I think this is an important paper reporting on a well-conducted study.
Although cross-sectional, the results imply a subtle continuum from
cognitive complaints through to mild cognitive impairment and on to
Alzheimer disease. Using a good-sized cohort of 40 subjects with
cognitive complaints, 40 MCI subjects, and 40 controls, Saykin and
colleagues used both voxel-based methods and region-of-interest outlining to show
that relative to the control group, the MCI group had lower hippocampal
volumes and lower grey matter densities in medial temporal lobe and
elsewhere; importantly, they also showed that the group with cognitive
complaints (but without cognitive deficits to meet MCI criteria) had
hippocampal and grey matter volumes intermediate between the two groups.
The paper therefore provides further, albeit circumstantial, evidence
that structural changes—and in particular medial temporal lobe grey
matter losses—may be detectable before cognitive deficits become
manifest. It also reminds us that in certain settings, cognitive
complaints should be taken seriously...