Risk factors for nephropathy in persons with type 1 diabetes: a population-based study.

Aims: Albuminuria is strongly associated with risk of renal dysfunction, cardiovascular disease and mortality. However, clinical guidelines diverge, and evidence is sparse on what risk factor levels regarding blood pressure, blood lipids and BMI are needed to prevent albuminuria in adolescents and young adults with type 1 diabetes.

Methods: A total of 9347 children and adults with type 1 diabetes [mean age 15.3 years and mean diabetes duration 1.4 years at start of follow-up] from The Swedish National Diabetes Registry were followed from first registration until end of 2017. Levels for risk factors for a risk increase in nephropathy were evaluated, and the gradient of risk per 1 SD (standard deviation) was estimated to compare the impact of each risk factor.

Results: During the follow-up period, 8610 (92.1%) remained normoalbuminuric, 737 (7.9%) individuals developed micro- or macroalbuminuria at any time period of whom 132 (17.9% of 737) individuals developed macroalbuminuria. Blood pressure ≥ 140/80 mmHg was associated with increased risk of albuminuria (p ≤ 0.0001), as were triglycerides ≥ 1.0 mmol/L (p = 0.039), total cholesterol ≥ 5.0 mmol/L (p =  0.0003), HDL < 1.0 mmol/L (p = 0.013), LDL 3.5- < 4.0 mmol/L (p = 0.020), and BMI ≥ 30 kg/m (p =  0.033). HbA1c was the strongest risk factor for any albuminuria estimated by the measure gradient of risk per 1 SD, followed by diastolic blood pressure, triglycerides, systolic blood pressure, cholesterol and LDL. In patients with HbA1c > 65 mmol/mol (> 8.1%), blood pressure > 140/70 mmHg was associated with increased risk of albuminuria.

Conclusions: Preventing renal complications in adolescents and young adults with type 1 diabetes need avoidance at relatively high levels of blood pressure, blood lipids and BMI, whereas very tight control is not associated with further risk reduction. For patients with long-term poor glycaemic control, stricter blood pressure control is advocated.