Long-term blood sugar levels, HbA1c, can be used to accurately determine the risk of a person with type 1 diabetes developing eye and kidney complications. A study from Linköping University, Sweden, has shown that this level should be less than 53 mmol/mol (7%). The study has followed people for more than 30 years after the onset of type 1 diabetes, and the results were published in Diabetes Care.
People with diabetes can suffer damage to the small blood vessels in various organs. The reasons for this are unclear, but it has been known since the 1990s that good control of blood sugar levels reduces the risk of complications. However, it has not been clear what long-term sugar level, HbA1c, people with type 1 diabetes should have to avoid serious damage to the blood vessels in the eyes and kidneys.
Summary
Aim
To evaluate HbA1c followed since diagnosis, as a predictor of serious microvascular complications (i.e., proliferative diabetic retinopathy [PDR] and nephropathy [macroalbuminuria]).
Methodology
In a population-based observational study , 447 patients diagnosed with type 1 diabetes before the age of 35 years between 1983 and 1987 in southeastern Sweden were followed from diagnosis until 2019. Long-term weighted mean HbA1c (wHbA1c) was calculated by integrating the area under all HbA1c values. Complications were analyzed in relation to wHbA1c classified into five levels.
Results
After 32 years , 9% had no retinopathy, 64% had no PDR and 27% PDR, and 83% had no microalbuminuria, 9% microalbuminuria, and 8% macroalbuminuria. Patients with near-normal wHbA1c did not develop PDR or macroalbuminuria.
The lowest wHbA1c values associated with the development of PDR and nephropathy (macroalbuminuria) were 7.3% (56 mmol/mol) and 8.1% (65 mmol/mol), respectively. The prevalence of PDR and macroalbuminuria increased with increasing wHbA1c, being 74% and 44% in the highest category, wHbA1c > 9.5% (> 80 mmol/mol).
Compared with follow-up after 20-24 years of duration, the prevalence of PDR increased from 14 to 27% and that of macroalbuminuria from 4 to 8%, and both appeared with lower wHbA1c values.
Conclusions wHbA1c followed since diagnosis is a very strong biomarker for PDR and nephropathy, and the prevalence of both continues to increase 32 years after diagnosis. To avoid PDR and macroalbuminuria in patients with type 1 diabetes, HbA1c <7.0% (53 mmol/mol) should be recommended and as normal as possible when it can be achieved without severe hypoglycemia and with good quality of life. |
Comments
“Our study accurately determines long-term sugar levels that can avoid complications. This knowledge can increase a person’s motivation to keep their blood sugar under control,” says Hans Arnqvist, professor emeritus at Linköping University and leader of the study.
Researchers in the current study, known as VISS (Diabetic Vascular Complications in South-Eastern Sweden), have followed all children and adults under 35 years of age who developed type 1 diabetes during the period 1983-1987 and who received care in South-East Sweden. -East Healthcare. Region of Sweden. All 447 people newly diagnosed in the region during this period were included in the study. Researchers have tracked patients’ HbA1c values, which reflect their average blood sugar levels over a longer period. They have also monitored the development of eye and kidney damage in these patients for a period of between 32 and 36 years after diagnosis.
The small blood vessels in the eye are particularly susceptible to damage in type 1 diabetes. Almost all patients experience small hemorrhages in the eye that do not affect vision. In some cases, new blood vessels develop in the retina. The latter is known as "proliferative retinopathy" and can lead to blindness. Another effect of diabetes concerns the area known as the "macula" of the retina, where high-focus vision is found. Damage here leads to blurred vision.
The kidneys are not as sensitive to high blood sugar levels as the eye, but the important small blood vessels here can also be damaged. A consequence of such damage is the excretion of blood proteins in the urine. Albumin is the most concentrated protein in the blood, and when it is present in the urine, the condition is known as "albuminuria." Damage to the kidneys eventually leads to impaired kidney function and, in severe cases, kidney failure. This is a fatal condition if untreated, and the patient must undergo dialysis or receive a kidney transplant.
The blood sugar level in a healthy person is closely controlled, with a maximum HbA1c level of 42 mmol/mol (6.0%).
“The results of our study show that people with type 1 diabetes for at least 32 years must keep their long-term average sugar level below 53 mmol/mol (7.0%), if they want to avoid serious damage completely. . The risk of eye and kidney complications increases as the level increases. Our conclusions are related to avoiding complications derived from damage to blood vessels. But if a patient has problems with low blood sugar, hypoglycemia, it is not possible to control the blood sugar level so strictly,” says Hans Arnqvist.
The HbA1c target level suggested by the VISS study results is consistent with the individual targets recommended by the American Diabetes Association. In Sweden, target levels are given for groups, rather than individuals.
Previous follow-up by the research group was carried out 20 years after the onset of the disease. Now, after 30 years, the results show that the damage has arisen at lower blood sugar levels than after 20 years. More patients have experienced harm, despite having blood sugar levels that are no higher than they were previously. In other words, it appears that the threshold for developing complications gradually decreases over time. This means that the study does not allow conclusions to be drawn about recommended blood sugar levels for people with type 1 diabetes more than 30 years after diagnosis.
The VISS study has received funding from the Swedish Childhood Diabetes Foundation and the Östergötland Region Foundation Funds.
