Table 1.

Patient characteristics

Characteristic	Normal	MCI
No. of patients	91	72
No. of females (%)	55 (60)	31 (43)
Mean (SD) age at second scan, years	81.9 (7.5)	80.0 (7.7)
Mean (SD) education, years of schooling at baseline	13.5 (3.0)	13.7 (3.6)
Median (IQR) MMSE score at time of second scan	29 (28, 30)	26 (25, 28)
Mean (SD) time between scans, years	1.4 (0.3)	1.3 (0.4)
No. of observed conversions*	13	39
Median (95% CI) time to conversion, years	---†	3.2 (2.1, 3.7)
Median (range) length of conversion-free follow-up‡, years	3.4 (0.9, 10.9)	1.9 (0.9, 9.0)

^*, Normal subjects converted to MCI (11) or AD (2), MCIs converted to AD

^†, This quantity cannot be estimated because the survivorship curve did not drop below 0.5 due to the small number of events.

^‡, Follow-up time defined as time from second scan to conversion, censoring, or last follow-up among those who remained stable.