Personality may influence brain shrinkage in aging

Previous research has been equivocal about whether cognitive training helps cognitively healthy older adults. One recent review concluded that cognitive training could help slow age-related decline in a range of cognitive tasks; another found no evidence that such training helps slow or prevent the development of Alzheimer’s in healthy older adults. Most of the studies reviewed looked at single-domain training only: memory, reasoning, processing speed, reading, solving arithmetic problems, or strategy training (1).

Genetic analysis of 9,232 older adults (average age 67; range 56-84) has implicated four genes in how fast your hippocampus shrinks with age (rs7294919 at 12q24, rs17178006 at 12q14, rs6741949 at 2q24, rs7852872 at 9p33). The first of these (implicated in cell death) showed a particularly strong link to a reduced hippocampus volume — with average consequence being a hippocampus of the same size as that of a person 4-5 years older.

Data from the very large and long-running Cognitive Function and Ageing Study, a U.K. study involving 13,004 older adults (65+), from which 329 brains are now available for analysis, has found that cognitive lifestyle score (CLS) had no effect on Alzheimer’s pathology. Characteristics typical of Alzheimer’s, such as plaques, neurofibrillary tangles, and hippocampal atrophy, were similar in all CLS groups.

A study involving 1,575 older adults (aged 58-76) has found that those with DHA levels in the bottom 25% had smaller brain volume (equivalent to about 2 years of aging) and greater amounts of white matter lesions. Those with levels of all omega-3 fatty acids in the bottom quarter also scored lower on tests of visual memory, executive function, and abstract thinking.

The finding adds to the evidence that higher levels of omega-3 fatty acids reduce dementia risk.

For more about omega-3 oils and cognition

Previous research has pointed to a typical decline in our sense of control as we get older. Maintaining a sense of control, however, appears to be a key factor in successful aging. Unsurprisingly, in view of the evidence that self-belief and metacognitive understanding are important for cognitive performance, a stronger sense of control is associated with better cognitive performance. (By metacognitive understanding I mean the knowledge that cognitive performance is malleable, not fixed, and strategies and training are effective in improving cognition.)

A number of studies have found evidence that older adults can benefit from cognitive training. However, neural plasticity is thought to decline with age, and because of this, it’s thought that the younger-old, and/or the higher-functioning, may benefit more than the older-old, or the lower-functioning. On the other hand, because their performance may already be as good as it can be, higher-functioning seniors may be less likely to benefit. You can find evidence for both of these views.

Data from 11,926 older twins (aged 65+) has found measurable cognitive impairment in 25% of them and subjective cognitive impairment in a further 39%, meaning that 64% of these older adults were experiencing some sort of cognitive impairment.

A small study of the sleep patterns of 100 people aged 45-80 has found a link between sleep disruption and level of amyloid plaques (characteristic of Alzheimer’s disease). The participants were recruited from the Adult Children Study, of whom half have a family history of Alzheimer’s disease.

Sleep was monitored for two weeks. Those who woke frequently (more than five times an hour!) and those who spent less than 85% of their time in bed actually asleep, were more likely to have amyloid plaques. A quarter of the participants had evidence of amyloid plaques.

A ten-year study following 12,412 middle-aged and older adults (50+) has found that those who died after stroke had more severe memory loss in the years before stroke compared to those who survived stroke and those who didn't have a stroke.

Participants were tested every two years, using a standard word-recall list to measure memory loss (or caregiver assessment for those whose memory loss was too severe). During the decade of the study, 1,027 participants (8.3%) survived a stroke, 499 (4%) died after stroke, and 10,886 (87.7%) remained stroke-free over the study period.

In the study, 64 older adults (60-74; average 70) and 64 college students were compared on a word recognition task. Both groups first took a vocabulary test, on which they performed similarly. They were then presented with 12 lists of 15 semantically related words. For example, one list could have words associated with "sleep," such as "bed," "rest," "awake," "tired" and "night" — but not the word “sleep”. They were not told they would be tested on their memory of these, rather they were asked to rate each word for pleasantness.