title: Higher blood hematocrit predicts hypertension in men.
abstract: OBJECTIVE
  Little is known on the relationship between blood hematocrit level as an estimate of whole blood viscosity and the risk of hypertension. We investigated the relationship of higher hematocrit level with incident hypertension in men during a mean follow-up of 5 years.
  
  
  METHODS
  Participants were 3620 men (mean age 48 ± 6 years) who participated in two health examinations during 1998-2009. All participants were free of hypertension and within the normal range of hematocrit (39-50%) at baseline. The incidence of hypertension was defined as blood pressure values exceeding 140/90 mmHg of SBP and/or DBP at time of follow-up examination.
  
  
  RESULTS
  During 17,856 person-years of follow-up, 351 new cases of hypertension developed. The relative risk (RR) of incident hypertension in men with hematocrit in the highest tertile vs. men with hematocrit in the lowest tertile was 1.45 (95% confidence interval, CI 1.11-1.90) after adjustment for confounding factors. Every 1% increment in hematocrit was associated with 7% (RR 1.07, 95% CI 1.02-1.13) higher incidence of hypertension after adjusting for risk factors. Men whose hematocrit increased over time had a 25% increased risk of developing hypertension (RR 1.25, 95% CI 1.01-1.57) compared with men with decreased hematocrit after adjustment for risk factors.
  
  
  CONCLUSIONS
  These results demonstrate that higher hematocrit levels, even within the normal range, were associated with the incidence of hypertension independent of other risk factors in men.
authors.affiliation: aDepartment of Sport Science, University of Seoul, Seoul, South Korea bDepartment of Medicine, Institute of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio cDepartment of Internal Medicine, Lapland Central Hospital, Rovaniemi, Finland dDepartment of Exercise Science, Syracuse University, Syracuse, New York, USA eCollege of Nursing, Korea University fCenter for Health Promotion, Samsung Medical Center, Sungkyunkwan University School of Medicine gDivision of Cardiology, Cheil General Hospital, Kwandong University College of Medicine, Seoul, South Korea.
authors.forename: Sae Young
authors.initials: SY
authors.lastname: Jae
authors.forename: Sudhir
authors.initials: S
authors.lastname: Kurl
authors.forename: Jari A
authors.initials: JA
authors.lastname: Laukkanen
authors.forename: Kevin S
authors.initials: KS
authors.lastname: Heffernan
authors.forename: Jina
authors.initials: J
authors.lastname: Choo
authors.forename: Yoon-Ho
authors.initials: YH
authors.lastname: Choi
authors.forename: Jeong Bae
authors.initials: JB
authors.lastname: Park
mesh_terms: D000328:Adult; D001794:Blood Pressure; D005500:Follow-Up Studies; D006400:Hematocrit; D006801:Humans; D006973:Hypertension / Q000097:blood* / Q000453:epidemiology / Q000209:etiology*; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D056910:Republic of Korea / Q000453:epidemiology; D012307:Risk Factors