Quick takes

Reviewing alcohol's effects on normal sleep

February, 2013

A review on the immediate effects of alcohol on sleep has found that alcohol shortens the time it takes to fall asleep, increases deep sleep, and reduces REM sleep.

Because sleep is so important for memory and learning (and gathering evidence suggests sleep problems may play a significant role in age-related cognitive impairment), I thought I’d make quick note of a recent review bringing together all research on the immediate effects of alcohol on the sleep of healthy individuals.

The review found that alcohol in any amount reduces the time it takes to fall asleep, while greater amounts produce increasing amounts of deep sleep in the first half of the night. However, sleep is more disrupted in the second half. While increased deep sleep is generally good, there are two down sides here: first, it’s paired with sleep disruption in the second half of the night; second, those predisposed to problems such as sleepwalking or sleep apnea may be more vulnerable to them. (A comment from the researchers that makes me wonder if the relationship between deep sleep and slow-wave activity is more complicated than I realized.)

Additionally, at high doses of alcohol, REM sleep is significantly reduced in the first half, and overall. This may impair attention, memory, and motor skills. Moreover, at all doses, the first REM period is significantly delayed, producing less restful sleep.

The researchers conclude that, while alcohol may give the illusion of improving sleep, it is not in fact doing so.

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[3269] Ebrahim IO, Shapiro CM, Williams AJ, Fenwick PB. Alcohol and Sleep I: Effects on Normal Sleep. Alcoholism: Clinical and Experimental Research [Internet]. 2013 :n/a - n/a. Available from: http://onlinelibrary.wiley.com/doi/10.1111/acer.12006/abstract

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Chewing ability linked to reduced dementia risk

January, 2013

A large study of older adults suggests that being able to bite into a hard food such as an apple puts you in a better state to fight cognitive decline and dementia.

Previous research has pointed to an association between not having teeth and a higher risk of cognitive decline and dementia. One reason might have to do with inflammation — inflammation is a well-established risk factor, and at least one study has linked gum disease to a higher dementia risk. Or it might have to do with the simple mechanical act of chewing, reducing blood flow to the brain. A new study has directly investigated chewing ability in older adults.

The Swedish study, involving 557 older adults (77+), found that those with multiple tooth loss, and those who had difficulty chewing hard food such as apples, had a significantly higher risk of developing cognitive impairments (cognitive status was measured using the MMSE). However, when adjusted for sex, age, and education, tooth loss was no longer significant, but chewing difficulties remained significant.

In other words, what had caused the tooth loss didn’t matter. The important thing was to maintain chewing ability, whether with your own natural teeth or dentures.

This idea that the physical act of chewing might affect your cognitive function (on a regular basis; I don’t think anyone is suggesting that you’re brighter when you chew!) is an intriguing and unexpected one. It does, however, give even more emphasis to the importance of physical exercise, which is a much better way of increasing blood flow to the brain.

The finding also reminds us that there are many things going on in the brain that may deteriorate with age and thus lead to cognitive decline and even dementia.

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Cognition impaired by low-level exposure to organophosphate pesticides

January, 2013

A meta-analysis has concluded that low-level exposure to organophosphates has a small-to-moderate negative effect on cognitive function.

Organophosphate pesticides are the most widely used insecticides in the world; they are also (according to WHO), one of the most hazardous pesticides to vertebrate animals. While the toxic effects of high levels of organophosphates are well established, the effects of long-term low-level exposure are still controversial.

A meta-analysis involving 14 studies and more than 1,600 participants, reveals that the majority of well-designed studies undertaken over the last 20 years have found a significant association between low-level exposure to organophosphates and impaired cognitive function. Impairment was small to moderate, and mainly concerned psychomotor speed, executive function, visuospatial ability, working memory, and visual memory.

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Caffeine may block inflammation linked to cognitive impairment

November, 2012

A mouse study indicates that caffeine can help prevent inflammation occurring in the brain, by blocking an early response to cell damage.

Caffeine has been associated with a lower of developing Alzheimer's disease in some recent studies. A recent human study suggested that the reason lies in its effect on proteins involved in inflammation. A new mouse study provides more support for this idea.

