A 20-year prospective follow-up study to evaluate the development of retinopathy and nephropathy after the onset of type 1 diabetes mellitus: Contribution of glycemic control and metabolic memory

Aim. To assess the time course of changes in the level of glycated hemoglobin (HbA1c) for 20 years after the onset of type 1 diabetes mellitus (T1DM) and to compare its correlation with the development of microvascular complications, such as diabetic retinopathy (DR) and diabetic nephropathy (DN). Subjects and methods. A total of 187 children with new-onset T1DM were registered in Moscow in 1994. During the 20-year follow-up study, these patients underwent regular check-ups at the Endocrinology Research Center, Ministry of Health of the Russian Federation, which included assessment of physical data, HbA1c 2-4 times a year, biochemical blood and albuminuria tests (once per year), and ophthalmologic examination (twice a year). A total of 155 people fully completed the 20-years follow-up study. Results. During the 20-year follow-up period after the onset of T1DM, 86 of the 155 patients developed microvascular complications: DR and DN in 86 (55.5%) and 24 (15.5%) cases, respectively; while DR concurrent with DN were noted in 20 patients. By the time of their last visit, 69 (44.5%) patients had no evidence suggesting the presence of microvascular complications. The level of HbA1c at the onset of the disease in patients who later developed the complications was higher than in those without complications (10.2±0.6 and 8.5±0.2%, respectively (p = 0.003). The statistically significant differences in HbA1c levels between the groups persisted during subsequent 15 years of follow-up, averaging 9.2±1.5, 9.7±0.9, and 8.1±0.7% after 5, 10, and 15 years, respectively, in the complication group and 7.1±0.3, 8.1±0.4, and 7.2±0.2% in the non-complication group (p < 0.01). Over the last 5 years of the follow-up, the mean HbA1c level between the groups was not significantly different, which at the end of the 20-year follow-up period was 7.8±0.3 and 7.4±0.6%, respectively (p > 0.05). The mean duration of T1DM, in which DR developed, was 9.6±6.2, 11.0±2.0, and 13.6±4.6 years for the non-proliferative, pre-proliferative, and proliferative stages, respectively. That of T1DM, in which DN developed, was 11.8±0.6 years for microalbuminuria and 16.1±1.3 years for macroalbuminuria. Conclusion. The 20-year clinical follow-up of patients who had fallen ill with T1DM in childhood showed that diabetic microangiopathies developed with the long-term preservation of poor blood glucose control (BGC) starting at the onset of the disease. At the same time, the complications progressed to more severe stages, despite a clear trend toward better BGC. This may be suggestive of the negative metabolic memory phenomenon, which necessitates stable BGC, starting at the onset of the disease, for the prevention of microvascular complications.

type 1 diabetes mellitus, microvascular complications, glycated hemoglobin, negative metabolic memory, prospective clinical follow-up