Combined effect of diabetic retinopathy and diabetic kidney disease on all‐cause, cancer, vascular and non‐cancer non‐vascular mortality in patients with type 2 diabetes: A real‐world longitudinal study

AIMS/INTRODUCTION: We assessed the relationship between diabetic retinopathy (DR) and/or diabetic kidney disease (DKD) according to their severity and all‐cause, cancer, vascular and non‐cancer non‐vascular mortality in real‐world patients with type 2 diabetes. MATERIALS AND METHODS: A total of 1,902 patients with type 2 diabetes were enrolled from 1995 to 1999 and followed to 2017. At baseline, DR was diagnosed in 374 patients, DKD in 529, vision‐threatening DR in 123 and advanced DKD in 287. Patients were classified by the status of DR and DKD. Multivariate Cox regression analysis was carried out. RESULTS: There were 266 deaths during a median follow‐up period of 18.6 years. Among these, 92 were from cancer, 78 were from vascular causes and 82 were from non‐cancer non‐vascular causes. DR and/or DKD predicted all‐cause, vascular and non‐cancer non‐vascular mortality, but not cancer mortality. Similarly, vision‐threatening DR and/or advanced DKD predicted all‐cause, vascular and non‐cancer non‐vascular mortality, but not cancer mortality. Hazard ratios for all‐cause, vascular and non‐cancer non‐vascular mortality were highest in the DR(+)DKD(+) group, and higher in the DR(−)DKD(+) and the DR(+)DKD(−) groups than in the DR(−)DKD(−) group. The results for vision‐threatening DR and advanced DKD were similar. The interaction for non‐cancer non‐vascular mortality, but not all‐cause and vascular mortality, between DR and DKD and between vision‐threatening DR and advanced DKD might be significant. CONCLUSIONS: DR and DKD may be jointly and independently associated with all‐cause, vascular and non‐cancer non‐vascular mortality, but not cancer mortality, according to their severity in real‐world patients with type 2 diabetes.