Combined effect of adiposity and elevated inflammation on incident type 2 diabetes: a prospective cohort study

Adiposity and elevated inflammation are two hallmarks of hyperglycemia. However, it is unknown whether clustering of elevated inflammation and adiposity interact act on diabetogenesis and lead to a greater risk for incident type 2 diabetes (T2D).

Adiposity was indicated by body mass index, waist circumference and ultrasonography-measured fatty liver degrees. Elevated inflammation was indicated as high-sensitivity C-reactive protein levels ≥ 2 mg/L. Time-to-event survival analyses were conducted to investigate the joint effect of adiposity and inflammation on incident T2D on both multiplicative and additive scales.

Among 82,172 non-diabetic participants from a prospective cohort in China, 14,278 T2D occurred over a median follow-up of 11 years. In the multivariable-adjusted model, elevated inflammation [1.12 (1.08‒1.16)] and adiposity [1.76 (1.69‒1.83) for overweight/obesity, 1.49 (1.44‒1.55) for central obesity, and 2.02 (1.95‒2.09) for fatty liver] were significantly associated with incident diabetes. Higher adiposity-associated risks and incidence rates of diabetes were observed with elevated inflammation. When studying the joint effect, the adjusted HRs were 1.77 (1.69‒1.85) for overweight/obesity, 1.14 (1.06‒1.23) for elevated inflammation, and 2.08 (1.97‒2.19) for their joint effect, with a relative excess risk due to interaction of 0.17 (0.05‒0.28). The attributable proportions were 71.30% for overweight/obesity, 12.96% for elevated inflammation, and 15.74% for their interaction. Similar results were observed when adiposity was assessed as waist circumference or fatty liver.

Adiposity and elevated inflammation synergically lead to greater risks of incident diabetes than addition of each individual exposure. Strategies simultaneously targeting both risks should produce more benefits for diabetes prevention than through initiatives directed at each separate risk.