Impaired reduction of nocturnal systolic blood pressure and severity of diabetic retinopathy.

The aim of the present study was to evaluate the influence of elevated levels of nocturnal blood pressure (BP) on diabetic retinopathy (DR). A total of 88 diabetic hypertensive patients were divided according to the stage of DR. They underwent 24 h ambulatory BP monitoring and ophthalmological evaluation, and their average level of fasting blood glucose as well as their glycemic control index (percentage of fasting blood glucose higher than 11.2 mmol/L over the previous four years) were calculated. When diabetic patients with retinopathy (n=29) (group 1) were compared with patients without retinopathy (n=59) (group 2), a significant difference was observed in diabetes duration (124 months [range six to 460 months] versus 43 months [range six to 365 months], respectively; P<0.05). In addition, group 1 showed higher levels of nocturnal systolic BP (NSBP) (141 +/- 22 mmHg versus 132+/-18 mmHg; P<0.05). However, no significant differences were found between the two groups (group 1 and group 2) when diurnal pressoric levels were compared (diurnal systolic BP, 153+/-19 mmHg versus 146+/-19 mmHg, P not significant; and diurnal diastolic BP, 91+/-9 mmHg versus 91+/-13 mmHg, P not significant). DR correlated with diabetes duration (r=0.26; P<0.05) and with glycemic control index (r=0.24; P<0.01). Multivariate regression analysis showed NSBP to be an independent predictor of DR (r(2)=0.12; P<0.01). Moreover, patients with severe stages of DR (preproliferative, proliferative or macular edema) showed a lower decrease of NSBP than the other patients (3.9+/-6.0 mmHg versus 9.2+/-6.0 mmHg; P<0.05). The present study suggests that the absence of 24 h normal pressoric rhythm can interfere with the prevalence and severity of DR.