Nathanael Johnson of California Watch has breathlessly announced the results of his review of California hospital C-sections rates: For-profit hospitals performing more C-sections. Natural childbirth and homebirth advocates are trumpeting the news. Too bad they don’t realize that the study shows exactly the opposite of what Johnson claims. The association between the status of hospitals and their C-section rates is so weak as to demonstrate that there is no connection at all.
According to Johnson:
For-profit hospitals across the state are performing cesarean sections at higher rates than nonprofit hospitals, a California Watch analysis has found.
A database compiled from state birthing records revealed that, all factors considered, women are at least 17 percent more likely to have a cesarean section at a for-profit hospital than at one that operates as a non-profit. A surgical birth can bring in twice the revenue of a vaginal delivery.
That sounds impressive until you consider what constitutes a strong association.To understand why a 17% increase is essentially no increase at all, it helps to compare examples with strong associations.
Take smoking and lung cancer, for example. Smoking increases the risk of lung cancer by more than 2000%. How about homebirths? Homebirth advocates are fond of claiming that the increased risk of neonatal death at homebirth is trivial, but CDC statistics indicate that it is in the range of 200%. In contrast, a 17% increase in C-section rate between for profit and not for profit hospitals is so small as to indicate that there is no relationship at all.
Several years ago Gary Taubes wrote a piece for the New York Times Magazine explaining how lay people can judge the results of epidemiological studies, Do We Really Know What Makes Us Healthy? He was writing in the wake of new revelations about estrogen replacement therapy that showed that the benefits of estrogen had been vastly overstated. He pointed out that the estrogen fiasco was a foreseeable result of using weak epidemiological data to make sweeping pronouncements.
In the process, the perception of what epidemiologic research can legitimately accomplish — by the public, the press and perhaps by many epidemiologists themselves — may have run far ahead of the reality. The case of hormone-replacement therapy for post-menopausal women is just one of the cautionary tales in the annals of epidemiology. It’s a particularly glaring example of the difficulties of trying to establish reliable knowledge in any scientific field with research tools that themselves may be unreliable.
Tabues offered lay people rules of thumb for evaluating claims based on epidemiological data.
So how should we respond the next time we’re asked to believe that an association implies a cause and effect, that some medication or some facet of our diet or lifestyle is either killing us or making us healthier? We can fall back on several guiding principles, these skeptical epidemiologists say. One is to assume that the first report of an association is incorrect or meaningless, no matter how big that association might be… Only after that report is made public will the authors have the opportunity to be informed by their peers of all the many ways that they might have simply misinterpreted what they saw…
If the association appears consistently in study after study, population after population, but is small — in the range of tens of percent — then doubt it. For the individual, such small associations, even if real, will have only minor effects or no effect on overall health or risk of disease. They can have enormous public-health implications, but they’re also small enough to be treated with suspicion until a clinical trial demonstrates their validity (my emphasis).
Let’s apply Taubes’ principles to Johnson’s claim that for profit hospitals perform more C-sections.
1. Assume that the first report of an association is incorrect or meaningless: This is the first report of an association. It was prepared by a journalist and has not been peer reviewed.
2. If the association appears consistently in study after study, population after population: This is the first time that this association has been noted. There have been no similar studies, and, of course, there have been no studies of other populations.
3. If the association appears … is small — in the range of tens of percent — then doubt it: An increase of only 17% is so small as to be almost certainly meaningless.
According to these principles, Johnson’s finding of an increase of 17% actually implies that there is NO association between profit status and C-section rate. And that doesn’t even address the fundamental flaws in the actual analysis. First, the risk status of patients in hospitals may differ between for profit and not for profit hospitals in ways that were not taken into account in the analysis. Second, Johnson himself found that there was no correlation between the volume of high paying vs. low paying patients and the C-section rate. If profit were driving an increased C-section rate, hospitals that have more indigent and non-paying patients should have lower C-section rates, but they do not. Third, and perhaps most important, Johnson did not demonstrate any connection between the profit status of the hospital and the profitability of C-sections. His entire analysis rests on the assumption that hospitals make more money for C-sections, but there is no set rate for reimbursement for obstetric care. Hospitals make contracts with individual insurers that provide different compensation for the same procedures. Depending on the specific contracts, C-sections might be profitable if the patient carries insurance from Company A, but unprofitable if the patient carries insurance from Company B. Profitability depends entirely on whether the compensation for the procedure defrays the costs incurred for that procedure. Depending on the specific reimbursement rate, a C-section could actually be less profitable than a vaginal delivery, because a C-section requires far more resources.
As is only to be expected in any criticsm of C-sections, all the usual critics are involved or weigh in. One of the two experts that vetted Johnson’s analysis was Debra Bingham from Lamaze International, which has loudly and publicly bemoaoned the rising C-section rate. And the “expert” on C-sections who provided the accompanying Q&A is none other than Amy Romano of Lamaze, who has repeatedly demonstrated that she cannot analyze scientific research, misunderstands what she reads, and refuses to correct egregious errors in her written materials.
The bottom line is this: California Watch did NOT demonstrate an association between profit status and C-section rates. In fact, Nathanael Johnson’s analysis for California hospital C-section rates demonstrates exactly the opposite. A 17% increase in C-sections is so small as to be meaningless. In other words, Johnson demonstrated that there is NO association between profit status and C-section rate.
