Sodium concentration in sweat

I can’t seem to find it now but there is a study in military personnel that found that their sweat sodium concentration decreased quite a bit if they were on a low salt diet for 3 months. Unfortunately, this review study (http://article.sapub.org/10.5923.j.sports.20180801.05.html) cites an article that finds that limiting dietary sodium hinders your ability to regulate body temperature and therefore get hard workouts in. So it may be that if you lower your dietary salt intake for months you can reduce your salt loss but it takes a while and your hard workouts might be hindered while you adapt.
There is quite a bit of evidence that your sweat glands do adapt and that almost everyone’s salt concentration in sweat decreases as they are exposed to heat.
In the medical realm, while we have found reducing dietary sodium reduces blood pressure there is also some evidence that it doesn’t work for everyone and some people are “salt sensitive” while others aren’t. So it may be difficult to find evidence as long as the idea of the study is to compare averages.