Excessive iron intake was associated with an increased risk of all-cause dementia in those aged ≥65 years old (M3: HR (95% CI): Q5:Q4: 1.92 (1.10–3.35), p = 0.021), without hypertension (M3: Q5:Q4: 1.44 (1.01, 2.05), p = 0.041), without diabetes (M3: Q5:Q4: 1.46 (1.09, 1.95), p = 0.011) and non-APOE4 carriers (M3: Q5:Q4: 1.53 (1.05, 2.23), p = 0.027). Here, APOE is linked to diabetes mellitus.