WEDNESDAY, June 24 (HealthDay News) -- To stave off the mental decline associated with old age, engage in intellectually challenging activities, maintain a positive outlook and keep up your social life.

Those are the findings of what researchers say is the largest-ever review of studies on aging and the brain.

The review, which spanned three decades and covered more than 400 studies, found that remaining physically, mentally and socially active has a substantial impact on whether older adults experience declines in memory and cognition, which includes the ability to learn and solve problems.

"How people spend their lives does really have an impact on how they age cognitively," said study co-author Robert S. Wilson, a professor of neurological and behavioral sciences at Rush University Medical Center in Chicago. "The observational studies suggest people who are more intellectually active, socially integrated, physically active and who are relatively free from negative emotions like depression and anxiety all seem to be associated with aging better cognitively."

As the U.S. population ages, being able to keep mental decline at bay for even a little longer could have significant public health implications.

A hundred years ago, only about 4 percent of the U.S. population was older than 65. In 2000, that group reached more than 12 percent. By 2030, an estimated 20 percent will be older than 65.

Along with this, the prevalence of Alzheimer's disease is expected to quadruple over the next 40 years, Wilson said.

"There is going to be a huge burden of old people who are cognitively impaired," Wilson said. "If we can develop strategies that delay the onset of the disease by six months or a year or two, we can substantially reduce the human suffering and the cost of caring for them."

The study, which will appear in Psychological Science in the Public Interest, was released June 24 in Washington, D.C.

It identified several aspects of a person's lifestyle that can have a major impact on mental function: exercise, staying socially integrated, participating in mentally stimulating activities and maintaining an optimistic, agreeable, goal-oriented attitude.

Though exercise had a powerful impact on mental function, the type of exercise made a difference.

In studies that asked older people how physically active they were, those who reported doing the most exercise had somewhat better mental functioning than those who were more sedentary, but the effect wasn't dramatic.

However, people who took part in studies that put them on a regular aerobic exercise program saw substantial gains in mental functioning.

Among older adults, even those who do relatively more exercise than their peers probably aren't doing all that much, Wilson said.

"Left to their own devices, most older people in this country don't exercise all that much at all," Wilson said. "Any exercise is good, but actually doing a regular program of aerobic exercise is better."

Walking, the most commonly cited exercise, can be part of an aerobic exercise program, but the pace must be fast enough to raise the heart rate.

Recent research has looked at whether specific products or programs, such as video games, improve cognitive functioning in older people. Although there is nothing on the market that is scientifically proven to increase memory and thinking skills, Wilson said, he thinks such products could be available soon.

But you don't have to go out and buy something to engage in intellectually stimulating activities, said Dr. Gary Kennedy, director of geriatric psychiatry at Montefiore Medical Center in New York City.

Doing a crossword puzzle, playing chess or learning a language can fit the bill. Research shows that taking part in activities that are novel, challenging and in which you are personally invested can have a lasting impact on mental functioning.

"The reality is, as we age, cognitive processes slow down," Kennedy said. "It may take you longer, and you may have to practice longer to master something new, but hopefully you have health and the time to actually do that."

Though cognitive decline was once seen as an inescapable part of aging, public perception is beginning to change, and recent studies back that up.

"Most people's brains are under assault in old age, and the lifestyle stuff doesn't appear to stop that pathology," Wilson said. "But lifestyle does appear to help your brain tolerate that pathology. It helps you get more out of what you have left and to adapt to the changes in your brain, and it appears to make a big difference."

In an accompanying editorial, Jonathan W. King and Richard Suzman, from the U.S. National Institute of Aging, said that the study's findings overall paint a "fairly optimistic" picture.

"It could well be possible to design interventions that, when combined with appropriate lifestyle changes, could possibly at least slow the rate of cognitive decline," they wrote.

More information

The Fisher Center for Alzheimer's Research Foundation has more on Alzheimer's and dementia  .

TUESDAY, June 23 (HealthDay News) -- If you eat a healthy diet, you're likely to live longer.

It might be trite advice, but a new study offers proof that it can make a difference in your longevity.

Those with the best diets reduced their risk of death by up to 25 percent over a 10-year follow-up, said study author Ashima Kant, a professor of nutrition at Queens College of the City University of New York.

Kant and her colleagues extracted information from a National Institutes of Health/AARP database including more than 350,000 men and women, evaluating the link between dietary habits and their risk of death during the follow-up period. They divided the participants into five groups, depending on how closely they followed the 2005 USDA Dietary Guidelines for Americans.

"If you had the highest fifth of these scores, your risk of dying over the follow-up period was 20 to 25 percent lower," Kant said. She found gender differences, with women eating the healthiest reducing their risk of death by 25 percent and men reducing it by 20 percent.

"We have been advocating these kinds of behaviors for a while," she said. Other studies have found a survival benefit but have tended to look only at individual foods, she said. "This gets at looking at all these dietary features in a collective way," she said.

Kant's team asked the participants about six components of a healthy diet, including intake of fruits, vegetables, low-fat dairy, whole grains, lean meat and poultry, and fat.

