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Diabetes and cognitive decline

31 Jan

More on the connection between diabetes and dementia. A paper published in the journal Diabetologia looked at HbA1c levels (a marker for diabetes) and diabetes status in relationship to cognitive status in large (N =  51,89) longitudinal study. Their findings:

Significant longitudinal associations between HbA1c levels, diabetes status and long-term cognitive decline were observed in this study.

I do have one concern about how this study is being reported in the media. For example, this piece in the Atlantic states

A high-carb diet, and the attendant high blood sugar, are associated with cognitive decline.

It should say “a high refined carb diet.” The distinction is important, simple sugars and refined carbohydrates should be avoided. Note that the same article recommends the Mediterranean Diet, a diet that actually includes a lot of unrefined carbohydrates. As the Harvard Medical Letter reports:

The carbohydrates in Mediterranean-style diets tend to come from unrefined, fiber-rich sources like whole wheat and beans.

400 failed Alzheimer’s drugs

15 Jan

An article in The Washington Post examines why it is so hard to find an effective drug to treat Alzheimer’s disease:

These setbacks pile on to an already depressing situation: more than 400 failed clinical trials since the last Alzheimer’s drug — which only treats the symptoms of the disease, temporarily — was approved more than a decade ago.

(…)

Alzheimer’s is a formidable foe for a number of reasons. The brain isn’t easy to access, and much about how it works remains mysterious, even as scientific knowledge has moved forward. Doctors can’t take easy, repeat biopsies to see whether a drug is working.

Trials are long and expensive. It has become increasingly clear that it is necessary to treat patients early in the disease, and then wait to see if the disease is prevented or slowed.

Patients, though they are affected in heartbreaking ways, typically are unable to act as advocates for more funding or research when they are in the throes of the disease — unlike cancer or AIDS patients.

Does extra virgin olive oil prevent Alzheimer’s disease?

12 Jan

Sound too good to be true? It probably is. Here is a post on the topic by Joy Victory:

To deconstruct how this went off the rails, let’s start with the university news release sent to journalists: “Temple study: Extra-virgin olive oil preserves memory & protects brain against Alzheimer’s.”

That’s a headline that surely got journalists’ attention. It’s not until after two very long opening paragraphs extolling the virtues of the nearly magical powers of extra virgin olive oil that we find out who, exactly this was tested on.

Mice.

Andrew Gelman gives his take:

I looked briefly at the published research article and am concerned about forking paths, type M errors, and type S errors. Put briefly, I doubt such strong results would show up in a replication of this study.

Is Alzheimer’s caused by brain atherosclerosis?

3 Jan

Please  understand that this explanation if one of a number of competing hypotheses. Dr. Greger makes his case here:

B vitamins may slow cognitive decline

28 Aug

Dr. Greger takes a look at the most recent work on the cognitive effects of B vitamins:

Initially, the results were disappointing. Vitamin supplementation did not seem to work, but the studies were tracking neuropsychological assessments, which are more subjective compared to structural neuroimaging—that is, actually seeing what’s happening to the brain. A double-blind randomized controlled trial found that homocysteine-lowering by B vitamins can slow the rate of accelerated brain atrophy in people with mild cognitive impairment. As we age, our brains slowly atrophy, but the shrinking is much accelerated in patients suffering from Alzheimer’s disease. An intermediate rate of shrinkage is found in people with mild cognitive impairment. The thinking is if we could slow the rate of brain loss, we may be able to slow the conversion to Alzheimer’s disease. Researchers tried giving people B vitamins for two years and found it markedly slowed the rate of brain shrinkage. The rate of atrophy in those with high homocysteine levels was cut in half. A simple, safe treatment can slow the accelerated rate of brain loss.

A follow-up study went further by demonstrating that B-vitamin treatment reduces, by as much as seven-fold, the brain atrophy in the regions specifically vulnerable to the Alzheimer’s disease process.

Some thoughts on memory and age

14 Aug

There is a general decline in memory with age that seems to affect all of us, this is called benign senescent forgetting  and is not considered pathological. Naturally, we find this forgetting disconcerting. Fortunately, however, there is evidence that we can reduce the effects of benign senescent forgetting. We know that environmental factors must be important because there are differences between generations in performance on memory tests. Standard scores for psychological tests are set by administering the large representative samples of the general population. When tests are restandardized we can compare changes in test performance across generations. For example, one study found that 61 – 75 years olds tested in 2007, performed better than 61 – 75 year olds tested in 1985. The improvements were substantial and must have some environmental cause since the human genome could not have substantially changed in the intervening decades.
The fact that environmental factors must affect memory is heartening news, because it suggests that memory improvement is possible.
However, benign senescent forgetting remains frightening and we worry that it may be an early sign of dementia. Our fear of Alzheimer’s disease and other forms of dementia may not be misplaced. Even if average memory performance of older people has been improving, as life expectancy increases a larger percentage of us may succumb to dementia.
Dementia is a degenerative brain disorder. Memory loss is the major symptom of dementia, but patients also exhibit other forms of intellectual decline.
In the United States 5% of those between the ages of 71 and 79 years suffer from dementia, while 37.4% of those 90 and older suffer from dementia. Alzheimer’s disease accounts for 69.9 cases of dementia. Vascular dementia accounts for another 17.4%. The reaming 12.7% includes Parkinson’s dementia, traumatic brain injuries, alcoholic dementia, and other causes.
There is evidence that we can reduce our risks of dementia. Physical exercise, healthy diet, cognitive engagement, and memory training do seem to offer some protection.

Higher childhood IQ related to a lower risk mortality

3 Jul

The Lothian birth-cohort studies continue to contribute to our understanding of cognitive aging. Here is the latest paper, published in the journal Intelligence. And here are the paper’s highlights;

• 94% of the participants of the Scottish Mental Survey 1947 were traced.
• Higher childhood IQ was related to a lower risk of all-cause mortality by age 79.
• The effect was slightly stronger in women than in men.
• The decline in risk across categories of IQ scores was graded across the full range.
•This is the only study of IQ and mortality in an entire year-of-birth cohort.

Here is Ian Deary’s brief description of the Lothian birth-cohort studies

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