Prevalence of Neutropenia in the U.S. Population: Age, Sex, Smoking Status, and Ethnic Differences

Prevalence of Neutropenia in the U.S. Population: Age, Sex, Smoking Status, and Ethnic Differences

From National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, and Social & Scientific Systems, Inc., Silver Spring, Maryland.

Abstract

Background: Benign reductions in neutrophil counts may be more common at certain ages and in certain ethnic groups and may be affected by sex and smoking status.

Objective: To determine differences in neutrophil counts in the U.S. population according to ethnicity, age, sex, and smoking status.

Design: Population-based, cross-sectional study.

Setting: Various locations in the United States.

Participants: 25 222 participants in the 1999 to 2004 National Health and Nutrition Examination Survey who were 1 year of age or older.

Measurements: Complete blood counts and comparison of means and the proportion of participants with neutropenia.

Results: Relative to white participants, black participants had lower leukocyte counts (mean difference, 0.89 × 10⁹ cells/L; P < 0.001), lower neutrophil counts (0.83 × 10⁹ cells/L; P < 0.001), and similar lymphocyte counts (0.022 × 10⁹ cells/L; P = 0.36), whereas Mexican-American participants had slightly higher mean leukocyte counts (0.16 × 10⁹ cells/L; P = 0.014), higher neutrophil counts (0.11 × 10⁹ cells/L; P = 0.026), and higher lymphocyte counts (0.095 × 10⁹ cells/L; P < 0.001). The prevalence of neutropenia (neutrophil count <1.5 × 10⁹ cells/L) was 4.5% among black participants, 0.79% among white participants, and 0.38% among Mexican-American participants. The prevalence of neutropenia was higher among males and children younger than 5 years of age. Neutrophil counts less than 1.0 × 10⁹ cells/L were observed in fewer than 1% of the overall sample (0.57% in black participants, 0.11% in white participants, and 0.08% in Mexican-American participants). Smoking was associated with higher leukocyte and neutrophil counts but had a smaller effect among black and Mexican-American participants than among white participants.

Limitation: Because estimates are based on single measures, fluctuations over time could not be determined.

Conclusions: In the United States, neutrophil counts are lower in black persons than in white persons and neutropenia is more prevalent in black persons. Neutrophil counts are slightly higher in Mexican-American persons than in white persons, and neutropenia is uncommon in both groups. The clinical implications of these findings are unclear, but they suggest that when determining the need for a diagnostic evaluation for neutropenia, clinicians should consider the patient's age, sex, ethnicity, and smoking status.

Article and Author Information

Acknowledgments: The authors thank Drs. Geraldine Schechter and Daniel Wright for their helpful comments and Keith Rust for statistical analyses.
Potential Financial Conflicts of Interest: None disclosed.
Grant Support: By the intramural research program of the National Institute of Diabetes and Digestive and Kidney Diseases at the National Institutes of Health.
Requests for Single Reprints: Griffin P. Rodgers, MD, Molecular and Clinical Hematology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, 9000 Rockville Pike, Building 10, 9N 119, Bethesda, MD 20892; e-mail, gr5n{at}nih.gov.
Current Author Addresses: Drs. Hsieh, Tisdale, and Rodgers: Molecular and Clinical Hematology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, 9000 Rockville Pike, Building 10, 9N 119, Bethesda, MD 20892.
Dr. Everhart: Epidemiology and Clinical Trials Branch, Division of Digestive Diseases and Nutrition, National Institute of Diabetes and Digestive and Kidney Diseases, 2 Democracy Plaza, Room 655, 6707 Democracy Boulevard, MSC 5450, Bethesda, MD 20892-5450.
Ms. Byrd-Holt: Computer Systems Data Analysis Division, Social & Scientific Systems, Inc., 8757 Georgia Avenue, 12th Floor, Silver Spring, MD 20910.
Author Contributions: Conception and design: M.M. Hsieh, J.E. Everhart, J.F. Tisdale, G.P. Rodgers.
Analysis and interpretation of the data: M.M. Hsieh, J.E. Everhart, D.D. Byrd-Holt, J.F. Tisdale.
Drafting of the article: M.M. Hsieh, J.E. Everhart, D.D. Byrd-Holt, J.F. Tisdale, G.P. Rodgers.
Critical revision of the article for important intellectual content: M.M. Hsieh, J.E. Everhart, J.F. Tisdale, G.P. Rodgers.
Final approval of the article: M.M. Hsieh, J.E. Everhart, D.D. Byrd-Holt, J.F. Tisdale, G.P. Rodgers.
Statistical expertise: J.E. Everhart, D.D. Byrd-Holt.