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Leucocyte count may predict heart disease in women

Calgary Barbara Kermode-Scott

A new study indicates that a white blood cell count is an independent predictor of cardiovascular events and of mortality from all causes in postmenopausal women.

The research, published in the Archives of Internal Medicine (2005;165:500-8), showed that a leucocyte count greater than 6.7 x 109/l may identify postmenopausal women at high risk of disease who are not currently identified by traditional cardiovascular risk factors.

Doctors should pay attention to white blood cell counts in the upper normal range in postmenopausal women, said the principal investigator, Karen Margolis, an associate professor of medicine at the University of Minnesota.

Dr Margolis and her colleagues studied how leucocyte counts predicted cardiovascular events among 72 242 postmenopausal women aged 50 to 79 years who participated in the US women’s health initiative observational study. At baseline the women were free of cardiovascular disease and cancer. The main outcome measures included fatal coronary heart disease, non-fatal myocardial infarction, stroke, and total mortality.

The researchers divided the women into four groups according to their initial white blood cell counts. During a mean of 6.1 years of follow up there were 187 deaths from coronary heart disease, 701 non-fatal myocardial infarctions, 738 strokes, and 1919 deaths from all causes.

The risk of death from coronary heart disease among women in the group with the highest leucocyte counts (from 6.7 x 109 cells/l to 15 x 109cells/l) was more than twice that among women in the lowest group (2.5 109 cells/l to 4.7 x109 cells/l), after adjustment for other risk factors (hazard ratio, 2.36, 95% confidence interval, 1.51 to 3.68). These included age, race, diabetes, hypertension, smoking, hypercholesterolaemia, body mass index, alcohol intake, diet, physical activity, use of aspirin, and use of hormone treatments. Women in the highest group also had a 40% higher risk of non-fatal myocardial infarction (hazard ratio 1.41 (95% confidence interval, 1.12 to 1.78)), a 46% higher risk of stroke (1.46 (1.17 to 1.81)), and a 50% higher risk of total mortality (1.52 (1.33 to 1.74)) than women in the lowest group, after adjustment for potential confounders.

“We can mostly account for cardiovascular disease by the known risk factors, such as hypertension, hypercholesterolaemia, smoking, diabetes, age, and overweight,” said Dr Margolis. “So any new biomarker is only going to add a little to our knowledge. But the white blood cell count adds something and works just as well as other inflammatory biomarkers that have received a lot of publicity lately, such as the C reactive protein.”

This is the first study in healthy individuals of either sex in which the C reactive protein concentration and the white blood cell count were compared head to head, she added. “In multivariable models adjusting for C reactive protein, the total leucocyte count was an independent predictor of coronary heart disease risk, comparable in magnitude to C reactive protein.

“The white blood cell count comes out at least as strong a predictor of coronary heart disease as the C reactive protein,” said Dr Margolis. “In any situation in which you might consider testing C reactive protein to further evaluate cardiovascular risk, then the white blood cell count could be considered as an alternative.”