People didn't have to eat perfectly to get a top score, she said. For instance, "if a person had five or six servings of vegetables a week, that would get them the top score [for that question]," she said.

"It's not that you have to do everything [recommended under the dietary guidelines] to have any health benefits," she said, noting that participants in the groups with lower (but not the lowest) scores also tended to live longer. For instance, women who were in the second-from-the-highest group on dietary scores were 20 percent less likely to die and men in that group were 17 percent less likely.

The study is published in the July issue of The Journal of Nutrition.

Good dietary habits may also help delay the progression of hardening of the arteries, according to a separate study published in the July issue of the The American Journal of Clinical Nutrition. Researchers from Tufts University and Wake Forest University evaluated the effect of a good diet on the progression of coronary artery disease in 224 postmenopausal women who had the disease when they enrolled in the Estrogen Replacement and Atherosclerosis Study. The better the diet, the slower the progression of disease, they found.

"Both studies are finding similar things," said Penny Kris-Etherton, a distinguished professor of nutrition at Penn State University, who wrote an editorial to accompany the atherosclerosis study.

"We're getting more and more evidence that diet [when poor] can play a key role in chronic disease development, progression and all-cause mortality," she said.

Will the findings -- especially the fact that those who got the top benefit didn't eat perfectly -- inspire people?

"As a nutritionist, you try to be optimistic and hope so," Kris-Etherton said. "But society sometimes makes it difficult. We live in an environment where there are so many food choices that aren't consistent with our [dietary] guidelines."

More information

To learn more about the dietary guidelines, visit the U.S. Department of Health and Human Services.

MONDAY, June 22 (HealthDay News) -- Not only is vinegar low in calories, but it might actually help avoid weight gain, a new study suggests.

In a study in mice, Japanese researchers fed one group a high-fat diet along with acetic acid, a main component of vinegar, for six weeks. The others were fed a high-fat diet and given water.

Mice in both groups gained weight, but the mice who consumed acetic acid gained up to 10 percent less than those given water, the study found. The results are in the July 8 issue of the Journal of Agricultural and Food Chemistry.

In the lab, researchers found the acetic acid inhibited the accumulation of body fat and hepatic lipids, which include cholesterol and triglycerides, by increasing the expression of genes involved in fatty acid oxidation.

The genes produce proteins that help break down fats, preventing the fat from being stored by the body.

Vinegar, used throughout the world as a condiment and a preservative, has been used as a folk medicine for thousands of years, including to treat scurvy during the U.S. Civil War and to treat wounds during World War I, according to the Vinegar Institute.

Recent research has shown that vinegar might help control blood pressure, blood sugar levels and fat accumulation.

So does this mean you should douse your fish and chips with malt vinegar to make it healthier? The study didn't address vinegar's potential to help humans stay slim, but you can dream.

More information

The Vinegar Institutes has more on vinegar  , including its history and recipes.

MONDAY, June 22 (HealthDay News) -- People in the United States and around the world who are trying to lower their "bad" cholesterol have been succeeding more often in the past decade, new research suggests.

The look at almost 10,000 patients from nine countries found that, overall, 73 percent had reached their target level of low-density lipoprotein (LDL) -- nearly double the number since the survey was first conducted in 1996-1997. Three-quarters of those surveyed were on a statin drug to lower cholesterol (for an average duration of about two years), while others either used different medications or made only lifestyle changes, such as improved exercise and nutrition regimens, to try to bring down their LDL levels, the researchers found.

In the United States, patients of all levels of risk for coronary heart disease showed improvement from their initial 38 percent success rate in 1996-1997. Of those considered at low risk, 86 percent met their target LDL level; 74 percent of moderate-risk patients reached their goal; and 67 percent in the high-risk category hit their mark, according to the findings, published in the current issue of Circulation.

LDL is known as "bad" cholesterol because it is associated with increased cardiovascular risk. A person's risk category was based on factors such as having existing coronary artery disease, being obese, diabetic, a smoker and having other known links to heart disease. LDL targets were based on these risk categories, ranging from less than 160 milligrams per deciliter for those at low risk to less than 70 milligrams per deciliter for those considered very high risk, according to a news release from the American Heart Association.

The only real disappointment internationally was in the category of those considered at very high risk, where only 30 percent met their target, the study authors noted.

"Although there is room for improvement, particularly in very high-risk patients, these results indicate that lipid-lowering therapy is being applied much more successfully than it was a decade ago," study author Dr. David D. Waters, a professor emeritus of medicine at the University of California, San Francisco, said in the news release.

The rates of achieving the LDL goals ranged from 47 percent in Spain to 84 percent in South Korea, a variation the researchers were at a loss to explain. The other countries in the study, besides the United States, were Brazil, Canada, France, Mexico, the Netherlands and Taiwan.

The study was funded by Pfizer, Inc., maker of the statin drug, Lipitor.

More information

The National Cholesterol Education Program has more about high blood cholesterol.