Eat fish, exercise to keep mind keen
Studies encouraging for middle-aged, people prone to mental decline
Running or bicycling to the fish market may be just the right medicine for staying sharp mentally, according to a pair of new studies.
One study finds eating fish at least once a week is good for the brain, slowing age-related mental decline by the equivalent of three to four years.
The other study makes the startling find that people who exercise in middle age are far less likely to develop Alzheimer's disease and other types of dementia when they are older.
Doctors have long realized that regular exercise could prevent and control high blood pressure, diabetes and heart disease. But recent studies, including the newest one, have pointed to the more surprising finding that exercise can protect against the development of senility, even many years later.
In a study published last week online by the journal Lancet Neurology, researchers from the Karolinska Institute in Sweden checked for dementia or Alzheimer's in a group of nearly 1,500 patients 65 and older whose exercise habits have been monitored for nearly 35 years.
To the researchers' surprise, they found that people who engaged in leisure-time physical activity at least twice a week as they passed through middle age had a 50 percent lower chance of developing dementia and a 60 percent lower chance of developing Alzheimer's disease, compared with more sedentary people.
"If an individual adopts an active lifestyle in youth and at midlife, this may increase their probability of enjoying both physically and cognitively vital years later in life," said Dr. Miia Kivipelto of the Aging Research Center of Karolinska Institute in Stockholm and the main author of the study.
The diet research adds to the growing evidence that a fish-rich diet helps keep the mind sharp. Previous studies found that people who ate fish lowered their risk of Alzheimer's disease and stroke. Fish such as salmon and tuna that are rich in omega-3 fatty acids also have been shown to prevent heart disease.
For the new study, researchers measured how well 3,718 people did on simple tests, such as recalling details of a story. The participants, all Chicago residents 65 and older, took the tests three times over six years. They also filled out a questionnaire about what they ate that included 139 foods.
We found that people who ate one fish meal a week had a 10 percent
slower annual decline in thinking," said co-author Martha Clare Morris,
an epidemiologist at Rush University Medical Center. "Those who ate two
fish meals a week showed a 13 percent slower annual decline.
At the same time, the Food and Drug Administration warns pregnant women, nursing mothers and children to avoid certain types of fish with high levels of mercury - shark, swordfish, king mackerel or tilefish. Mercury can damage the growing brains of fetuses and children.
The study of fish and mental sharpness was posted Monday on the Web site of the Archives of Neurology and will appear in the journal's December issue. It was published early online because of its general interest.
The Swedish study about fitness and mental acuity does not prove cause and effect, and it is possible that people predisposed to Alzheimer's exercised less for some reason connected to the disease. But the study's finding confirms what has recently been hinted at by previous, smaller studies in animals and humans.
"This is important and squares well with what we've come to realize in the past five years," said Ian H. Robertson, director of the Trinity College Institute of Neurosciences in Dublin, Ireland. "It shouldn't be surprising that the brain benefits from exercise like the rest of the body, perhaps even more."
Robertson added that this was the first study he knew of to show a specific link between exercise and preventing Alzheimer's.
To ensure that the exercise habit was in and of itself protective, rather than just a general marker for a healthier person or healthy habits, the researchers adjusted their study to eliminate other influences such as age, sex, education, movement disorders, vascular illness, smoking and alcohol consumption.
More limited studies have recently suggested that diet and intellectual activity, as well as physical exercise, may prevent the mental decline associated with aging.
The announcement last week deals primarily with the benefits of long-term exercise on the brain.
The researchers were not able to specify an exact mechanism. They noted that dementia starts with silent neurological changes, detectable under a microscope years before outward signs appear.
Recent research on mice genetically engineered to develop Alzheimer's hints at a more specific biochemical explanation.
In a study published in April in The Journal of Neuroscience, a group of those mice were given treadmills in their cages, and so the opportunity to run in their "leisure time."
In a series of subsequent intellectual challenges, the running mice proved better able to learn the ins and outs of test mazes, learning escape routes twice as fast as their more sluggish counterparts.
More important, when the mice were autopsied, the brains of the active ones showed far fewer deposits of beta amyloid. Deposits of clumps of this protein are characteristic of Alzheimer's, in mice and man.