TFRC and nutritional disorder: Regarding the other definitions of iron deficiency, the IR per 100 person-years was 4.5 (95% CI 4.0–4.9) for ferritin < 45 μg/L, 2.4 (95% CI 2.2–2.7) for ferritin < 30 μg/L, and 12.2 (95% CI 11.0–13.5) for sTfR–ferritin index > 1.5.