You may have seen recent press citing a new study linking the proton pump inhibitors (such as Nexium and Prilosec) and kidney disease. If you're taking one of these medications, don't worry. Your kidneys are OK.

We've been here before. I previously addressed the dubious claims of a very poor study linking PPIs with heart disease. That study received way too much attention, but has since been appropriately discredited. The current study is superior in terms of execution and methodology, but still has major limitations. Let's take a quick look.

The authors reviewed 2 large patient databases (1 from a long-term heart disease study, the other from a large healthcare system in Pennsylvania). The goal was to identify an association between PPI use and decline in kidney function (known as chronic kidney disease). This is a purely observational study looking back at existing data. Here's what you need to know:

Among PPI users in the first database, the 10-year risk of kidney disease was 11.8%, compared to 8.5% in non-users (3.3% absolute difference). The difference was 15.6% vs. 13.9% (1.7%) in the second database. These were statistically significant differences but are relatively small. (Ignore the reports stating a 20% or greater risk with PPIs, which refers to relative, not absolute risk, which is misleading)
By definition, a study of this kind cannot prove cause and effect. It can only show an association.
It is notoriously difficulty to study the association between PPI use and particular diseases. The reason is that people who take PPIs are inherently different than those who do not. In this study, those persons on PPIs were more likely to be obese, have hypertension, and use additional medications. And there were likely other, unaccounted for differences. It is nearly impossible to isolate the true effect of PPIs, even with complex statistical methods.
PPIs are available over the counter, so many people in the 'non-PPI' group probably used them at some point without reporting it. This further complicates the study methodology.
With any study, even an observational one, a sound hypothesis is essential. The authors of this study don't provide a logical hypothesis for why PPIs would cause chronic kidney damage. Mining large databases, in the absence of a hypothesis, is prone to error. Overall, we should be very cautious in interpreting these findings.
As a gastroenterologist, I admittedly have a biased perspective on this topic. That is because I treat many, many patients with real disease, who require PPIs. The PPIs are the treatment of choice for stomach ulcers, severe reflux esophagitis, and refractory heartburn. They prevent progression of Barrett’s esophagus. And they are extremely safe medications. We should always aim to reduce or eliminate any unnecessary medications. But it could be harmful to stop a necessary, and effective medication, based on suggested but unproven risks.

As always, speak with your physician if you have questions regarding this topic.

Christopher McGowan, MD, MSCR