Haematocrit: a predictor of cardiovascular mortality ?

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Abstract
Objectives. The main purpose of the study was to assess a possible association between haematocrit (Hct) and long‐term cardiovascular disease (CVD) mortality.Design. An extensive examination programme was carried out in 2014 men, defined as apparently healthy, during the period 1972 to 1975, including Hct measurements in a 25% random subsample. Sequential, cause‐specific mortality was followed prospectively over a period of 16 years.Setting. The survey was conducted at Medical Department B, Rikshospitalet, Oslo, Norway.Subjects. The participants represented 86% of all eligible apparently healthy men working in five preselected companies in Oslo.Interventions. No intervention was given by the study group during follow‐up.Main outcome measures. Complete, cause‐specific mortality figures after 8–16 years were obtained from the Norwegian Central Bureau of Statistics.Results. Hct measures were obtained in 488 men (24.2%). Mean Hct was 47.2% (sd 2.9%). After correcting for differences in age, plasma cholesterol, systolic blood pressure, erythrocyte sedimentation rate and smoking habits (Cox proportional hazards model), an increase in Hct by 2 SDS was associated with an increase in CVD mortality by a factor ranging between 2.9 at 10, and 1.9 at 16 years (P < 0.05). A similar increased risk was observed earlier during follow‐up but the number of deaths was too small for meaningful statistical analysis. No association was found between Hct and non‐CVD mortality.Conclusions. Our data show that increased Hct is associated with an increased risk of dying from CVD—independent of conventional CVD risk factors.