Phenotyping normal kidney function in elderly patients with type 2 diabetes: a cross-sectional multicentre study

G P Fadini, A Solini, M L Manca, G Zatti, I Karamouzis, A Di Benedetto, L Frittitta, A Avogaro, For the DARWIN-T2D Network

Type 2 diabetes (T2D) accelerates the decline in glomerular function; however, some individuals do not develop chronic kidney disease despite advanced age and long-lasting T2D. We aimed to phenotype patients with T2D aged 80 years or older who presented with a fully preserved kidney function. From an Italian population of 281,217 T2D outpatients, we collected data on demographics, anthropometrics, diabetes duration, HbA1c, fasting plasma glucose, lipids, liver enzymes, estimated glomerular filtration rate (eGFR), albumin excretion rate (AER), chronic complications, and medication use. We primarily compared patients with a fully preserved kidney function (eGFR > 90 ml/min/1.73 m2 and AER < 30 mg/24 h, or G1A1) with those with mild kidney impairment (eGFR 60-90 ml/min/1.73 m2 and AER < 30 mg/24 h, or G2A1). N = 113,860 had available data for eGFR and AER, 21,648 of whom were aged ≥ 80. G1A1 (n = 278) and G2A1 (n = 6647) patients represented 1.3 and 30.7% of aged T2D patients, respectively, with an average diabetes duration of 16 years. Differences between the G1A1 and G2A1 groups were entered in a multiple logistic regression analysis with and without imputation of missing data. After adjustment and in both imputed and non-imputed datasets, younger age, lower BMI and lower triglycerides were associated with fully preserved versus mildly impaired kidney function. The comparison between G1A1 and G1A2/3 yielded different results. In a rare population of patients with a fully preserved kidney function despite old age and long-lasting diabetes, lower BMI and triglycerides suggest that protection from lipotoxicity may preserve kidney function over time.