A study has discovered why people with Alzheimer's might develop Parkinson's and vice versa.
Findings from the research, which investigated the proteins involved in neurodegenerative diseases, can now be used to help model and develop new drugs, the scientists say.
Dr Eliezer Masliah, professor of neurosciences and pathology at the University of California San Diego School of Medicine, led the study.
She said that although doctors already knew that having one neurological disease put patients at risk for another in combination with it, they did not understand why this occurred.
"Until now," Dr Masliah commented.
"With this novel technology, we have come to a new understanding of these combined neurological diseases and have a model for developing new drugs to treat them."
Earlier this week US research suggested that surgery can halt the loss of dopamine cells in animals.
Scientists said the finding could influence when Parkinson's treatments are administered.
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