The apparent lack of correlation between changes in Dkk-1 and disease progression in MCI may be attributable to the slower natural progression in MCI compared with dementia given the relatively short duration of follow-up in our study (Storandt et al., 2002), as well as the etiological heterogeneity of MCI, although patients with non-amnestic presentations as well as central nervous or systemic conditions that could potentially contribute to cognitive impairment were excluded. Here, DKK1 is linked to Cognitive impairment.