Elderly people with the lowest and highest hemoglobin concentrations are at increased risk of death

Elderly people with the lowest and highest hemoglobin concentrations (the component of red blood cells that carries oxygen) are at increased risk of death, according to a study in the October 24 issue of Archives of Internal Medicine.

Increasing evidence indicates that anemia is common in the elderly population, but few studies have assessed the association of anemia with clinical outcomes, such as illness and death, according to background information in the article. Anemia is defined by the World Health Organization (WHO) as a hemoglobin concentration of less than 12 g/dL (grams per one tenth liter) for women and less than 13 g/dL for men.

Neil A. Zakai, M.D., of the University of Vermont College of Medicine, Burlington, compared the association of hemoglobin concentration and anemia status with subsequent death over the course of eleven years in elderly adults living in four U.S. communities. Hemoglobin concentrations were determined for participants recruited between 1989 and 1993. Participants were contacted biannually; telephone and clinic examinations were conducted alternately. Deaths were reviewed and classified as cardiovascular or noncardiovascular. Complete follow-up was available through June 2001 for this analysis.

Hemoglobin concentration was analyzed in two ways: by dividing the participants' baseline hemoglobin into five equal levels and by the WHO criteria for anemia. Based on the WHO criteria for anemia, 498 individuals were anemic on enrollment (8.5 percent of the 5,797 included in the analysis), the researchers report. The hemoglobin concentration for the 1,205 individuals in the lowest fifth was higher than the WHO criteria for anemia, and 41.3 percent of these 1,205 people did qualify as anemic by WHO standards.

"In this elderly cohort, the prevalence of anemia was 7.0 percent among white and 17.6 percent among black individuals," the authors write. "After 11.2 years of follow-up, lower hemoglobin concentrations were associated with increased mortality risk, independent of many potentially confounding factors. The magnitude of this association was similar whether the lowest quintile [fifth] of hemoglobin or the WHO criteria for anemia was used; however, the number of participants was much larger when considering the lowest quintile of hemoglobin concentration." Another finding of the study was that there was also elevated mortality among those in the highest hemoglobin quintile, even after extensive adjustment for other factors.

"In conclusion, a lower hemoglobin concentration was independently associated with mortality in this elderly cohort," the authors write. "The bottom hemoglobin quintile defined a larger group at risk than anemia status based on WHO criteria. Future areas of investigation should determine the optimal hemoglobin value that defines an abnormal concentration in elderly individuals, study the causes of low hemoglobin concentrations in elderly individuals and how these relate differentially to outcomes, evaluate the causes of increased mortality in individuals with low and high hemoglobin concentrations, and assess whether treatment of low hemoglobin in the general population reduces mortality."