A hormone in the body that signals the brain when a person is 'full' could help in the fight against Alzheimer's disease, according to the latest research.
Leptin, produced by fat cells, prevents over-eating by sending the brain a "feeling full" message. Scientists have now linked increased amounts of leptin to a reduced chance of suffering Alzheimer's.
There is growing evidence that the hormone also benefits brain development and function, and memory.
Earlier research has shown that it reduces levels of beta-amyloid protein in the brain, a major component of the sticky deposits that are a key hallmark of Alzheimer's.
In the latest study, published in the Journal of the American Medical Association, scientists carried out regular brain scans on 198 older volunteers after measuring their leptin levels.
Over a 12-year follow-up period, a quarter of those with the lowest levels of leptin developed Alzheimer's compared with 6% of those with the highest levels.
Higher leptin concentrations were also associated with greater total brain volume.
Study leader Dr Sudha Seshadri, from Boston University Medical Center in the US, said: "If our findings are confirmed by others, leptin levels in older adults may serve as one of several possible biomarkers for healthy brain ageing and, more importantly, may open new pathways for possible preventive and therapeutic intervention."