Age-related change in relationship between white blood cell count and some features of the metabolic syndrome.

To examine age-related change in the strength of the association of white blood cell count (WBC) with features of the metabolic syndrome (MS), body mass index, blood pressure, total cholesterol, high-density lipoprotein (HDL) cholesterol, triglycerides, fasting plasma glucose, and uric acid were assessed as the components of the MS in 5,218 Japanese male office workers aged 23-59 yr. The subjects were stratified by age into three groups of 23-39, 40-49, and 50-59 yr. WBC count showed a positive crude correlation with the components of the MS, except for HDL cholesterol (negative), in all three age groups. With an increase in age, an association between WBC count and each component of the MS declined, and an interaction with age weakened. After controlling for potential confounders, the largest differences of WBC count for each categorized feature of the MS were found among those aged 23-39 yr. Stratified analyses by smoking status and age showed that in both non-smokers and current smokers the adjusted WBC count increased as the number of features of the MS increased in all three age groups. In each category of the number of clustered features of the MS, differences of WBC count compared with the presence of no features of the MS were the largest in those aged 23-39 yr in both non-smokers and current smokers. The adjusted odds ratios of > or =3 features of the MS also increased with an increase in WBC count in all three age groups in both non-smokers and current smokers. The adjusted odds ratios of > or =3 features of the MS across quartiles of WBC count (lowest to highest) were the largest in the youngest age group. Our results indicate that a variety of features of the MS are associated with WBC count and that these tendencies are more pronounced in younger individuals in both non-smokers and current smokers.