Higher White Blood Cell Count May Boost Death Risk

An analysis of death records revealed that those participants who died during the study period had higher WBC counts than those who survived through to 2002.

The finding applied to all patients regardless of their initial baseline WBC count, and held regardless of gender, age at death, or year of death. However, women tended to have significantly lower WBC levels than men.

Patients who had WBC counts between 3,500 and 6,000 cells per microliter of blood had the lowest observed rate of death, while those with readings above 10,000 had the highest death rate.

No firm conclusions were drawn regarding the risk for patients with WBC levels below 3,500.

However, the authors observed that death risk varied even within the normal WBC count range. Those with a high-normal WBC count of 6,000 to 10,000 had a 30 percent to 40 percent higher risk of death than patients with a low-normal WBC count of 3,500 to 6,000, the researchers said.

Ruggiero's team also calculated that for every additional 1,000 cells above the lowest end of the normal range (3,500), a patient's risk of death rose by just over 10 percent.

WBC counts, especially for a type of cell called neutrophils, rose progressively in the years before death, with significant bumps upward observed as early as five years prior to the end of a patient's life. In contrast, WBC counts remained relatively stable among people who survived.

People who died were also more likely to have smoked, to have been less physically active, and to have had worse cardiovascular health.

Death as a result of cardiovascular disease, especially, rose along with increasing WBC counts. WBC counts showed little connection to deaths by cancer.

Overall, white blood cell counts fell for both men and women over the nearly 45-year study period. A host of societal and lifestyle changes could explain the drop, the researchers said, including improvements in diet and exercise habits and the steady drop in smoking and drinking. Environmental changes, such as improved sanitary conditions and less frequent exposure to infectious agents, could also be factors.

The death rate for Americans has also fallen steadily over the past four decades, the authors noted. However, they stressed that they cannot establish any causal link between declines in white blood cell counts and improving life expectancy.

Measuring WBC might prove useful in predicting an individual's health risk, however.