Depression shows that a patient is at risk of developing Alzheimer’s rather than being an early sign of the disease, according to a study.
During the onset of the disease, the study found no evidence of an increase in depression before Alzheimer’s was diagnosed.
The findings come after a study of 917 elderly Catholic clergy at Rush Alzheimer’s Disease Centre in the US.
Many studies have found associations between depression in old age and the occurrence of Alzheimer’s and mild cognitive impairment.
But they had not been able to find whether depressive symptoms contributed to the development of dementia or were a consequence of the disease.
Researchers examined data from the Rush Religious Orders Study, a research project into 917 older Catholic clergy without dementia when the study began.
They looked at changes in depressive symptoms of Alzheimer’s before and after the emergence of the symptoms of the disease that relate to loss of thought processes, such as learning, comprehension, memory, reasoning, and judgment.
The clergy underwent clinical trials for up to 13 years including assessment of depressive symptoms, cognitive testing and clinical classification of mild cognitive impairment and Alzheimer’s disease.
During this period, some 190 developed Alzheimer’s disease.
Having more depressive symptoms at baseline was linked with a rise in incidence of Alzheimer’s disease and mild cognitive impairment.
But those who developed Alzheimer’s disease showed no increase in depressive symptoms before clinical diagnosis, the study found.
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