Platelet counts differ by sex, ethnicity, and age in the United States

PURPOSE: The aim of the study is to show that differences in platelet counts by ethnicity, sex, and age are not explained by environmental factors. METHODS: This is a cross-sectional population-based study of participants in the Third National Health and Nutrition Examination Survey. Our analytic sample included 12,142 participants, of whom 65% were women, 27% were non-Hispanic blacks, and 27% were Mexican Americans. We report weighted geometric mean platelet counts stratified by ethnicity, sex, and age and controlled for indicators of nutritional deficiencies and inflammation. RESULTS: The lowest mean platelet counts were in whites (260 x 10(3)/mu l; 95% confidence interval [CI], 256-264), and the highest were in non-Hispanic blacks (281 x 10(3)/mu L [95% CI, 276-286]). Older men and women of each ethnicity consistently had lower platelet counts than young adults; 60- to 69-year-olds had mean counts 7 x 10(3)/mu l lower (p < 0.001) and 70, to 90-year-olds had counts 18 x 10(3)/mu l lower (p < 0.001). Even controlling for iron deficiency, women had higher platelet counts than men (275 X 10(3)/mu L; 95% Cl, 271-279) versus 256 X 10(3)/mu L (95% Cl, 251-260; p < 0.001). CONCLUSIONS: Platelet count differences by sex, ethnicity, and age are not explained by environmental covariates known to influence platelet count.