Hematocrit Predicts Long-Term Mortality in a Nonlinear and Sex-Specific Manner in Hypertensive Adults

Hematocrit has been inconsistently reported to be a risk marker of cardiovascular morbidity and mortality. The Glasgow Blood Pressure Clinic Study cohort included 10951 hypertensive patients, who had hematocrit measured at their initial clinic visit and followed for ⩽35 years. Cox proportional hazards models were used to estimate hazard ratios for all-cause, cardiovascular, ischemic heart disease, stroke, and noncardiovascular mortality. There were 3484 deaths over a follow-up period of 173245 person-years. Hematocrit was higher in men (median, 0.44; interquartile range, 0.42–0.47) than in women (median, 0.41; interquartile range, 0.38–0.43). The lowest risk for all-cause mortality was seen in quartile 2 for men (range, 0.421–0.440) and women (range, 0.381–0.400). Compared with quartile 2, the adjusted hazard ratios for quartiles 1, 3, and 4 were, respectively, 1.11 (range, 0.97–1.28), 1.19 (range, 1.04–1.37), and 1.22 (range, 1.06–1.39) in men and 1.17 (range, 1.01–1.36), 0.97 (range, 0.83–1.13), and 1.19 (range, 1.04–1.37) in women. Men showed a J-shaped pattern for cardiovascular mortality and a linear pattern for noncardiovascular mortality in cause-specific analysis, whereas in women a U-shaped pattern was observed for noncardiovascular mortality only. Higher baseline hematocrit was associated with higher on-treatment blood pressure during follow-up. Baseline hematocrit did not affect the time to reach target blood pressure. The increased risk of death attributed to higher hematocrit was seen in men and women irrespective of their achievement of target blood pressure, indicating that the risk is independent of the effect of hematocrit on blood pressure. Hypertensive patients with hematocrit levels outside of the sex-specific reference ranges identified in this study should be targeted for more aggressive blood pressure and cardiovascular risk reduction treatment.

[1]  C. Borchgrevink,et al.  The Role of Red Cells in Haemostasis: the Relation between Haematocrit, Bleeding Time and Platelet Adhesiveness , 1961, British journal of haematology.

[2]  A. C. Guyton,et al.  Effect of Hematocrit on Venous Return , 1961, Circulation research.

[3]  C. Forbes,et al.  Haematocrit in Patients Attending a Hypertension Clinic , 1985, Scottish medical journal.

[4]  S. Chien,et al.  Blood rheology in myocardial infarction and hypertension. , 1986, Biorheology.

[5]  Blood rheology and hyperviscosity syndromes. , 1987, Bailliere's clinical haematology.

[6]  G. Friday,et al.  Acute stroke, hematocrit, and blood pressure. , 1987, Stroke.

[7]  G. Lowe.  1 Blood rheology in vitro and in vivo , 1987 .

[8]  R. Simon,et al.  Flexible regression models with cubic splines. , 1989, Statistics in medicine.

[9]  M. Trevisan,et al.  Hematocrit, blood pressure, and hypertension. The Gubbio Population Study. , 1992, Hypertension.

[10]  H. Tunstall-Pedoe,et al.  Rheological determinants of blood pressure in a Scottish adult population , 1992, Journal of hypertension.

[11]  C. Mörlin,et al.  Blood viscosity and peripheral vascular resistance in patients with untreated essential hypertension , 1993, Journal of hypertension.

[12]  G D Lowe,et al.  The relationship between blood viscosity and blood pressure in a random sample of the population aged 55 to 74 years. , 1993, European heart journal.

[13]  W. Kannel,et al.  Hematocrit and the risk of cardiovascular disease--the Framingham study: a 34-year follow-up. , 1994, American heart journal.

[14]  I. Perry,et al.  Haematocrit, hypertension and risk of stroke. , 1995, Journal of internal medicine.

[15]  H. Meiselman,et al.  Mean red cell volume as a correlate of blood pressure. , 1996, Circulation.

[16]  V. Miller,et al.  Differential response in cell proliferation to beta estradiol in coronary arterial vascular smooth muscle cells obtained from mature female versus male animals. , 1996, Endocrinology.

[17]  R. Rosenson,et al.  Distribution of blood viscosity values and biochemical correlates in healthy adults. , 1994, Clinical chemistry.

[18]  A. Rumley,et al.  Blood viscosity and risk of cardiovascular events: the Edinburgh Artery Study , 1997, British journal of haematology.

[19]  Fröhlich,et al.  Effects of hormone replacement therapies on fibrinogen and plasma viscosity in postmenopausal women , 1998, British journal of haematology.

[20]  A. Levey,et al.  A More Accurate Method To Estimate Glomerular Filtration Rate from Serum Creatinine: A New Prediction Equation , 1999, Annals of Internal Medicine.

[21]  V. Miller,et al.  Gender-related differences in vascular smooth muscle cell proliferation: implications for prevention of arteriosclerosis , 1999, Lupus.

[22]  V. Miller.  Gender and vascular reactivity , 1999, Lupus.

[23]  A. Rumley,et al.  Blood Rheology, Cardiovascular Risk Factors, and Cardiovascular Disease: The West of Scotland Coronary Prevention Study , 2000, Thrombosis and Haemostasis.

[24]  G D Lowe,et al.  Haematocrit, viscosity, erythrocyte sedimentation rate: meta-analyses of prospective studies of coronary heart disease. , 2000, European heart journal.

[25]  J. Croft,et al.  Hematocrit and the risk of coronary heart disease mortality. , 2001, American heart journal.

[26]  M. Woodward,et al.  Does sticky blood predict a sticky end? Associations of blood viscosity, haematocrit and fibrinogen with mortality in the West of Scotland , 2003, British journal of haematology.

[27]  G. Lowe,et al.  Relative Value of Inflammatory, Hemostatic, and Rheological Factors for Incident Myocardial Infarction and Stroke: The Edinburgh Artery Study , 2007, Circulation.

[28]  S. Nikkari,et al.  Hematocrit and the risk of coronary heart disease mortality in the TAMRISK study, a 28-year follow-up. , 2009, Preventive medicine.

[29]  P. Cabrales,et al.  The variability of blood pressure due to small changes of hematocrit. , 2010, American journal of physiology. Heart and circulatory physiology.