In our quest to control blood sugars of people who have diabetes, one of the ‘small blood vessel’ complications of diabetes that we are trying to prevent is damage to the kidneys. For people who have prediabetes, it has generally been thought that they do not have an increased risk of small vessel disease. However, there is mounting evidence that prediabetes may in fact cause small vessel damage; a new study suggests that prediabetes may in fact cause kidney damage.
First, let’s talk about what we mean when we say ‘prediabetes’. Diabetes and prediabetes are defined on the basis of how high blood sugars are. Quite simply, prediabetic blood sugars are lower than diabetic range blood sugars, but higher than normal blood sugars. For the exact blood sugar definitions in Canada, please see Table 2 (diabetes) and Table 4 (prediabetes) here.
A study suggesting that prediabetes causes kidney damage was published in the American Journal of Kidney Diseases. The study was a prospective cohort study that followed 1,261 people without diabetes between the ages of 50-62 for a median time of 5.6 years. Participants who had prediabetes at the start of the study were at nearly 2 times higher risk of having hyperfiltration (an early manifestation of diabetic kidney disease), and at 1.8 times higher risk of having higher-normal albumin levels in their urine, compared to those with normal blood sugars (albumin in the urine is also a diabetes-related kidney complication). These changes were seen independently of other risk factors such as blood pressure at baseline, and independent of changes in blood pressure medications.
That prediabetes can cause complications before diabetes develops has a profound impact, in that 1 in 4 Canadian adults has diabetes or prediabetes, with most of those being prediabetic. (In USA, 44% of American adults have diabetes or prediabetes). Most people with prediabetes do not know that they have this condition, as there are usually no symptoms of this condition.
While the notion that prediabetes can cause small blood vessel complications is relatively new, it is known that prediabetes (especially impaired glucose tolerance) are at a substantially higher risk of developing BIG vessel complications (eg heart disease).
Knowing that prediabetes can cause organ damage makes two things very clear:
1. We need to be checking for prediabetes in people who are at risk; and
2. We need to aggressively prevent and treat prediabetes.