a couple of days ago (about 5g iodized salt, or 2000mg sodium). This is in addition to the sodium I was already consuming, so I might be getting 3000-4000mg total. I consume potassium above the 98th percentile, which is around the RDA of 4700mg. I probably consume 5000-6000mg potassium daily. This probably exacerbated the problem, but likely isn't a problem for anyone reading this. I've had sleep problems long before upping my potassium intake, though I don't know what my sodium intake was back then. I also had regular darkening/blackened vision upon standing, thus suggesting this may have been a long term issue.
So far, though it's too soon to say for sure, I'd say It's helping. It's only my third day taking salt. Please leave a comment if any of this sounds familiar, as there appears to be little scientific data available.
I suspect many people with DSPS attempt eating healthy in hopes that it will help. This, in turn, may lower blood pressure and actually make things worse, at least for 1/3 of us. Most people consume too much sodium and not enough potassium, but that's likely not as much the case for those of us trying to compensate for chronic problems with a good diet. If any of this sounds like you, try adding salt to your diet and see if it helps.
data, in sleep-disordered breathing patients, with a larger sample size than the other srudy, may put the number of insomniacs with
hypotension at a lower estimate, though they don't appear to measure
sleeping blood pressure as the other one did. Due to the disease criteria used, it may be entirely irreverent to insomniacs (though still worth noting), or it may be that the country it was done in has higher
blood pressures in general.