It's puzzled me that obesity was associated with earlier onset of Alzheimer's. It makes sense that both the obesity and the dementia might arise from a common cause ...
BBC News - Alzheimer's risk linked to level of appetite hormone
High levels of a hormone that controls appetite appear to be linked to a reduced risk of developing Alzheimer's disease, US research suggests.
The 12-year-study of 200 volunteers found those with the lowest levels of leptin were more likely to develop the disease than those with the highest.
The JAMA study builds on work that links low leptin levels to the brain plaques found in Alzheimer's patients....
... Research on mice - conducted to establish why obese patients with diabetes often have long-term memory problems - found those who received doses of leptin were far more adept at negotiating their way through a maze.
The latest research, carried out at Boston University Medical Center, involved regular brain scans on 198 older volunteers over a 12-year period.
A quarter of those with the lowest levels of leptin went on to develop Alzheimer's disease, compared with 6% of those with the highest levels.
"If our findings our 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."...
That's a huge relative risk - a 4 times higher incidence of dementia. Note that the mouse did better when given leptin (though mice seem to do better with just about anything). There's some interest in using leptin to prevent and treat Alzheimer's.
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