Monday, January 21, 2008

Throw away your cold medicine?

A recent article in the New York times touts: "Seawater Seems to Beat Medicine in Fighting Colds." The article goes on to describe a study where "scientists assigned 289 cold or flu patients ages 6 to 10 to be given a nasal wash three times a day with water from the Atlantic Ocean that had been commercially processed but retained seawater’s trace elements and minerals. As comparison, a group of 101 children used ordinary over-the-counter cough and cold medicines."

The Times gets this first part wrong. The "seawater" group got both standard medications and seawater, as explained by the journal article on the study. So, right away, we are not talking about throwing away our cold medicines. Instead we might have to buy (for those of us not close to the ocean) seawater (more below about saline vs. seawater).

But the study does have some interesting results.

Here's the good part
The results for the preventative success are most striking: at week 12, 25% of the children in the control group had reported illnesses that caused an absence from school versus only 8% in the treatment group. This is statistically significant, meaning the results were too large to be explained away by mere chance. This does not mean, however, that biases in the study could not have caused the difference (no matter how statistically significant, bias, if it exists, can mean an otherwise statistically significant difference is spurious).

Here's the bad part
1. The study was not blind. This means that the children (and physicians and parents) were aware of whether the kids were taking the saline solution or not, subjecting the study to a "placebo" effect: kids who were taking the saline might have 'felt' better, but had no less incidence of a cold. The study's authors make an error in the journal article by stating: "the large number of participants, multi center design, and consistence of results between individual parameters (assessed by physician, patient, and parent) lower the risk of bias."

Bias is not mitigated by sample size -- that is, a large biased group is no better than a small biased group (imagine trying to figure out average height of all men by taking an NBA team, then doing a second study with the average of all NBA teams, saying this lessens the bias).

Similarly, having three biased parties (physician, patient, and parent) would only reduce the bias if we were comparing it to the bias of the most biased party (say, the parent).

2. The treatment is no fun.
Perhaps as important as the questionable effect of the study due to bias is the fact that the treatment involves the solution being squirted into the kid's nose 3 times a day for 12 weeks. I was sort of amazed that the study had so few dropouts (only 11 out of 401 patients in the study dropped out). The unpleasantness seems barely worth the avoidance of a cold or two.

3. Seawater, water or saline-- does it matter? The study does not provide any comparison of the seawater spray to other sprays, or even a simple water spray. To its credit, the journal article does not focus on the fact that the solution was seawater but instead on the comparison of nasal wash versus no nasal wash. In the journal article, there is little indication that seawater would be any better than salt water (the word seawater is mentioned 10 times in the journal article as opposed to saline, which is mentioned 64 times). BTW, the seawater in the study was processed (and presumably sterilized), so don't take it literally and go to your neighborhood polluted beach for your solution.

The Times article, however, focuses on the idea of seawater, as opposed to a simple saline (salt-water) solution.

Net Net
It does seem that washing your nose out with saline 3 times a day will make your kids feel better and they will miss less school. But it's unclear whether they are actually any less sick or they just think they are less sick (to that end, maybe giving them a sugar pill each day, telling them it was a special cold pill, would have the same effect).


Ira Skop said...

I've never tried it myself.

Steven Salzberg said...

Actually there is a possible cause for salt water preventing some "cold" symptoms. Salt doesn't prevent any viruses from infecting you, but it does kill Streptococcus bacteria quite effectively. So if some of the illnesses were strep infections, then a high-salt rinse might reduce the bacterial load.

On the other hand, salt doesn't hurt staph at all, so if you have a staph infection it can actually get worse if you wash it with salt water. That's because you can kill other bacteria and make it easier for the staph to thrive.