We thank Panza and colleagues for their interesting observation regarding the discrepancy in the incidence of dementia in MCI between the CHS-CS1 and the ILSA.2 One of the most important epidemiological problems in the study of MCI and dementia is the ascertainment of cases. Studies using a 2-stage screening protocol risk missing MCI and early dementia cases (eg, a cut-off of 23 in Mini-Mental State Examination score).2 In the CHS-CS, all subjects had detailed neurological and neuropsychological evaluations, and none of them went through a screening phase. Had we used a cut-off score of 80 in the Modified Mini-Mental State Examination (which is the accepted cut-off for identifying cognitively impaired subjects, similar to a Mini-Mental State Examination score of about 23),3 we would have failed to identify 86% of the subjects eventually classified as MCI and 53% of those with dementia.
Lopez OL, Kuller LH, Becker JT. Progression to Dementia in Probable and Possible Mild Cognitive Impairment—Reply. Arch Neurol. 2007;64(8):1210-1211. doi:10.1001/archneur.64.8.1210