In the study, two groups of mice, one of which had been given caffeine, were exposed to hypoxia, simulating what happens in the brain during an interruption of breathing or blood flow. When re-oxygenated, caffeine-treated mice recovered their ability to form a new memory 33% faster than the other mice, and the caffeine was observed to have the same anti-inflammatory effect as blocking interleukin-1 (IL-1) signaling.

Inflammation is a key player in cognitive impairment, and IL-1 has been shown to play a critical role in the inflammation associated with many neurodegenerative diseases.

It was found that the hypoxic episode triggered the release of adenosine, the main component of ATP (your neurons’ fuel). Adenosine is released when a cell is damaged, and this leakage into the environment outside the cell begins a cascade that leads to inflammation (the adenosine activates an enzyme, caspase-1, which triggers production of the cytokine IL-1β).

But caffeine blocks adenosine receptors, stopping the cascade before it starts.

The finding gives support to the idea that caffeine may help prevent cognitive decline and impairment.

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Are sleep problems a key factor in Alzheimer’s?

October, 2012

A mouse study shows that sleep deprivation and aggregation of amyloid beta go hand in hand, and may be key players on the road to Alzheimer’s.

I reported a few months ago on some evidence of a link between disturbed sleep and the development of Alzheimer’s. Now a mouse study adds to this evidence.

The mouse study follows on from an earlier study showing that brain levels of amyloid beta naturally rise when healthy young mice are awake and drop after they go to sleep, and that sleep deprivation disrupted this cycle and accelerated the development of amyloid plaques. This natural rhythm was confirmed in humans.

In the new study, it was found that this circadian rhythm showed the first signs of disruption as soon as Alzheimer’s plaques began forming in the mice’s brains. When the genetically engineered mice were given a vaccine against amyloid beta, the mice didn’t develop plaques in old age, the natural fluctuations in amyloid beta levels continued, and sleep patterns remained normal.

Research with humans in now underway to see whether patients with early markers of Alzheimer’s show sleep problems, and what the nature of these problems is.

Just to make it clear: the point is not so much that Alzheimer’s patients are more likely to have sleep problems, but that the sleep problems may in fact be part of the cause of Alzheimer’s disease development. The big question, of course, is whether you can prevent its development by attacking the dysfunction in circadian rhythm. (See more on this debate at Biomed)

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Why metabolic syndrome is linked to cognitive decline?

October, 2012

Preliminary results for a small study indicate metabolic syndrome is linked to significantly reduced blood flow in the brain, perhaps explaining its link to cognitive impairment.

I’ve reported before on the growing evidence that metabolic syndrome in middle and old age is linked to greater risk of cognitive impairment in old age and faster decline. A new study shows at least part of the reason.

The study involved 71 middle-aged people recruited from the Wisconsin Registry for Alzheimer's Prevention (WRAP), of whom 29 met the criteria for metabolic syndrome (multiple cardiovascular and diabetes risk factors including abdominal obesity, high blood pressure, high blood sugar and high cholesterol).

Those with metabolic syndrome averaged 15% less blood flow to the brain than those without the syndrome.

One tried and true method of increasing blood flow to the brain is of course through exercise.

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The study was presented at the Alzheimer's Association International Conference in Vancouver, Canada by Barbara Bendlin.

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Regular cocoa drinking helps those with MCI

September, 2012

Daily consumption of a high level of cocoa was found to improve cognitive scores, insulin resistance and blood pressure, in older adults with mild cognitive impairment.

Back in 2009, I reported briefly on a large Norwegian study that found that older adults who consumed chocolate, wine, and tea performed significantly better on cognitive tests. The association was assumed to be linked to the flavanols in these products. A new study confirms this finding, and extends it to older adults with mild cognitive impairment.

The study involved 90 older adults with MCI, who consumed either 990 milligrams, 520 mg, or 45 mg of a dairy-based cocoa drink daily for eight weeks. Their diet was restricted to eliminate other sources of flavanols (such as tea, red wine, apples and grapes).

Cognitive assessment at the end of this period revealed that, although scores on the MMSE were similar across all groups, those consuming higher levels of flavanol cocoa took significantly less time to complete Trail Making Tests A and B, and scored significantly higher on the verbal fluency test. Insulin resistance and blood pressure was also lower.

