A rhesus monkey study has revealed which dendritic spines are lost with age, providing a new target for therapies to help prevent age-association cognitive impairment. It appears that it is the thin, dynamic spines in the dorsolateral prefrontal cortex, which are key to learning new things, establishing rules, and planning, that are lost. Learning of a new task was correlated with both synapse density and average spine size, but was most strongly predicted by the head volume of thin spines. There was no correlation with size or density of the large, mushroom-shaped spines, which were very stable across age and probably mediate long-term memories, enabling the retention of expertise and skills learned early in life. There was no correlation with any of these spine characteristics once the task was learned. The findings underscore the importance of building skills and broad expertise when young.

A special supplement in the Journal of Alzheimer's Disease focuses on the effects of caffeine on dementia and age-related cognitive decline. Here are the highlights:

A mouse study has found memory restoration and lower levels of amyloid-beta in Alzheimer’s mice following only 1-2 months of caffeine treatment. The researchers talk of “ a surprising ability of moderate caffeine intake to protect against or treat AD”, and define moderate intake as around 5 cups of coffee a day(!).

A review of studies into the relation between caffeine intake, diabetes, cognition and dementia, concludes that indications that coffee/caffeine consumption is associated with a decreased risk of Type 2 diabetes and possibly also with a decreased dementia risk, cannot yet be confirmed with any certainty.

A study involving 351 older adults without dementia found the association between caffeine intake and cognitive performance disappeared once socioeconomic status was taken into account.

A study involving 641 older adults found caffeine consumption was significantly associated with less cognitive decline for women only. Supporting this, white matter lesions were significantly fewer in women consuming more than 3 units of caffeine per day (after adjustment for age) than in women consuming less.

A Portuguese study involving 648 older adults found that caffeine intake was associated with a lower risk of cognitive decline in women, but not significantly in men.

A review of published studies examining the relation between caffeine intake and cognitive decline or dementia shows a trend towards a protective effect of caffeine, but because of the limited number of epidemiological studies, and the methodological differences between them, is unable to come up with a definitive conclusion.

A review of published epidemiological studies looking at the association between caffeine intake and Parkinson’s Disease confirms that higher caffeine intake is associated with a lower risk of developing Parkinson’s Disease (though this association may be stronger for men than women). Other studies provide evidence of caffeine’s potential in treatment, improving both the motor deficits and non-motor symptoms of Parkinson’s.

Although research has so far been confined to mouse studies, researchers are optimistic about the promise of histone deacetylase inhibitors in reversing age-related memory loss — both normal decline, and the far more dramatic loss produced by Alzheimer’s. The latest study reveals that memory impairment in the aging mouse is associated with altered hippocampal chromatin plasticity, specifically with the failure of histone H4 lysine 12 acetylation, leading to a failure to initiate the gene expression program associated with memory consolidation. Restoring this acetylation leads to the recovery of cognitive abilities.

Examination of the brains from 9 “super-aged” — people over 80 whose memory performance was at the level of 50-year-olds — has found that some of them had almost no tau tangles. The accumulation of tau tangles has been thought to be a natural part of the aging process; an excess of them is linked to Alzheimer’s disease. The next step is to work out why some people are immune to tangle formation, while others appear immune to the effects. Perhaps the first group is genetically protected, while the others are reaping the benefits of a preventive lifestyle.

A new study provides more support for the idea that cognitive decline in older adults is a product of a growing inability to ignore distractions. Moreover, the study, involving 21 older adults (60-80) shown random sequences of pictures containing faces and scenes and asked to remember only the scene or the face, reveals that being given forewarning about which specific pictures would be relevant (say the second, or the fourth) did not help. The findings suggest that the failure to suppress irrelevant information is not due to a failure in quickly assessing what is relevant, but is a related to mechanisms that occur early in the visual processing stream.