Is late onset depression a prodrome to dementia?

BACKGROUND: Recent research suggests there are clinical and biological differences between late onset depression (LOD) and early-onset depression (EOD). OBJECTIVES: In this paper we review clinical, epidemiological, structural neuroimaging and genetic investigations of late life depression that have been performed over the past two decades and offer evidence that LOD is often a prodromal disorder for dementia. RESULTS: LOD patients are more likely to have cognitive impairment and to have more deep white matter lesions (DWMLs). Evidence concerning cortical and temporal lobe atrophy is conflicting, while the ApoE 4 allele is not associated with LOD. CONCLUSIONS: It is likely that LOD is not a prodrome for a particular type of dementia, but the majority of patients who do develop dementia will acquire Alzheimer's disease (AD) or a vascular dementia, as these are by far the most common causes of dementia. This issue requires further clarification with follow-up of patients over the long term.