Those with the highest levels of flavanols did better than those on intermediate levels on the cognitive tests. Both did better than those on the lowest levels.

Changes in insulin resistance explained part, but not all, of the cognitive improvement.

One caveat: the group were generally in good health without known cardiovascular disease — thus, not completely representative of all those with MCI.

 

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Childhood music training has enduring benefits for hearing

September, 2012

More evidence that learning a musical instrument in childhood, even for a few years, has long-lasting benefits for auditory processing.

Adding to the growing evidence for the long-term cognitive benefits of childhood music training, a new study has found that even a few years of music training in childhood has long-lasting benefits for auditory discrimination.

The study involved 45 adults (aged 18-31), of whom 15 had no music training, 15 had one to five years of training, and 15 had six to eleven years. Participants were presented with different complex sounds ranging in pitch while brainstem activity was monitored.

Brainstem response to the sounds was significantly stronger in those with any sort of music training, compared to those who had never had any music training. This was a categorical difference — years of training didn’t make a difference (although some minimal length may be required — only one person had only one year of training). However, recency of training did make a difference to brainstem response, and it does seem that some fading might occur over long periods of time.

This difference in brainstem response means that those with music training are better at recognizing the fundamental frequency (lowest frequency sound). This explains why music training may help protect older adults from hearing difficulties — the ability to discriminate fundamental frequencies is crucial for understanding speech, and for processing sound in noisy environments.

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[3074] Skoe E, Kraus N. A Little Goes a Long Way: How the Adult Brain Is Shaped by Musical Training in Childhood. The Journal of Neuroscience [Internet]. 2012 ;32(34):11507 - 11510. Available from: http://www.jneurosci.org/content/32/34/11507

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Controlling diabetes important for slowing cognitive decline

August, 2012

Findings from a large, long-running study adds to growing evidence that poorly controlled diabetes is associated with faster cognitive decline.

The latest finding from the large, long-running Health, Aging, and Body Composition (Health ABC) Study adds to the evidence that preventing or controlling diabetes helps prevent age-related cognitive decline.

The study involves 3,069 older adults (70+), of whom 717 (23%) had diabetes at the beginning of the study in 1997. Over the course of the study, a further 159 developed diabetes. Those with diabetes at the beginning had lower cognitive scores, and showed faster decline. Those who developed diabetes showed a rate of decline that was between that faster rate and the slower rate of those who never developed diabetes.

Among those with diabetes, those who had higher levels of a blood marker called glycosylated hemoglobin had greater cognitive impairment. Higher levels of this blood marker reflect poorer control of blood sugar.

In other words, both duration and severity of diabetes are important factors in determining rate of cognitive decline in old age.

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Benefits of omega-3 in preventing age-related cognitive decline not proven

August, 2012

A review of research into omega-3 oils' benefits for fighting cognitive decline concludes that there is no evidence, but that longer-term research is needed.

A review of three high quality trials comparing the putative benefits of omega-3 fatty acids for preventing age-related cognitive decline, has concluded that there is no evidence that taking fish oil supplements helps fight cognitive decline. The trials involved a total of 3,536 healthy older adults (60+). In two studies, participants were randomly assigned to receive gel capsules containing omega-3 PUFA or olive or sunflower oil for six or 24 months. In the third study, participants were randomly assigned to receive tubs of margarine spread for 40 months (regular margarine versus margarine fortified with omega-3 PUFA).

The researchers found no benefit from taking the omega-3 capsules or margarine spread compared to placebo capsules or margarines (sunflower oil, olive oil or regular margarine). Participants given omega-3 did not score better on the MMSE or on other tests of cognitive function such as verbal learning, digit span and verbal fluency.

The researchers nevertheless stress that longer term studies are needed, given that there was very little deterioration in cognitive function in any of the groups.

Reference: 

[3015] Sydenham E, Dangour AD, Lim W-S. Omega 3 fatty acid for the prevention of cognitive decline and dementia. In: Collaboration TC, Sydenham E Cochrane Database of Systematic Reviews. Cochrane Database of Systematic Reviews. Chichester, UK: John Wiley & Sons, Ltd; 2012. Available from: http://summaries.cochrane.org/CD005379/fish-oils-for-the-prevention-of-dementia-in-older-people

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