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.