Comparison of Neuropsychological and FDG-PET Findings between Early- versus Late-Onset Mild Cognitive Impairment: A Five-Year Longitudinal Study

Abstract

Aims: Our purpose was to investigate differences in neuropsychological characteristics and glucose metabolism between early-onset mild cognitive impairment (EOMCI) and late onset MCI (LOMCI) patients and to determine if the baseline differences are predictive of conversion to dementia. Methods: We enrolled 28 patients with MCI (12 EOMCI, 16 LOMCI) and 2 age-matched control groups. At the end of a 5-year follow-up, we compared the baseline neuropsychological and PET data between converters and nonconverters. Results: The EOMCI patients obtained significantly higher scores in verbal recall and word fluency tests than the LOMCI patients. The EOMCI group, compared to the young controls, demonstrated hypometabolism in brain regions vulnerable in mild Alzheimer’s disease. Converters were significantly more impaired in the delayed verbal recall test than nonconverters (p = 0.028) and tended to be more impaired in the semantic word fluency test (p = 0.084). The baseline PET scan of the converters demonstrated severer hypometabolism in frontal areas than that of the nonconverters both in the EOMCI and LOMCI groups. Conclusion: Our study suggests that EOMCI patients may differ from LOMCI in the patterns of cognitive deficits and glucose hypometabolism. In addition, baseline neuropsychological and FDG-PET findings suggest that MCI patients with poor memory or frontal dysfunction are at greater risk of conversion to dementia.