Do continuous glucose monitors (CGMs) really help patients with Type 2 diabetes? Phil Galewitz, a reporter for Kaiser Health News, has written a thought-provoking article discussing the doubt that some experts harbor on the issue.
Many in the diabetes world—doctors, patients, and advocates alike—have long assumed that CGMs could provide a benefit to patients with Type 2 diabetes (T2D). CGMs can provide nearly immediate feedback on the blood sugar impact of diet, exercise and other lifestyle choices, actionable data for patients hoping to improve their glycemic control. The technology has already been eagerly embraced by the Type 1 diabetes community, the first patients to whom it was made available.
But Galewitz writes that “the few studies — mostly small and paid for by device-makers — examining the impact of the monitors on health [of patients with T2D] show conflicting results in lowering hemoglobin A1c.”
There’s certainly evidence on each side of the ledger. An article published by AJMC asserted that “clinical study results demonstrate that CGM in T2D is powerful for behavior change,” with reference to studies showing that CGM use resulted not only in A1c reductions but in less hypoglycemia, decreased caloric intake, and increased exercise rates. An editorial in American Family Physician, by contrast, refers to several studies showing that CGMs conferred little or no benefit.
Galewitz also points to a “landmark” 2017 study that concluded that for patients with non-insulin-treated T2D, there was no benefit to blood sugar monitoring. In this experiment, 418 North Carolina patients were told to monitor their blood sugar once daily, or not at all. A year later, there was no significant difference in their A1c levels.
We would object to the relevance of this study. For starters, by filtering out participants that required insulin or had really uncontrolled diabetes (A1c > 9.5%) the study did not consider the patients most likely to benefit from blood sugar monitoring. But more importantly, a once-daily blood sugar check cannot possibly inform a patient about the impact of individual decisions (eg, how much this piece of toast might raise one’s blood sugar, or how much this walk might lower it). A single daily blood sugar value is not in any way an approximation of the type of data that a CGM provides.
Nevertheless, as we’ve seen in the T1D community, the devices themselves do not improve glycemic management automatically. It’s not a silver bullet. A CGM only gives its user better data; the user must choose to do with that data.
One thing that everyone agrees on is that cost will be an issue. After some hesitation, insurance companies have now mostly agreed to cover CGMs for people with T1D. But it will be a tougher sell to get them to pay for the same technology for patients with Type 2 diabetes, especially those that do not require insulin, as they tend to have less volatile blood sugar and therefore have a less critical need for the technology. The cost will almost certainly need to come down before insurers agree to reimburse.
Manufacturers are betting that it will happen, ramping up production capacity and trying to reduce prices. And consider Dexcom’s recent Super Bowl ad, featuring rock star Nick Jonas: it could only have been meant to speak to the approximately 34 million Americans with T2D, and not the mere 1.6 million with T1D, most of whom are already well aware of the technology. Tellingly, the ad portrayed its device as “diabetes” technology, not specifying any type.
There still haven’t been any large, long-term studies of the CGM’s potential to improve Type 2 diabetes outcomes. Even if doesn’t make sense for all T2D patients to wear a CGM continually, we are optimistic that the technology can still find a role to play in the standard of care. When we spoke to Dexcom CEO Kevin Sayer, he told us that his business has explored different models of use for those with Type 2 who are not taking insulin:
“We’ve been trying to come up with models and analytics around our device in that population. Does a patient need four a year? Do they need one a year? Do they need one a month?”
“Not all Type 2 patients need a behavioral change and not all of them need pharmaceutical change, but it’s really easy to tell which ones need which when you put them on a CGM. You could never find that out with fingersticks in a million years.”