A study has identified four distinct clusters of symptoms, including psychiatric and cardiovascular, that can progressively lead to Alzheimer's disease -- an ageing-related condition in which memory and speech steadily declines, eventually disrupting daily activities.

Researchers from the University of California, Los Angeles, US, said the study offers new insights into how the disorder can develop over time rather than from isolated risk factors.

"We found that multi-step trajectories can indicate greater risk factors for Alzheimer's disease than single conditions," first author Mingzhou Fu, a medical informatics pre-doctoral student at the University of California, said.