Objective To examine the temporal relation between depression and cognitive impairment in old age. Design Prospective, population based study with four years of follow up. Setting City of Leiden, the Netherlands. Participants 500 people aged 85 years at recruitment. Main outcome measures Annual assessments of depressive symptoms (15 item geriatric depression scale), global cognitive function (mini-mental state examination), attention (Stroop test), processing speed (letter digit coding test), and immediate and delayed recall (12 word learning test). Results At 85 years old, participants' depressive symptoms and cognitive impairment were highly significantly correlated (P < 0.001). During follow up, an accelerated annual increase of depressive symptoms was associated with impaired attention (0.08 points (95% confidence interval 0.01 to 0.16)), immediate recall (0.17 points (0.09 to 0.25)), and delayed recall (0.10 points (0.02 to 0.18)) at baseline. In contrast, depressive symptoms at baseline were not related to an accelerated cognitive decline during follow up (P > 0.05). Conclusion Caregivers should be aware of the development of depressive symptoms when cognitive impairment is present. However, the presence of depression only does not increase the risk of cognitive decline.

In community dwelling elderly, those with vascular disease were at higher risk of developing apathy but not depression. This suggests that apathy and depression in old age have different etiologies.

The data suggest that the increased mortality risk attributable to depression in the presence of perceived loneliness may result from motivational depletion.

In the population at large, generalized atherosclerosis contributes to cognitive decline in old age but not to depression.

This study shows that the GDS-15 detects change in depressive symptoms after loss of a partner, a negative life event that is the most important risk factor for depression in the elderly. Therefore, it may be concluded that the GDS-15 has the ability to measure longitudinal alterations in depressive symptomatology.