Depressive symptoms that develop in midlife or late life are associated with a substantially increased risk of developing dementia, say US researchers.
Almost 14,000 long-standing Kaiser Permanente members were studied and the risk of developing Alzheimer disease or vascular dementia was assessed in those with depressive symptoms recorded in their notes when they were aged between 40 and 55 years old, when they were around 70 years or older, or both.
The overall risk of dementia was increased by 21% in those with midlife depression, 72% for later life depression and 77% for both.
Looking at the two types of dementia, those who only had depression symptoms later in life had a more than two-fold increase in the risk of Alzheimer's (hazard ratio 2.06) while those with both mid and later life symptoms had a more than three-fold increase in vascular dementia (hazard ratio 3.51)
Study leader Dr Kristine Yaffe, a psychiatrist at the University of California, San Francisco, said: ‘We need to know whether adequate treatment of depression in mid or later life helps maintain cognitive function. Even a small reduction in dementia risk would have a tremendous public health impact.'
Arch Gen Psychiatry 2012; 69: 493-498