Significant impact of body mass index on the relationship between increased white blood cell count and new-onset diabetes

An elevated white blood cell (WBC) count has been linked to incident diabetes. WBC count has been positively associated with body mass index (BMI), and elevated BMI has been reported to be a strong predictor of future diabetes. Hence, the association of increased WBC count with the subsequent development of diabetes may be mediated by increased BMI. This study was designed to address this issue. We selected subjects from the 104,451 participants enrolled from 2012 to 2018 in the Taiwan Biobank. We only included those with complete data at baseline and follow-up and those without diabetes at baseline. Finally, 24,514 participants were enrolled in this study. During an average 3.88 years of follow-up, 248 (1.0%) of the participants had new-onset diabetes. After adjusting for demographic, clinical, and biochemical parameters, increased WBC count was associated with new-onset diabetes in all of these participants (p ≤ 0.024). After further adjustment for BMI, the association became insignificant (p = 0.096). In addition, subgroup analysis of 23,430 subjects with a normal WBC count (range: 3500-10500/µl) demonstrated that increased WBC count was significantly associated with new-onset diabetes after adjusting for demographic, clinical, and biochemical parameters (p ≤ 0.016). After further adjustment for BMI, this association was attenuated (p = 0.050). In conclusion, our results showed that BMI had a significant impact on the relationship between increased WBC count and new-onset diabetes in all study participants, and BMI also attenuated the association in those with a normal WBC count. Hence, the association between increased WBC count and the future development of diabetes may be mediated by BMI.