White blood cell count, coronary heart disease, and death: The NHANES I Epidemiologic Follow-up Study

Abstract

To confirm the reported association of elevated WBC count with increased risk of CHD incidence and death in white men and to determine whether such associations exist for CHD incidence and death in women and blacks, data were examined from the NHANES I Epidemiologic Follow-up Study. Over a follow-up period of 7 to 16 years, WBC counts >8100 cells/mm3 compared with WBC counts <6600 cells/mm3 were associated with increased risk of CHD incidence in white men (RR = 1.31; 95% CL 1.07, 1.61) and in white women (RR = 1.31; 1.05, 1.63) aged 45 to 74 after adjustment for baseline risk factors. The association was found in white female but not in white male subjects who had never smoked. Increases in risk of death from all causes, cardiovascular diseases, and noncardiovascular diseases were also seen in all white men in the sample. RRs for death for all causes at ages 45 to 74, which compared the upper and lower strata of WBC counts, were 1.43 (95% CL 1.22, 1.68) in all white men and 1.33 (95% CL 1.00, 1.78) in subjects who had never smoked after adjustment for baseline risk factors. Similar increases in risk of death from all causes were seen in blacks aged 45 to 64 despite small sample size. Thus this analysis failed to clearly establish an increased risk of CHD incidence in white men with relatively elevated WBC counts who never smoked cigarettes, although such an association was evident in white women. The increased risk of death from all causes in men appeared to be only partially due to effects of smoking. The lack of clear-cut effects of elevated WBC counts on risk of death in white women is unexplained. Further studies are needed to quantify effects of elevated WBC counts in nonsmoking men, women, and blacks and to elucidate mechanisms for the effect of a relatively elevated WBC count on mortality and morbidity rates.