Internal fat mediates the impact of age on diabetes onset in chinese people between 30 and 44 years old.

AIMS: We sought to measure the effect of controlling body fat indexes on decreasing the incidence of type 2 diabetes mellitus (T2DM) mathematically. METHODS: Study samples were selected from a well-established cohort in Suzhou, China between 2004 and 2008, comprising 6364 males and 9678 females. The questionnaire contained socio-demographic characteristics, smoking, alcohol consumption, diet, physical activity, personal and family medical history and current medication. Multiple linear regression, Cox regression and mediation analyses were performed to determine the relationship among age, body fat indexes and T2DM onset. RESULTS: All the three body fat indexes [the body mass index (BMI), waist-to-hip ratio (WHR) and body fat percentage] showed a significant positive association (P<0.05) with age and T2DM. Significant indirect effects (IE) were detected for age, which were mediated respectively through WHR [IE=1.10, 95%CI: 1.07-1.13; P<0.001], the BMI (IE=1.15, 95%CI: 1.11-1.18; P<0.001), and body fat percentage (IE=1.09, 95%CI: 1.07-1.12; P<0.001). The combined body fat index score demonstrated a significant association with age (P<0.001) and a stronger relationship with the onset of diabetes (P<0.001) along with a significant mediating effect (IE=1.17; 95%CI: 1.13-1.22; P<0.001). The total effect of age on T2DM was 1.60 (95%CI: 1.21-2.10; P=0.0008). As a result, the three body fat indexes jointly mediated 33.97% of the age impact on diabetes onset. CONCLUSIONS: This pilot study revealed important roles for body fat indexes in mediating the age pathway to the onset of diabetes. Controling body fat in the appropriate range could reduce 33.97% of the risk of T2DM onset with increasing age.