Association of the phase angle with type 2 diabetes and related traits: results from two prospective KORA studies

OBJECTIVES: To investigate associations of the bioelectrical impedance analysis (BIA)-derived phase angle (PhA), an indicator of body cell mass, hydration status, and cell membrane integrity, with type 2 diabetes (T2D), prediabetes, and glycemic and insulin-related traits. METHODS: Using data from the Cooperative Health Research in the Region of Augsburg (KORA) S3/S4 studies, we analyzed 7728 participants aged 25-74 years for prevalent T2D and 7006 participants who did not have diabetes at baseline for incident T2D. A subsample aged 55-74 years at S4 was followed to assess incident oral glucose tolerance test (OGTT)-defined prediabetes or T2D (prediabetes/T2D), and glycemic and insulin-related traits (S4/F4/FF4). The PhA was calculated from BIA 2000-S at 50 kHz. Logistic and Cox regressions were applied for binary outcomes, and two-level growth models for continuous traits. RESULTS: In S3/S4, 324 participants had prevalent T2D at baseline, and 707 developed T2D during a median 15.7-year follow-up. In S4/F4/FF4, during up to 14 years of follow-up, 251 out of 626 normoglycemic participants at S4 developed incident prediabetes/T2D, and 792-804 participants without diabetes at S4 had three repeated measurements of continuous traits. The PhA (per 1-degree) was positively associated with incident T2D (hazard ratio [HR] and 95% confidence interval [CI] in S3/S4: 1.37 [1.21-1.54]) and incident prediabetes/T2D (HR [95% CI] in S4/F4/FF4: 1.33 [1.07-1.67]) without sex differences. The PhA (per 1-degree) was also positively associated with fasting glucose (beta [95% CI]: 1.2% [0.1-2.2%]) and insulin resistance (beta [95% CI]: 7.0% [2.3-11.7%]) cross-sectionally, and with changes in 2-h glucose longitudinally (beta [95% CI]: 4.5% [2.3-6.7%]) (S4/F4/FF4). In contrast, the PhA (per 1-degree) was inversely associated with prevalent T2D (odds ratio [95% CI] in S3/S4: 0.72 [0.56-0.93]) in men only. CONCLUSIONS: The PhA at 50 kHz had stage-dependent associations with glucose metabolism, with higher values observed during subclinical stages and lower values after diabetes manifestation.