Diabetes, Vol 45, Issue 5 576-579, Copyright © 1996 by American Diabetes Association
Hematocrit and risk of NIDDM
SG Wannamethee, IJ Perry and AG Shaper
Department of Public Health, The Royal Free Hospital School of Medicine, London, U.K.
There is limited evidence that raised hematocrit levels may be associated
with insulin resistance, which links cardiovascular disease with NIDDM. The
association between hematocrit level at screening and the subsequent
development of physician-diagnosed NIDDM during 12.8 years of follow-up was
examined in a prospective study of 7,735 middle-aged men drawn at random
from general practice in 24 British towns. With the exclusion of men with
missing hematocrit data and men with diabetes at screening, data were
available for 7,193 men, in whom there were 187 new cases of NIDDM during
follow-up. The risk of NIDDM increased significantly with increasing
hematocrit levels. There was more than a fourfold increase in relative risk
(RR) of diabetes among men with a hematocrit of > or = 48% relative to
those with a hematocrit <42%, adjusted for age and BMI (RR 4.5; 95% CI
2.5-6.3). On further adjustment for predictors of NIDDM with which
hematocrit is correlated, there remained a strong linear association with
the risk of diabetes. There was a nearly fourfold increased risk of NIDDM
in the highest relative to the lowest hematocrit group in the fully
adjusted proportional hazard model (RR 3.6; 95% CI 1.7-7.6). The strong
positive association between hematocrit level and risk of diabetes was seen
even after exclusion of men with preexisting ischemic heart disease. The
findings suggest that a raised hematocrit level, which is a major
determinant of whole blood viscosity, should be added to the cluster of
risk factors that link NIDDM with atheromatous, vascular disease.