Blood viscosity in young male diabetics with and without retinopathy.

Blood viscosity (shear rates 100s-1 and 0.94s-1) and several of its major determinants (haematocrit, plasma fibrinogen and plasma viscosity) have been measured in 38 male insulin-treated diabetics, aged 18-50 years, and in 38 non-diabetic control subjects matched for age and smoking habit. Diabetics without fundoscopic retinopathy (n=20) had higher mean blood viscosity than controls at the high shear rate (7.07 cP vs 6.75 cP, p < 0.05) and the low shear rate (21.2 cP vs 18.7 cP, p < 0.025). These differences persisted after correction of blood viscosity to a standard haematocrit, and were associated with increased plasma viscosity (1.41 cP vs 1.34 cP, p < 0.025) and plasma fibrinogen (2.9 g/L vs. 2.5 g/L, p < 0.025). Diabetics with retinopathy (n = 18) had higher mean blood viscosity than diabetics without retinopathy at the high shear rate (7.53 cP vs 7.07 cP, p < 0.05) and the low shear rate (24.3 cP vs. 21.2 cP, p < 0.05), associated with a higher haematocrit (p < 0.05). Blood viscosity and haematocrit correlated with the duration of diabetes (r > 0.32, p < 0.05).