Calcium Levels Effect Sleep?

I just had someone comment to me last night that the level of calcium in your blood can effect your sleep, i.e. if your calcium in low, you will not sleep well.

Has anyone else heard this? Any experience with this? I don't know how reliable my "source" was, so I thought I'd ask here.

Also, if it is true, does anyone know of a brand of good calcium supplement that does NOT contain magnesium? Personally, I cannot take magnesium supplements. It is one of the few migraine triggers I've been able to pinpoint.

Thanks for any input!
jbn