G Wannamethee1, I J Perry, A G Shaper. 1. Department of Public Health and Primary Care, Royal Free Hospital School of Medicine, London, UK.
Abstract
OBJECTIVES: To assess the relationship between haematocrit and risk of stroke. DESIGN: Prospective study of a cohort of men followed up for 9.5 years. SETTING: General practices in 24 towns in England, Scotland and Wales (British Regional Heart Study). SUBJECTS: A total of 7735 men aged 40-59 years at screening, selected at random from one general practice in each of 24 towns. MAIN OUTCOME MEASURES: Fatal and non-fatal strokes. RESULTS: During a follow-up period of 9.5 years for all men there were 123 stroke events (33 fatal) in the 7346 men in whom the haematocrit level had been determined. In the cohort as a whole, risk of stroke was significantly raised at haematocrit levels > or = 51% (relative risk [RR] = 2.5; 95% confidence intervals [CI] 1.2-5.0) after adjustment for age, social class, smoking, body mass index, physical activity, presence of diabetes and pre-existing ischaemic heart disease. Further adjustment for systolic blood pressure did not attenuate this association (RR = 2.4; 95% CI 1.2-4.9). A raised haematocrit was associated with an increase of stroke only in men with hypertension (systolic blood pressure > or = 160 mmHg or diastolic blood pressure > or = 90 mmHg or on regular antihypertensive treatment). No increased risk of stroke was seen at the higher haematocrit level (> or = 51%) in normotensive men. At haematocrit levels below 51%, hypertension was associated with a three-fold increase in risk of stroke compared with normotension (RR = 3.4, 95% CI 2.3, 5.1). At haematocrit levels > or = 51%, hypertension was associated with a nine-fold increase in risk of stroke compared with normotension (RR = 9.3; 95% CI 4.2, 21.0). Exclusion of men receiving regular antihypertensive therapy did not alter the strong associations seen. CONCLUSION: The data suggest that an elevated haematocrit is an independent risk factor for stroke and that it interacts synergistically with elevated blood pressure.
OBJECTIVES: To assess the relationship between haematocrit and risk of stroke. DESIGN: Prospective study of a cohort of men followed up for 9.5 years. SETTING: General practices in 24 towns in England, Scotland and Wales (British Regional Heart Study). SUBJECTS: A total of 7735 men aged 40-59 years at screening, selected at random from one general practice in each of 24 towns. MAIN OUTCOME MEASURES: Fatal and non-fatal strokes. RESULTS: During a follow-up period of 9.5 years for all men there were 123 stroke events (33 fatal) in the 7346 men in whom the haematocrit level had been determined. In the cohort as a whole, risk of stroke was significantly raised at haematocrit levels > or = 51% (relative risk [RR] = 2.5; 95% confidence intervals [CI] 1.2-5.0) after adjustment for age, social class, smoking, body mass index, physical activity, presence of diabetes and pre-existing ischaemic heart disease. Further adjustment for systolic blood pressure did not attenuate this association (RR = 2.4; 95% CI 1.2-4.9). A raised haematocrit was associated with an increase of stroke only in men with hypertension (systolic blood pressure > or = 160 mmHg or diastolic blood pressure > or = 90 mmHg or on regular antihypertensive treatment). No increased risk of stroke was seen at the higher haematocrit level (> or = 51%) in normotensive men. At haematocrit levels below 51%, hypertension was associated with a three-fold increase in risk of stroke compared with normotension (RR = 3.4, 95% CI 2.3, 5.1). At haematocrit levels > or = 51%, hypertension was associated with a nine-fold increase in risk of stroke compared with normotension (RR = 9.3; 95% CI 4.2, 21.0). Exclusion of men receiving regular antihypertensive therapy did not alter the strong associations seen. CONCLUSION: The data suggest that an elevated haematocrit is an independent risk factor for stroke and that it interacts synergistically with elevated blood pressure.
Authors: Malin Hultcrantz; Anton Modlitba; Senthil K Vasan; Arvid Sjölander; Klaus Rostgaard; Ola Landgren; Henrik Hjalgrim; Henrik Ullum; Christian Erikstrup; Sigurdur Y Kristinsson; Gustaf Edgren Journal: Thromb Res Date: 2019-12-20 Impact factor: 3.944
Authors: Vincent Richter; Michele D Savery; Max Gassmann; Oliver Baum; Edward R Damiano; Axel R Pries Journal: J Physiol Date: 2011-08-22 Impact factor: 5.182