BY QUINN PHILLIPS | OCTOBER 24, 2022
For people with type 1 diabetes, maintaining an A1C level (a measure of long-term blood glucose control) below 7% — a widely recommended goal — can help prevent serious eye and kidney complications, according to a new study published in the journal Diabetes Care.
Diabetic retinopathy (eye disease) and chronic kidney disease are two of the most serious, and potentially disabling, complications that can develop due to elevated blood glucose levels over time. Diabetic retinopathy is on the rise worldwide, and without better detection and treatment efforts, it’s expected to contribute to widespread vision loss. While there are many promising treatments for retinopathy, the best way to avoid diabetes-related vision loss is to prevent eye complications in the first place — through blood glucose control, lifestyle measures, and possibly medical interventions like bariatric surgery or preventive drug treatments. Similarly, while treating diabetic kidney disease is critical, so are prevention efforts — including blood glucose control as well as lifestyle measures like dietary considerations and obesity prevention.
For the latest study, researchers followed 447 residents of southeast Sweden with type 1 diabetes from the time of their diagnosis before age 35, between 1983 and 1987, until 2019. Throughout this decades-long follow-up period, participants had their A1C measured, and researchers created a composite measure of A1C — known as long-term weighted average A1C — that they used to divide participants into five categories of long-term blood glucose control.
After 32 years of follow-up, 9% of participants had no retinopathy, while 64% had non-proliferative retinopathy (the less severe form) and 27% had proliferative retinopathy (the more severe form). When it came to an indicator of kidney disease involving protein in urine, 83% had no microalbuminuria (smaller amounts of protein in urine), 9% had microalbuminuria, and 8% had macroalbuninuria (larger amounts of protein in urine).
Near-normal A1C linked to reduced risk of complications
The researchers found that participants with weighted A1C indicting near-normal blood glucose levels did not develop proliferative retinopathy or macroalbuminuria. In fact, the lowest weighted A1C levels linked to developing these conditions were 7.3% for proliferative retinopathy, and 8.1% for macroalbuminuria. Among participants who fell in the highest category of weighted A1C, on the other hand — those with a weighted A1c level greater than 9.5% — 74% had proliferative retinopathy, and 44% had macroalbuminuria.
The researchers concluded that weighted average A1C from the point of a type 1 diabetes diagnosis is “a very strong biomarker” for predicting eye and kidney complications. To avoid these problems, they wrote, people with type 1 should aim for A1C levels below 7% and as close to normal as possible without experiencing hypoglycemia (low blood glucose) or a worse quality of life.
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