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Hematocrit and the risk of coronary heart disease mortality
D W Brown1, W H Giles, J B Croft
1Cardiovascular Health Branch, Division of Adult and Community Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta, GA 30341-3717, USA.
Insights
Hematocrit (Hct) levels show a complex association with coronary heart disease (CHD) mortality, varying significantly by sex and age. High Hct is linked to increased CHD mortality in women, particularly younger ones, but not in men.
Area of Science:
- Cardiovascular epidemiology
- Hematology
- Public health
Background:
- Previous observations suggest a link between hematocrit (Hct) and coronary heart disease (CHD) mortality.
- The relationship between Hct and CHD, independent of other cardiovascular disease (CVD) risk factors, and sex-specific differences remain unclear.
Purpose of the Study:
- To investigate the association between hematocrit (Hct) and coronary heart disease (CHD) mortality.
- To examine sex-specific differences in the Hct-CHD mortality relationship, adjusting for various CVD risk factors.
Main Methods:
- Cox regression analyses were performed on data from 8896 adults (aged 30-75) in the NHANES II Mortality Study (1976-1992).
- Hematocrit (Hct) was categorized into sex-specific tertiles.
- Analyses were stratified by sex and adjusted for covariates including age, race, smoking, hypertension, cholesterol, BMI, white blood cell count, and history of CVD and diabetes.
Main Results:
- After multivariate adjustment, no association was found between high Hct and CHD, heart disease, or all-cause mortality in men.
- Women with high Hct showed a 1.3-fold increased likelihood of CHD mortality compared to those with low Hct.
- The association between high Hct and CHD mortality was stronger in women under 65 years (RR 2.2).
Conclusions:
- The association between hematocrit (Hct) and mortality from CHD and all causes is complex and differs by sex and age.
- Further research is warranted to elucidate these age and sex-specific differences in the Hct-CHD mortality relationship.
Background:
An association between hematocrit (Hct) and coronary heart disease (CHD) mortality has been previously observed. However, the relationship of Hct and CHD independent of other cardiovascular disease (CVD) risk factors and differences between men and women remain unclear.
Methods:
We examined the association between Hct and CHD mortality with Cox regression analyses of data from 8896 adults, aged 30-75 years, in the Second National Health and Nutrition Examination Survey (NHANES II) Mortality Study (1976-1992). Covariates included age, sex, race, education, smoking status, hypertensive status, total serum cholesterol, body mass index, white blood cell count, and history of CVD and diabetes. Hct was categorized by use of sex-specific tertiles, and all analyses were stratified by sex.
Results:
During 16.8 years of follow-up, there were 545 (men 343, women 202) deaths from CHD (International Classification of Diseases, 9th revision [ICD-9] 410-414), 778 (men 426, women 279) deaths from diseases of the heart (ICD-9 390-398, 402, 404, 410-414, 415-417, 420-429), and 2046 (men 1216, women 830) all-cause deaths. Among men, the crude CHD mortality rate per 10,000 population was 42.6, 31.9, and 46.3 among those with Hct in the lower, middle, and upper tertiles, respectively. The corresponding crude CHD mortality rates among women were 12.6, 18.6, and 27.7. After adjustment for age and other CVD risk factors, there was no association between Hct in the upper tertile compared with the lower tertile and mortality from either CHD, diseases of the heart, or all causes among men. Women with Hct in the upper tertile were 1.3 times (95% CI 0.9-1.9) more likely to die from CHD than were women with Hct in the lowest tertile, after multivariate adjustment. The effect of high Hct on CHD mortality among women younger than 65 years of age was slightly stronger (relative risk 2.2, 95% CI 1.0-4.6).
Conclusions:
These results suggest that the association between Hct and mortality from CHD and all causes is complex, differing both by sex and age. Further research is needed to gain a better understanding of these age and sex differences.