Docs get so hung up on matching the numbers on patients' charts to mainstream guidelines that they often forget these things are written on paper -- not set in stone.

But in addition to being meaningless, many of those targets are actually dangerous -- and quite possibly deadly.

Case in point: blood pressure.

The guidelines are often meaningless to healthy people, and a new study shows how they could be dangerous and even deadly for stroke victims -- because meeting those targets could actually boost the odds of another stroke.

Researchers reviewing data on more than 20,000 stroke patients found that those who had systolic readings -- that's the top number -- of below 120 had a higher risk of second stroke than people who were between 130 and 140.

To put that into perspective, below 120 is right on target -- at least as far as the mainstream is concerned, and there's even talk of lowering that target to 115. Meanwhile, 130-140 is considered "prehypertension" -- and many docs now prescribe BP meds for people in this range.

What's more, patients who had the technically perfect systolic reading of under 120 had only an ever-so-slight decrease in the risk of another stroke when compared to patients with readings between 140 and 150.

That's flat-out hypertension, at least if you're following guidelines. And if that's not the surest sign we've gone overboard with all this worry over blood pressure, I don't know what is.

The researchers behind the new study aren't quite ready to abandon those guidelines -- they suggest waiting six months after a stroke to lower BP levels.

But why bother, especially in borderline cases? In addition to being harmful to stroke victims, studies have shown there's not much benefit for healthy people.

One study earlier this year found the entire prehypertension category -- systolic readings between 120 and 140 -- to be essentially meaningless. Patients under the age of 50 didn't face any increased heart risk until their systolic numbers topped 200 -- while the over-50 crowd didn't see increased risk until they reached 140.

Read more about that here.

So forget 120 and don't even think about 115 -- those numbers may have succeeded in getting more people onto BP meds, but they haven't succeeded in saving lives.