Depressive syndromes and risk of dementia in later life: Is the relationship between syndromes of depression and dementia temporal?

Objective To determine associations of depressive syndromes and depression with dementia in older populations who have marked differences in their putative risk factors. Methods 1736 people aged >=65 years in China and 5222 elders in the UK were interviewed using the Geriatric Mental State questionnaire. Five levels of syndromes of depression and dementia were identified, and their diagnosed cases were validated. The Chinese were re-interviewed in 1 year and the British in 2 years and 4 years respectively. Results There was a significant cross-sectional relationship between syndrome levels of depression and dementia. This held in different age, gender and people with and without (CVD) for both Chinese and British populations. Association of syndromes of baseline depression with follow-up dementia were less substantial; correlation coefficient in the Chinese was 0.068 (95%CI -0.010-0.145) for men and 0.089 (0.014-0.163) for women, and in the British further reduced for men but slightly increased for women. Multinomial logistic regression showed no obvious dose-response relationship, but incident dementia was associated with depressive syndromes or depression at levels >= 4 (although not with those at levels 3 - also clinical depression, or less). Multiple adjusted odds ratio in level >= 4 depression was 24.64 (p=0.007) for the Chinese, and 3.14 and 3.83 for the British (both p=0.004). Conclusions The relationship between syndromes of depression and dementia might be temporal. But the most severe syndromes or cases of depression significantly increased the risk of incident dementia. Reducing the severity and relieving symptoms of depression may prevent dementia.