No Protection Against Mental Decline as We Age? Say It Ain’t So!
For years I’ve been recommending measures to help prevent mental the decline and dementia associated with advanced age. Measures immediately coming to mind are the Mediterranean diet, exercise, not smoking, avoiding obesity, eating cold-water fatty fish regularly (for the omega-3 fatty acids), and keeping the mind active.
Turns out there’s not much good evidence ( but there’s some) in support of that advice, according to a study commissioned by the National Institutes of Health and published this month in Annals of Internal Medicine.
The investigators did a literature review of the best-designed studies looking for associations between about 45 factors and the risk of cognitive decline in later life. It’s a little unclear, but this report seems to focus on mild cognitive impairment rather than dementia such as Alzheimer disease. Mild cognitive impairment is often a precursor to dementia such as Alzheimer disease. The review included 127 observational studies, 22 randomized controlled trials, and 16 systematic reviews.
The list of cognitive decline risk factors (and protective factors) included the apoliprotein E epsilon-4 gene, smoking, diabetes, physical activity, alcohol consumption, obesity, Mediterranean diet, omega-3 intake, and many others.
For all of the factors, the investigators found insufficient evidence from which to draw firm conclusions. They are fairly confident that statin drugs and aspirin are not associated with cognitive decline.
They found high-quality evidence for only one factor that protects against cognitive decline: cognitive training (involving memory, reasoning, and speed).
They noted that overall quality of the scientific evidence is low [so there’s hope they missed some protective effects?].
Another report in the same issue of Annals focused on Alzheimer disease and was similarly disappointing in terms of action we can take now to prevent cognitive decline and Alzheimer dementia. Beaucoup experts and thousands of man-hours were devoted to this report. Here’s a depressing line:
Currently, firm conclusions cannot be drawn about the association of any modifiable risk factor with cognitive decline or Alzheimer disease.
Now What?
Enjoy life while you can, and plan ahead for possible cognitive decline.
Hope and pray the researchers come up with some solutions soon. There’s a tsunami of dementia in our future.
I still think the Mediterranean diet (and perhaps some of the other factors analyzed) may be brain-protective, and here’s why. Note that the reviewers of these studies point out we have “no high-quality studies upon which to base firm conclusions.” The reviewers gave most credence to randomized controlled trials. And with good reason: such studies are probably the best way to prove that a medical or dietary intervention is effective. Observational studies, on the other hand, can point to associations, which may have nothing to do with cause and effect.
Here’s how you do a randomized controlled trial to see if the Mediterranan diet has a long-term effect on cognitive function. Take 5,000 adults aged 3o to 50 and make half of them eat the Mediterranean diet and the other half eat a specific standard diet. Keep all other variables the same for both groups. Over the course of 30-40 years, monitor the changes in cognition in all individuals and compare the two groups. That study has the potential to yield high-quality data and proof.
Problem is, it’ll probably never be done because it’s close to impossible. It’s hard enough to get a free-living 40-year-old to follow a new way of eating for 12 weeks, much less 30 years. That’s why so much population-wide nutrition research is observational. Most, but not all, of the studies supporting the brain-protective properties of the Mediterranean diet are observational. I’m not aware of a single randomized controlled study on the long-term cognitive effects of the Mediterranean diet.
And one more thing . . .
The NIH reports at hand didn’t look at the synergy among factors that individually may have only tiny positive effects. For instance, what if you combine the Mediterranean diet with physical activity, non-smoking, mind-stimulating activities, and avoidance of diabetes and obesity? Could have a winning combo there!
Sounds like I’m grasping at straws, doesn’t it?
I’m not prepared yet to abandon idea of the brain-protective Mediterranean diet.
References:
Brenda L. Plassman, PhD; John W. Williams Jr., MD, MHSc; James R. Burke, MD, PhD; Tracey Holsinger, MD; and Sophiya Benjamin, MD (2010). Systematic review: NIH state-of-the-science conference: Factors associated with risk for and possible prevention of cognitive decline in later life.
Annals of Internal Medicine, 152
Daviglus ML, Bell CC, Berrettini W, Bowen PE, Connolly ES Jr, Cox NJ, Dunbar-Jacob JM, Granieri EC, Hunt G, McGarry K, Patel D, Potosky AL, Sanders-Bush E, Silberberg D, & Trevisan M (2010). National Institutes of Health State-of-the-Science Conference Statement: Preventing Alzheimer Disease and Cognitive Decline. Annals of internal medicine PMID: 20547888
June 18th, 2010 at 8:31 am
You put your finger on the sore point: It is too expensive to do long-term studies that - let’s face it - make no money for the big funding agents, namely drug firms.
But population studies of native people and religious groups that follow mostly vegetarian diets have shown that thry do better, health-wise.
We know already what to do - I am all with the Mediterranean diet. Now we just have to do it. And teach it.
Alexa Fleckenstein M.D., physician, author.
June 19th, 2010 at 5:18 am
This is why we need to do lab experiments. Im not sure what has been done on this but maybe there has been experiments on rats etc. More omega 3 = less brain degradation perhaps. This would suggest protective effects. As you stated the main problem with the studies you mention is controlling ALL the variables. There are so many confounding factors. One person might be eating lots of fish, but not do anything in terms of training the brain thus negating what they eat.
June 20th, 2010 at 12:40 pm
Enjoyed reading your post. A trend in research seems to suggest lifestyle factors that are good for physical health are also good for mental health. It’s hard to imagine that a combination of exercise and a healthy diet wouldn’t offer benefits to the brain which is so intricately connected with the body.
June 21st, 2010 at 2:43 am
Alexa, I remember reading all about those healthy groups in Dan Buettner’s “Blue Zones” book.
-Steve