Total and differential white blood cell counts and their associations with circulating interleukin-6 levels in community-dwelling older women.
BACKGROUND
Interleukin-6 (IL-6) is an inflammatory biomediator, and age-related increases in IL-6 levels are associated with osteoporosis, sarcopenia, disability, and mortality in older adults. Although white blood cells (WBC), or leukocytes, are known to produce IL-6 in vitro, their in vivo relationship with circulating IL-6 levels is not well established.


METHODS
In this cross-sectional analysis of data from the Women's Health and Aging Study I, the authors evaluated the relationships of total WBC and WBC differential (neutrophil, monocyte, lymphocyte, eosinophil, and basophil) counts to circulating IL-6 levels in 619 community-dwelling older women. Potential associations of age, race, and cigarette smoking with total and differential WBC counts and IL-6 levels were also assessed.


RESULTS
Except for lymphocyte and basophil counts, significant associations of total WBC, neutrophil, monocyte, and eosinophil counts with IL-6 levels were identified. These associations remained highly significant after adjustment for age, race, and smoking status. Total WBC, neutrophil, monocyte, and eosinophil counts had significant stepwise increases in four escalating quartiles of IL-6 levels. In addition, age, race, and cigarette smoking were differentially associated with total and differential WBC counts and IL-6 levels.


CONCLUSIONS
Positive in vivo associations of total WBC and its specific subpopulations were identified, including neutrophils, monocytes, and eosinophils, with circulating IL-6 levels in community-dwelling older women. These findings suggest significant contributions of WBC and its subpopulations to circulating IL-6 levels and potential effects from chronic elevation of IL-6 levels to the function of these circulating immune cells that warrant further investigation.
Leng
Sean
S
Division of Geriatric Medicine and Gerentology, Johns Hopkins Asthma and Allergy Center, Room 5A.24, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA.
Xue
Qian-Li
QL
Huang
Yi
Y
Semba
Richard
R
Chaves
Paulo
P
Bandeen-Roche
Karen
K
Fried
Linda
L
Walston
Jeremy
J
D000367:Age Factors; D000368:Aged / Q000502:physiology*; D003430:Cross-Sectional Studies; D004804:Eosinophils; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D007958:Leukocyte Count; D018655:Lymphocyte Count; D009000:Monocytes; D009504:Neutrophils; D044469:Racial Groups; D012907:Smoking / Q000097:blood
D015850:Interleukin-6