The order of causation may be the other way around for whatever association there is between diabetes and Alzheimer disease, if a hypothesis about a genetic variant in insulin processing related to Alzheimer disease holds up.
But right now it is much too early to say yes to to the question posed in the headline of the submitted article. The underlying study
has several desirable design features for a human nutrition study, but it still needs to be replicated, and it's an observational study, not an experimental study, so we don't know what kinds of interventions are likely to be of most help in preventing Alzheimer disease.
See another thread just posted by another HN participant
about how rarely supposed breakthrough medical discoveries are even replicated. Don't believe the easy, breakthrough answers until they have been verified.
The comment responding to my The New York Times recently seems to be willing to give up its journalistic reputation in the medical stories on its hosted blogs and go straight for eyeballs at any price in credibility is of course correct that the New York Times has disclosed that the writer is writing as a blogger, not as a journalist. I think it's regrettable that he nonetheless is able to slap the New York Times brand on an overly speculative post that assumes matters of fact that are not well verified. I'm not sure if all readers are as aware as many HN participants that some long-established journalistic organizations host blogging webpages that have no editorial oversight. I think it would be helpful for readers to be able to distinguish at a glance what sources are professionally edited, and which are people doing their own personal expressions of opinion.
So then I found this paper, which discusses Alzheimer's and insulin, and suggests rosiglitazone as a possible treatment:
And here's how that worked:
And that's pretty amazing, considering it has been my understanding that there are no effective treatments for Alzheimer's. A successful prediction is also the gold standard of scientific evidence. Unfortunately, the floor fell through on rosiglitazone:
More circumstantial evidence shows up in the fact that coffee, known to improve insulin sensitivity, is correlated with a reduced risk of Alzheimer's:
And the kicker is this paper from 2005...
"Impaired insulin and insulin-like growth factor expression and signaling mechanisms in Alzheimer's disease - is this type 3 diabetes?"
So now we know where the NYT got its headline. And this may not be as loony as I originally thought. Are they right? Well, we thought we had Alzheimer's figured out about four different times now. First it was choline, then it was amyloid plaques, then it was tau phosphorylation, then it was aluminium toxicity, now it's insulin resistance.
This has the potential to be extraordinary, but I'm not holding my breath.
Known? I've seen interventional studies on the effects of caffeine claiming effects in either direction. Here are two studies showing decreased insulin sensitivity:
Effects of Coffee Consumption on Fasting Blood Glucose and Insulin Concentrations (http://care.diabetesjournals.org/content/27/12/2990.full)
Caffeine Impairs Glucose Metabolism in Type 2 Diabetes (http://care.diabetesjournals.org/content/27/8/2047.extract)
>Higher habitual coffee consumption was associated with higher insulin sensitivity (1) and a lower risk for type 2 diabetes (2–6) in diverse populations. In contrast, short-term metabolic studies showed that caffeine intake can acutely lower insulin sensitivity (7–9) and increase glucose concentrations (10–15). Randomized intervention studies are needed to examine whether tolerance to these acute effects develops after longer-term consumption (16). We therefore examined the effects of coffee and caffeine on fasting blood concentrations of glucose and insulin over 2–4 weeks in two crossover studies in healthy volunteers.
So caffeine causes a problem, but something in coffee, possibly not caffeine itself ( http://ajcn.nutrition.org/content/84/4/682.short ), has a long-term protective effect. Weight control doesn't seem to explain everything: coffee has a protective effect even when consumption is associated with higher BMI ( http://www.sciencedirect.com/science/article/pii/S0140673602... ). In the latter study: "Higher coffee consumption was associated with male sex, a low educational level, a higher body-mass index, cigarette smoking, alcohol use, less leisure time physical activity, and a generally less favourable diet" -- these are not things I would expect to be good for diabetes prevention! Yet the coffee consumers got less diabetes.
Chlorogenic acid, rather than caffeine, seems a likely culprit. Other antioxidants in coffee may play a role.
Regardless of the fact that it's written by a man who resigned from the NYTimes because of plagiarism, it's still interesting imo.
The gist is: the body is complex, so complex that often research mistakes causality with a simple accumulation of facts.
Keep holding your breath.
The author is listed as an "Opinionator columnist". I think that's nytimes-speak for "blogger".
Been down that road before with the NYT, "The Google Way: Give Engineers Room" ~ http://www.flickr.com/photos/bootload/1685662827/in/set-7215...
Any reporting on new theories within science will include things for which it is "too early to say yes to the question posed in the headline". And any such reporting can easily be criticized for "going straight for eyeballs".
I guess what is new is that newspapers have been marginalized to a degree that otherwise well educated people no longer necessarily know the editorial conventions that govern them.
I am confused.