Objectives: To evaluate relationships between white blood cell (WBC) count and interleukin-6 (IL-6) and prevalent frailty.
Design: Cross-sectional study.
Setting: Two population-based studies, the Women's Health and Aging Studies (WHAS) I and II, Baltimore, Maryland.
Participants: Five hundred fifty-eight women aged 65 to 101 from WHAS I and 548 women aged 70 to 79 from the merged WHAS I and II cohorts.
Measurements: Frailty was determined using validated screening criteria. WBC counts and IL-6 levels were measured using standard laboratory methods. Odds ratios (ORs) for frailty were evaluated across tertiles of baseline WBC counts and IL-6 levels, adjusting for age, race, education, body mass index, and smoking status.
Results: In WHAS I, those in the top tertile of WBC count and IL-6 had ORs of 4.25 (95% confidence interval (CI)=1.89-9.58) and 3.98 (95% CI=1.76-9.00), respectively, for frailty (both P<.001). In the combined models, participants in the top tertile of WBC count had an OR of 3.15 (95% CI=1.34-7.41), adjusting for IL-6 (P<.01), and those in the top tertile of IL-6 had an OR of 2.81 (95% CI=1.19-6.64), adjusting for WBC count (P<.05). Furthermore, participants in the top tertiles of WBC count and IL-6 had an OR of 9.85 (95% CI=3.04-31.99), and those in the middle/top tertiles had an OR of 5.40 (95% CI=1.83-15.92) (P<.001, trend test) for frailty. These results were validated in the merged WHAS I and II.
Conclusion: Higher WBC counts and IL-6 levels were independently associated with prevalent frailty in community-dwelling older women.