Pets and your child’s immune system

I’ve said time and time again that solid science does not come from individual studies sitting all by their lonesome. Rather, it comes about as a result of a body of evidence. That isn’t to discredit any individual study that may be released, but instead to point out that the very nature of science is to discover and expose and correct for flaws. That cannot possibly be accomplished if one person or group comes up with a finding and everyone says, ‘Oh, good. Let’s just go with that.’ And that brings me to this recent study on children who live with dogs in their first year of life:

The study of nearly 400 children found that dogs were especially protective, and the babies who lived with dogs during their first year were about one-third more likely to be healthy during their first year, compared to babies who didn’t have a pet in the home. Babies with dogs in the home were 44 percent less likely to develop an ear infection, and 29 percent less likely to need antibiotics than their petless peers.

“Children who had dog contacts at home were healthier and had less frequent ear infections and needed fewer courses of antibiotics than children who had no dog contacts,” said the study’s lead author, Dr. Eija Bergroth, a pediatrician who worked at Kuopio University Hospital, in Finland, at the time of the study.

There is no reason to doubt the methodology of this study, as far as I know. There is no reason to doubt its integrity. This isn’t a highly complicated paper about kin selection or something of that nature where the logic can get quite counter-intuitive. This is a relatively straight-forward study, by all accounts. However, that does not mean it actually is better to have dogs around infants:

Previous research on pets in the home has suggested that animals, and dogs in particular, may provide some protection against the development of asthma and allergies. But, other studies have found that household pets may increase the number of respiratory infections in children, according to background information in the study.

Yet, on the flip side once again, this doesn’t mean it’s bad to have dogs (unless the child has allergies, of course). What this means is that there are some interesting results, both of which fit well into independent theories. For the previous studies, we know that animals carry plenty of germs and disease, so it wouldn’t be surprising to learn that they tend to transmit that sort of stuff to babies – basic germ theory. However, for this recent study, we also know that the immune system tends to do better when exposed to diverse environments early in life. That gives it a chance to build a working ‘knowledge’ of what it must resist. So which is the correct model?

We don’t yet know.

I personally lean towards it being better to have pets in the home, in part because dogs and cats are linked to greater happiness, which in turn is linked to a healthier body, but I’m not staking a claim to anything one way or another. The scientifically responsible thing to do here is to wait for a more robust body of evidence.

That’s how this whole thing works.

A basic of science

I often find myself reminded of a post I made on just the third day in the life of FTSOS. It was about a media report on a recent study that said a certain pesticide found in anti-bacterial soaps may actually contribute to the development of antibiotic resistance by bacteria. It was a fine study, but it was far from conclusive. (The news article wasn’t so cautious in its assertions.) Perhaps it would be best if people only used regular old soap, what with that not really qualifying as a real sacrifice, but as for the science, I was far from ready to say that that pesticide was a contributor to antibiotic resistance among bacteria in any significant way in the given environment.

And the reason is quite simple: science does not rely upon individual studies. Of course, we may be able to point back to the results from one lab or one group of researchers as published in a single study as the linchpin that opened up a whole new branch of study. But that doesn’t mean we believe that paper as being conclusive on its own. It only works when we have a body of evidence. In most cases that means a number of studies looking at the same or a similar problem and coming to the same or very similar conclusions. For a single paper that proves itself a linchpin, that means we need a number of other studies which use its findings as their basis. For instance, green fluorescent protein, or GFP, was shown to work as a marker of gene expression in a pretty definitive study. It has about a bajillion (rough estimate) other studies on it, but no one needed to reproduce the study which won one research team the Nobel Prize in chemistry. But people did use that study as a basis for about a gagillion (rough estimate again) studies. If the original study was wrong or faked or otherwise limited, we would be well aware of that by now because of all those subsequent studies. That is one way to compose a body of evidence.

To put this another way, take the studies on intercessory prayer and its efficacy. We have some that show positive results. Look, God is here to help! But then we have others that show negative results. Oh, no! God must be angry! And then we have a whole bunch which shows a null result. Uh…God must be indifferent. So how do we interpret these results?

Remember, we need to be looking at the evidence as a body. As one of those intolerant, bigoted, hate-filled evilutionist atheists, I would find it humorous if prayer gave negative health results. But I don’t get to have that laugh. Instead, I have to conclude that prayer has no detectable effect on health. None of the studies are conclusive; they suffer from bias, or are statistically insignificant in either direction, or just show a blatant null result. The most likely conclusion is that prayer does nothing. No study has convinced me otherwise, and most of the studies have shown prayer to be inconsequential to the well being of people anyway.

What I hope this post enables readers to do is recognize a fundamental aspect of how science works so that next time they see a study which concludes a link between this or that, they know what to think. That doesn’t mean it is okay to just dismiss a non-bias confirming study (i.e., a study that doesn’t give a result one likes). It just means that it is always necessary to look at the entire body of evidence before drawing a conclusion.