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The claim:

I caught a segment about Diabetes Alert Dogs on of a TV show called The Doctors in my office's lunch room, and saw the following claim, which is repeated in an article on their website about the episode:

Dogs can predict blood-sugar-level changes 15 minutes before they’re caught by electronic monitors.

Is there any truth to that claim?


My own [10-minutes of] research on this topic:

I've only spent the rest of my lunch break looking into this, but I couldn't find much on Google to support that claim. I found this FAQ on dogs4diabetics, which provides a possible anecdotal reason (emphasis mine):

Our experience indicates that the identifiable changes in a diabetic’s chemistry derived from his breath or sweat precedes the measurable change in blood sugar currently measured by glucose meters by 15 to 30 minutes.

More substantially, I also found this 2016 study from the Journal of Diabetes Science and Technology which looks at the accuracy of diabetic alert dogs. I mention this study, because the methods include observing a dog alerting up to 10 minutes before a hypoglycemic event detected by a Continuous Glucose Monitoring (CGM) device (presumably the "electronic monitors" that the claim in question is referring to). From the Methods section of the study (emphasis mine):

We defined sensitivity [of dogs to detect a hypoglycemic event] as the mean proportion of CGM-captured hypoglycemic events where the dog alerted from 10 minutes before to 30 minutes after the first CGM measurement below 70 mg/dL. The lead-in time was chosen to approximate the known lag in CGM measurement relative to venous glucose.

I don't have a strong enough understanding of the study to know how to interpret the results, but the primary outcome states (again, emphasis mine):

Trained dogs provided a timely alert (within 10 minutes before to 30 minutes after onset of hypoglycemia) in 36% (sensitivity) of all hypoglycemic events.

But the conclusion in the abstract states:

CGM often detects hypoglycemia before a trained dog by a clinically significant margin.

I'm not sure if that should be interpreted as "sometimes a DAD can detect a hypoglycemic event 10 minutes before a CGM".

The study also states that there is a known lag with CGMs detecting a hypoglycemic event, and perhaps this is the "15 minutes earlier" that the claim is referring to? IE: "there is a known 15 minute lag for CGMs, but DADs are instant. Therefore, DADs can detect hypoglycemia 15 minutes before a CGM".


Unstated premise:

Obviously, this all hinges on the idea that dogs can be used to detect a drop in blood sugar levels in the first place. I found this question from 2015 about dogs detecting hypoglycemia here on skeptics.SE, as well as the JDST study I quoted above. From what I can gather in the short amount of searching I've done, it seems that the idea isn't absurd, but we don't have enough research to say very much with confidence, and the accuracy/reliability of these DADs is not very high.

The JDST study seems to conclude it's feasible, but very prone to problems. The two positive excerpts from the conclusions are:

While using trained dogs to detect hypoglycemia appears feasible, providers and patients should be aware of the considerable limits of their utility.

and

Trained dogs often alert a human companion to otherwise unknown hypoglycemia

The study also states that:

This is the first study evaluating reliability of trained dogs to alert to hypoglycemia under real-life conditions.

  • 3
    To clarify your confusion about the mention of a "known lag with CGMs", CGMs monitor glucose levels in interstitial fluid rather than the actual blood glucose level (which can be directly measured with a traditional "finger-prick" glucose meter). The glucose level in interstitial fluids lags behind actual blood glucose levels because it takes time for the change in blood chemistry to propagate through the surrounding tissue. – Dave Sherohman Sep 12 '17 at 8:39
  • And keep in mind that people with a blood glucose meter tend to use it only a few times a day or in cases where they have reason to be worried already. A dog's nose works permanently. So what you're probably really asking is whether a dog can smell the onset of a hypo before the patient himself notices it. – jwenting Sep 12 '17 at 8:47

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