Figure 5. Schematic: the impact of ferritin and other biomarkers on AD presentation.

(a) CSF ferritin has a qualitatively different impact to (b) CSF tau/Aβ_1–42 and ApoE on cognitive performance over time in cognitively normal (dotted lines) and in subjects who develop AD (solid lines). Higher CSF ferritin levels are associated with poorer baseline cognitive status (for example, RAVLT) by [α] points, where [α]=Ln[ferritin (ng ml⁻¹)]*1·77 (refer to Table 2). This effect is constant over time, such that [α]=[β,χ]. Consequently, ferritin causes a shift to the left in age of conversion to AD by [δ] months, where [δ]=ferritin (ng ml⁻¹)*3 (refer to Fig. 3b). Levels of tau/Aβ_1–42 or ApoE are associated with both baseline cognitive status [ɛ] and the rate of cognitive deterioration, such that [ɛ]<[φ,γ]. The effect causes a shift in age of diagnosis by [η] months where [η]=ApoE (μg ml⁻¹)*8 or tau/Aβ_1–42 (units)*17 (refer to Fig. 3b).