The Association Of Late Life Depression On Cognitive Function

ObjectivesTo explore the relationship between depression and mild cognitive impairment in the elderly,and whether there is a dose-response relationship between the severity of depression and the occurrence of mild cognitive impairment.Further,to investigate whether baseline depression is related to cognitive decline over time.Study design and methodsData in this study was derived from the European Survey of Health,Aging,and Retirement in Europe(SHARE).Depression was assessed by a 12-item Europe-depression scale(European-Depression,EURO-D).Cognition was measured on three cognitive domains:immediate recall,delayed recall and verbal fluency.A composite score of global cognition was calculated by averaging these three cognitive domains.Mild cognitive impairment was determined by 1.5 standard deviations below the global cognition.In part one,a total of 12759 people over 60 years old without mild cognitive impairment were followed-up for an average of 8 years to explore the associations of baseline depression and the severity of depression with mild cognitive impairment using Cox regression models,we also performed stratified analyses by age to estimate whether age could modify the association between depression and dementia.In part two,13013 people over 60 years were follow-up for an average of 9 years to estimate cognitive decline in relation to baseline depression status using linear mixed model.Results1.The relationship between baseline depression and mild cognitive impairmentDuring 11 years of follow-up,1602(12.56%)incident mild cognitive impairment cases were identified.After adjusting for age,gender,education,country,smoking,drinking,living status,BMI,chronic disease,and physical activity,compared with non-depression,people with baseline depression had a higher risk of mild cognitive impairment(HR=1.43,95%CI:1.28-1.61).Further analysis showed that this association was only existed in those aged 60-79 years(HR=1.48,95%CI:1.31-1.68),but not in people over 80 years old(HR=1.12,95%CI:0.80-1.56).In addition,there was a dose-response relationship between the severity of depression and the risk of mild cognitive impairment:the higher the depressive scores,the higher risk of mild cognitive impairment(P<0.001).2.The effect of baseline depression on cognitive declineThe results from the linear mixed model showed that people with depression had lower cognitive function in immediate memory(?:-0.197,95%CI:-0.239,-0.154),delayed memory(?:-0.181,95%CI:-0.225,-0.137),verbal fluency(?:-0.132,95%CI:-0.172,-0.091)and global cognition(?:-0.169,95%CI:-0.203,-0.135)after adjusting for age,gender,education,country,smoking,drinking,living status,BMI,chronic disease,and physical activity.However,late life depression was not related to the rate of cognitive decline(P>0.05).ConclusionsLate life depression increased the risk of mild cognitive impairment in a dose-response fashion among people aged 60-79 years.However,depression was not related to the rate of cognitive decline in later life.