Is depression in those with Alzheimer’s Disease different to depression in those without dementia?

Abstract Background Depression in individuals with Alzheimer’s disease (AD) is common, distressing, difficult to treat, may increase carer burden and is inadequately understood. It occurs more frequently in AD than in older adults without dementia. The reasons why some patients develop depression during AD and others do not remain obscure. We aimed to identify risk factors for depression in AD using 3 large cohort studies and assess whether these risk factors differed from those for depression in people with normal cognition. Method We used data from 3 large dementia focused cohorts: ADNI (n = 665 with AD, 669 normal cognition), NACC (n = 698 with AD, 711 normal cognition) and BDR (n = 757 with AD). Depression ratings were available using the GDS & NPI and in addition for BDR the Cornell. Intermittent depression was defined as one episode above threshold and persistent as ≥ 2 episodes. A cut‐off of ≥8 was used for the GDS and the Cornell Scale for Depression in Dementia, ≥6 for the NPI depression sub‐scale and ≥2 for the NPI‐Q depression sub‐scale. We used logistic regression and a random‐effects meta‐analysis to examine potential risk factors and an interaction term to look for interactions between each risk factor and the presence of cognitive impairment. Because we aimed to study persistent depression any participants with only study visit were excluded from the analysis, as were those with treated depression who did not meet criteria for caseness at any point. Result In individual studies there was no evidence of a difference in risk factors for depression in AD but combining data with meta‐analysis suggested clear differences between risk factors for depression in AD and depression in those without dementia e.g. gender (figure 1). Previous depression increased the risk in the only study with this information (OR 7.78 95%CI 4.03‐15.03). Conclusion Risk factors for depression in AD appear to differ to those for depression per se supporting suggestions of a different pathological process. We have identified that a past history of depression is the strongest risk factor for the development of depression in AD, but information on this was only available for one cohort.