LONGITUDINAL RELATION BETWEEN SMOKING AND WHITE BLOOD-CELLS

Higher white blood cell counts in smokers compared with nonsmokers hav e been well documented, but the longitudinal relation between changes in smoking and changes in white blood cells has not been well describe d. Since 1984, data have been collected semiannually by the Multicente r AIDS Cohort Study (MACS), a four-center prospective cohort study of acquired immunodeficiency syndrome (AIDS) in homosexual men. The study population includes 2,435 participants who were human immunodeficienc y virus (HIV) seronegative as of Sept ember 1994 and who contributed 2 0,918 person-visits for this analysis, For individuals who modified th eir smoking behavior, changes in white blood cell counts occurred prim arily during the first 6 months following changes in the amount of cig arettes smoked. Among former smokers who resumed smoking, the extent o f the increase in white blood cell count depended on the number of cig arettes smoked. Specifically, increases of 241, 340, and 740 cells/mu liter were observed for smokers who resumed smoking (1, 1 to <2, and g reater than or equal to 2 paeks/day, respectively. Conversely, smokers who quit smoking had a decrease of white blood cell count: -32, -629, and -1,122 cells/mu liter for men who previously smoked <1, 1 to <2, a nd greater than or equal to 2 packs/day, respectively. Long-term ex-sm okers, however, still had higher white blood cell counts than did neve r smokers, There was a high within-individual correlation of white blo od cell count in persons who reported a consistent level of smoking (i .e., average correlations between two white blood cell counts 6 years apart were 0.51 for never smokers, 0.48 for ex-smokers, 0.56 for men w ho smoked <1 pack/day, and 0.43 for men who smoked greater than or equ al to 1 pack/day). These analyses indicate an acute effect of changes in smoking on changes in white blood cell count, a residual effect of having been a smoker, and high long-term tracking for white blood cell count.