This month, Dr. Sydney Spiesel discusses SIDS and pacifiers, a vaccine for cervical cancer, a new treatment for kidney stones, and a surprising explanation for the rise of a killer germ. (Click here and here for the last two roundups.)
Pacifiers: Do they prevent SIDS?
The mystery: For a long time, Sudden Infant Death Syndrome has been—and to some extent remains—a horrible epidemiological mystery. Babies die unpredictably and for no apparent reason, and medical science can almost never identify a cause. Yet it is tantalizingly obvious that SIDS is caused by something in a baby's environment, because the deaths are not randomly distributed. The rate varies with the seasons, is increased by parental smoking, and at times has been greater in some countries than in others.
Clue No. 1: The turning point in our understanding of SIDS came in 1986 with the publication of the first of several papers by S.M. Beal. Based on research done in South Australia, Beal established—not for the first time, but definitively—that it is dangerous for babies to sleep face-down. The rate of SIDS was unusually high in Australia, almost certainly because babies customarily slept face down on a sheepskin thrown atop a crib mattress. Soft surfaces, especially deep furry ones like sheepskins, magnify the dangers of face-down infant sleeping. The risk isn't that the baby will suffocate (as any TV crime-show watcher can tell you, suffocation causes changes that an autopsy can detect, which isn't true of SIDS). Instead, the most plausible explanation is that babies who die of SIDS in some way re-breathe exhaled air, and with it excess carbon dioxide.
Bonus mystery: Understanding the role of face-down sleeping in SIDS helped explain related epidemiological mysteries. Why, for instance, did the Netherlands experience a sudden and sustained tripling in the rate of SIDS beginning in about 1973? At the time, doctors suspected a mysterious virus or a change in a vaccine or medication. But the correct explanation, which came to light after sleeping-position studies like Beal's were conducted, was that in 1972 the Dutch government began supplying parents with a new edition of a baby-care pamphlet that instructed parents to put their babies to sleep face-down. (The idea was that this would diminish the risk of choking, which in fact is minuscule.)
Clue No. 2: Holland has, of course, stopped advocating face-down sleeping. There (and everywhere else) the rate of SIDS has dropped a lot since the "back to sleep" campaign was started. But SIDS has not disappeared and doctors continue to look for ways to further decrease it. De-Kun Li and colleagues, writing in a recent issue of the British Medical Journal, compared the sleeping habits of 185 California children who died of SIDS with the sleeping habits of a cohort of randomly chosen infants matched for age and maternal ethnicity. They focused on whether the babies went to bed with a pacifier—and found that those who did were at a reduced risk of SIDS of more than 90 percent.
Resolution: Since we know so little about the underlying mechanism of SIDS, it is foolish to speculate about why this is so or even whether pacifiers themselves (as opposed to something associated with their use) cause the reduction in risk. But I must say that Li's study reinforces my long-standing support for pacifiers. I've never believed that they interfere with breast feeding, and I generally favor any practice that makes a child happy. It's nice to have my indulgent instincts acquire authoritative support, however irrationally.
A vaccine for human papilloma virus: Will kids get it?
The disease: Cervical cancer almost always starts as a young person's disease. It isn't cancer early on, just a virus infection transmitted sexually or through skin-to-skin contact. Usually, the virus fades away over time and does no harm. Which is fortunate, since over time about three out of four sexually active women catch this virus—the human papilloma virus —most in the first five years after they become sexually active. HPV will be transmitted 5.5 million times in the United States this year, with younger people at greater risk. But it will result in only about 10,000 cases of invasive cervical cancer, 40,000 cases of noninvasive cervical cancer, and fewer than 4,000 deaths. If you become infected with HPV, your risk of cancer will depend largely on which strain you have. Other factors include age, genetics, whether your immune system is suppressed as a result of infection or medication, and luck.
Vaccine: Because cervical cancer is a viral disease like measles, mumps, and smallpox, it seems plausible that a vaccine could prevent it. And that now appears to be true. Two candidate vaccines, one (Gardasil) made by Merck and the other (Cervarix) made by GlaxoSmithKline, are being evaluated for FDA licensing or will be soon. Final testing of the Merck product was described at the recent annual meeting of the Infectious Disease Society of America and sounded impressive, indeed. More than 12,000 women from 13 countries were enrolled in Merck's clinical trial. Half were immunized with Gardasil and half were treated with a placebo. There were no cases of cervical cancer or precancerous conditions in the immunized group, compared with 21 cases in the placebo group.