Clinical course of early and late mild cognitive impairment: Neuropsychology/Neuropsychological profiles of dementia: Valid biomarkers?

Background Amnestic mild cognitive impairment can be sorted to early mild cognitive impairment (EMCI) or late mild cognitive impairment (LMCI) according to severity of memory impairment. The aim of present study is to compare the prognosis and clinical course between EMCI and LMCI. Method From January 2009 to December, 2017, we recruited 640 participants from memory and dementia clinic at the Neurology Department of Taipei Veteran General Hospital. All patients receive at least two series neuropsychological evaluation annually and were categorized to EMCI or LMCI according to ADNI‐2 criteria. Result Total 186 patients with EMCI and 277 patients with LMCI were included. 177 cognitive normal participants were also included as normal control. The mean follow‐up duration was 2.85 ± 2.02 years (minimal: 1, maximum: 9 years). At the secondary year, 58 (31.2%) EMCI and 9 (3.2%) LMCI reversed to normal cognitive status. Annual dementia conversion rates were 1.61, 4.41, 21.98 per person year in NC, EMCI and LMCI groups, respectively. EMCI and LMCI had higher rate of progression to dementia (Log rank test, p<0.001) than normal subjects. Both MCI groups showed significant decline in global function (MMSE) and executive function (digital forward, Trail making test A (time), Trail making test B (line) and verbal fluency) than those in normal subjects. No significant different was found in episodic memory and language function between converters and non‐converters Conclusion Both early and late MCI showed higher risk of dementia. Although MCI showed wide variation in neuropsychological tasks and clinical diagnosis during follow‐up periods, there was higher global and executive functional decline.