5年間のHbA1c値の推移と糖尿病網膜症の発症率

Correlation of hemoglobin A1c levels and onset of diabetic retinopathy over a five-year period

　初診時，網膜症を認めない187例のインスリン非依存型糖尿病（NIDDM）患者のHbA_1c値を5年間測定し，網膜症の発症率をHbA_1c値の推移パターン別に算出し，罹病期間，治療内容の影響について検討した。推移パターンは高値持続型，増加型，変動型，減少型，低値安定型に分類した。罹病期間の長さにかかわらず，高値持続型，増加型，変動型での発症率は，低値安定型と比較し有意に高く，特に罹病期間が長期のものほど，高値を示した。また，治療内容にかかわらず，高値持続型，増加型，変動型で高い発症率を示したが，インスリン群では，低値安定型でも高い発症率を示した。以上から，特に罹病期間が長くインスリン未使用治療のものほどHbA_1c値を長期間低値に抑えることが，網膜症発症防止に重要であり，5年間のHbA_1c値の推移パターン分類は，NIDDM患者の網膜症発症率の予測に有用であることが示唆された。

A group of 187 patients with non-insulin-dependent diabetes mellitus was monitored for five years. All the patients were checked for hemoglobin A_1c level and diabetic retinopathy at least twice a year. Clinically detectable diabetic retinopathy was absent initially and was present in 83 patients after five years. The fluctuation pattern of HbA_1c was classified into 5 types: continuously high, gradually increasing, unstable, decreasing and lower and stable. The incidence of manifestation of retinopathy was significantly higher in continuously high, increasing and unstable types than in lower and stable type. This tendency was more pronounced in patients with duration of diabetes longer than 10 years. The incidence was high in lower and stable type also when the patients were treated by insulin. The findings show that the incidence of manifestation of retinopathy after 5 years is dependent on HbA_1c levels. Attempts to keep HbA_1c at a low and stabilized level seem to be essential in preventing diabetic retinopathy, particularly in patients with longterm diabetes and without insulin therapy.