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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.

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.


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.

“Sugary beverage intake and preclinical Alzheimer’s disease”

26 Apr

For some years I have been intrigued by the idea that Alzheimer’s disease might be a special type of diabetes (sometimes called Type 3 Diabetes). You can read the evidence for this hypothesis here.

A recent study published in the journal Alzheimer’s and Dementia reports the observation that sugary drink consumption may be linked to Alzheimer’s disease. Here is the abstract:

Excess sugar consumption has been linked with Alzheimer’s disease (AD) pathology in animal models.

We examined the cross-sectional association of sugary beverage consumption with neuropsychological (N = 4276) and magnetic resonance imaging (N = 3846) markers of preclinical Alzheimer’s disease and vascular brain injury (VBI) in the community-based Framingham Heart Study. Intake of sugary beverages was estimated using a food frequency questionnaire.

Relative to consuming less than one sugary beverage per day, higher intake of sugary beverages was associated with lower total brain volume (1–2/day, β ± standard error [SE] = −0.55 ± 0.14 mean percent difference, P = .0002; >2/day, β ± SE = −0.68 ± 0.18, P < .0001), and poorer performance on tests of episodic memory (all P < .01). Daily fruit juice intake was associated with lower total brain volume, hippocampal volume, and poorer episodic memory (all P < .05). Sugary beverage intake was not associated with VBI in a consistent manner across outcomes.

Higher intake of sugary beverages was associated cross-sectionally with markers of preclinical AD.

This result would be consistent with the Type 3 Diabetes hypothesis. But note that the study is correlational and based on self-report. Sugary beverage consumption might be a proxy for some other variable.

Can rosemary improve cognition?

3 Apr

Perhaps, but only at very low doses. Dr. Greger explains. Note that the study suggests that too much rosemary might interfere with cognition.

I did find the results about aromatherapy interesting. I had always assumed that the idea was implausible. But Dr. Greger points to a study that shows that the volatile compounds used can actually be measured in the blood. This doesn’t mean that aromatherapy works, only that it’s plausible.

High blood pressure and dementia

9 Nov

A paper published in the journal Hypertension, here is the abstract:

Background—Age-related dementia, most commonly caused by Alzheimer disease or cerebrovascular factors (vascular dementia), is a major public health threat. Chronic arterial hypertension is a well-established risk factor for both types of dementia, but the link between hypertension and its treatment and cognition remains poorly understood. In this scientific statement, a multidisciplinary team of experts examines the impact of hypertension on cognition to assess the state of the knowledge, to identify gaps, and to provide future directions.

Methods—Authors with relevant expertise were selected to contribute to this statement in accordance with the American Heart Association conflict-of-interest management policy. Panel members were assigned topics relevant to their areas of expertise, reviewed the literature, and summarized the available data.

Results—Hypertension disrupts the structure and function of cerebral blood vessels, leads to ischemic damage of white matter regions critical for cognitive function, and may promote Alzheimer pathology. There is strong evidence of a deleterious influence of midlife hypertension on late-life cognitive function, but the cognitive impact of late-life hypertension is less clear. Observational studies demonstrated a cumulative effect of hypertension on cerebrovascular damage, but evidence from clinical trials that antihypertensive treatment improves cognition is not conclusive.

Conclusions—After carefully reviewing the literature, the group concluded that there were insufficient data to make evidence-based recommendations. However, judicious treatment of hypertension, taking into account goals of care and individual characteristics (eg, age and comorbidities), seems justified to safeguard vascular health and, as a consequence, brain health.

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