by Craig Weatherby
Rarely do health headlines overlap as strikingly as they did earlier this week.
Two separate studies concerning links among diet, dementia, and blood pressure were released on Monday, February 8, 2010.
One was an MRI brain-scan study from Columbia University, which showed that people who follow a Mediterranean-style diet closely had much less brain damage in the regions of the brain responsible for “executive” functions.
The other was a report linking high blood pressure to increased risk of dementia among older people who display mild decline in their brain’s executive functions (thinking and decision-making).
The Columbia team equated the degree of protection provided by Mediterranean-style diets to the kind of protection provided by low blood pressure ... hence the intriguing overlap.
Let’s take a quick look at both investigations … starting with some very good news about Mediterranean diets and brain health.
MRI study suggests Mediterranean diet may deter brain damage
Researchers from Manhattan’s Columbia University Medical Center conducted the new study with support from the National Institutes of Health (AAN 2010).
They recruited 712 New Yorkers, and determined their diets using questionnaires.
Then, they separated the volunteers into three groups, based on how closely they were following the ideal Mediterranean diet, centered on fruits, vegetables, whole grains, fish, nuts, and extra virgin olive oil.
To learn more about that diet, see “Mediterranean Myths: Region's Actual Diets Differ from Ideal”.
Six years later, the Columbia team used MRI machines to scan the participants’ brains, and one in three (238) showed at least one area of brain damage.
(The kind of damage they saw using MRI scans is called an infarct… a term that means tissue damage caused by inadequate blood supply. Heart and brain infarcts are often caused when an artery narrows or shuts due to the plaque buildup called atherosclerosis… or by related blood clots.)
The MRI scans showed that the people whose diets resembled the ideal Mediterranean diet closest were 36 percent less likely to have areas of brain damage, compared with those whose diets fell furthest from it.
People whose diets approached the ideal Mediterranean diet less closely were 21 percent less likely to have brain damage, compared with those whose diets were least Mediterranean-like.
The observation that links this study to the other one we report today came from lead author Nikolaos Scarmeas, M.D.:
“The relationship between this type of brain damage and the Mediterranean diet was comparable with that of high blood pressure. In this study, not eating a Mediterranean-like diet had about the same effect on the brain as having high blood pressure” (AAN 2010).
Research published last year by Dr. Scarmeas and his colleagues associated Mediterranean-style diets with a lower risk of Alzheimer’s disease and indicated that these diets—and exercise—may extend the life-spans of its victims (Scarmeas N et al. Feb. 2009; Scarmeas N et al. Aug. 2009).
Their new study indicates that these associations may be partially explained by the lesser amount of damaged brain tissue that their MRI scans found in people who followed the ideal Mediterranean-style diet most closely.
Faltering executive functions + high blood pressure = Alzheimer’s risk
Having hypertension in middle age is a proven risk factor for developing cognitive impairments that can progress to Alzheimer's disease or other forms of dementia.
This is because hypertension is a major risk factor for tissue damage resulting from inadequate blood supply to distinct areas of the brain.
But it’s not been clear whether having hypertension later in life promotes dementia.
People with mild cognitive (thinking, learning and memory) impairment—the stage before actual dementia—experience different kinds of brain deficits.
Researchers from two universities set out to discover whether hypertension increases the risk of dementia more in people with certain kinds of cognitive dysfunction than in people other kinds (Oveisgharan S, Hachinski V 2010).
Scientists from Canada’s University of Western Ontario and from Iran’s Isfahan University recruited 990 older adults (average age 83) with cognitive impairment but no outward signs of dementia.
Over a five-year follow-up period, dementia developed at approximately the same rate among participants with and without hypertension (59.5 percent of people with high blood pressure versus 64.2 percent of those without it).
A similar pattern was observed among those with memory dysfunction alone and those who had memory and executive dysfunction
However, among the people who showed only loss of executive function, hypertension was associated with a greatly increased risk of developing dementia… specifically, 57.7 percent of those with high blood pressure progressed to dementia, versus only 28 percent of those without.
As the researchers wrote, “Control of hypertension in this population could decrease by one-half the… rate of progression to dementia” (Oveisgharan S, Hachinski V 2010).
Of course, few of us know which, if any, kind of cognitive impairment we may have—or be progressing toward.
So this finding really means that everyone should watch their blood pressure and consider hypertension a risk factor for dementia.
- Oveisgharan S, Hachinski V. Hypertension, executive dysfunction, and progression to dementia: the Canadian study of health and aging. Arch Neurol. 2010 Feb;67(2):187-92.
- Scarmeas N, Stern Y, Mayeux R, Manly JJ, Schupf N, Luchsinger JA. Mediterranean diet and mild cognitive impairment. Arch Neurol. 2009 Feb;66(2):216-25.
- Scarmeas N, Luchsinger JA, Schupf N, Brickman AM, Cosentino S, Tang MX, Stern Y. Physical activity, diet, and risk of Alzheimer disease. JAMA. 2009 Aug 12;302(6):627-37
- American Academy of Neurology (AAN). Mediterranean Diet May Lower Risk of Brain Damage That Causes Thinking Problems. February 8, 2010. Accessed at http://www.aan.com/press/index.cfm?fuseaction=release.view&release=796