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Prolonged exposure to loud traffic noise is strongly associated with stroke in people aged 65 and older, a new Danish study finds.

The researchers discovered that for every 10 decibels or more of road noise, a person’s risk of having a stroke increased by 14 percent.

For people younger than 65, that did not translate into a statistically significant risk, but researchers found that among those 65 or older, stroke risk increased significantly, by 27 percent for every additional 10 decibels of noise. Also, in older people the researchers found evidence of a threshold limit around 60 decibels, above which the risk of stroke increased still more.

The study involved more than 57,000 people between the ages of 50 and 64 living near Copenhagen and Aarhus who were recruited for the Danish Diet, Cancer and Health cohort study between 1993 and 1997, according to study author Mette Sorensen, senior researcher at the Institute of Cancer Epidemiology of Danish Cancer Society in Copenhagen. The average follow-up time was 10 years.

“Although our study was the first study on traffic noise and stroke, I was not surprised of the results as earlier studies have found traffic noise to be associated with other cardiovascular diseases,” Sorensen said. The study showed only an association between loud noise and stroke, she noted, adding that more research would need to be done to confirm the findings.

The study authors noted that their study took place in an urban area and so was not representative of the whole country. But by taking noise exposures at different dwellings into account and applying the findings across Denmark, Sorensen estimates that 600 new cases of stroke each year in her country could be attributed to road traffic noise. The 5.5 million inhabitants of Denmark suffer 12,400 new cases of stroke annually.

Although the study does not determine how road noise influences health, Sorensen believes stress is likely a factor.

“Exposure to traffic noise is believed to provoke a stress response and disturb sleep, which might increase the risk for stroke, through mechanisms including increased level of stress hormones, increased heart rate and blood pressure and impaired immune system,” Sorensen said.

Researchers analyzed participants’ medical and residential histories during an average 10-year period. A total of 1,881 suffered a stroke.

The researchers then measured their exposure to traffic sound over time using a noise calculation program designed to map noise levels in a variety of locations in Scandinavia for several years. The program takes into account a variety of factors that could amplify or blunt road noise, including traffic composition and speed, road surface and road type, nearby buildings and the position and heights of homes above the roads.

At the time the volunteers joined the study, 35 percent of them were exposed to noise levels greater than 60 decibels, and the majority (72 percent) lived at the same address throughout the study. Researchers estimated the lowest noise exposure to be 40 decibels and the highest to be 82 decibels.

They also accounted for a variety of other risk factors for stroke, such as air pollution, railway and aircraft noise, smoking, diet, alcohol and caffeine consumption.

The study is published in the current issue of the European Heart Journal.

The researchers “did a reasonable job of trying to control for other potential things that could affect the outcome,” said Dr. Larry B. Goldstein, director of the Duke Stroke Center at Duke University in Durham, N.C.

However, Goldstein noted that there are likely a number of additional factors that could not have been accounted for. “These epidemiological studies are always subject to a variety of unmeasured biases that could potentially affect the outcome,” he said.

For example, people living in areas with loud traffic noise are also likely have better access to fast food restaurants, and probably have a lower socioeconomic status than people in quieter suburban and rural areas, he noted. (The researchers also reported that a higher percentage of those exposed to noise over 60 decibels were from a lower income group, and since lower socioeconomic class is itself a predictor of stroke, they concluded they could not rule out the possibility that that skewed the results.)

“The other thing is, what do you do about it even if it’s true? Move to electric cars and no horns?” Goldstein added.

The researchers had an answer for that.

Sorensen said the study could be used to argue for construction methods that limit exposure to traffic noise, such as roads built with noise-reducing asphalt and noise barriers, or homes built with noise-isolating windows and other materials that dampen loud sounds.

SOURCES: Mette Sorensen, MSc, Ph.D., senior researcher, Institute of Cancer Epidemiology of Danish Cancer Society, Copenhagen, Denmark; Dr. Larry B. Goldstein, M.D., director, Duke Stroke Center, Duke University Health System; January 2011 European Heart Journal, online

Researchers are reporting major advances toward resolving two underlying problems involving Alzheimer’s disease: How do you know if someone who is demented has it? And how can you screen the general population to see who is at risk?

One study, reported in The New York Times in June, evaluated a new type of brain scan that can detect plaques that are uniquely characteristic of Alzheimer’s disease.

On Thursday, an advisory committee to the Food and Drug Administration, which requested the study, will review it and make a recommendation on whether to approve the test for marketing.

The second study asked whether a blood test could detect beta amyloid, the protein fragment that makes up Alzheimer’s plaque, and whether blood levels of beta amyloid were associated with a risk of memory problems. The answer was yes, but the test is not ready to be used for screening.

Both studies are to published in The Journal of the American Medical Association on Wednesday.

“These are two very important papers, and I don’t always say that,” said Neil S. Buckholtz, chief of the Dementias of Aging Branch of the National Institute on Aging.

The new brain scan involved a dye developed by Avid Radiopharmaceuticals, now owned by Eli Lilly. The dye attaches to plaque in patients’ brains, making it visible on PET scans.

The study by Avid involved 152 people nearing the end of life who agreed to have a brain scan and a brain autopsy after they died. The investigators wanted to know whether the scans would show the same plaques as the autopsies.

Twenty-nine of the patients in the study died and had brain autopsies. In 28 of them, the scan matched the autopsy results. Alzheimer’s had been diagnosed in half of the 29 patients; the others had received other diagnoses.

One subject who was thought to have had Alzheimer’s did not have plaques on the scans or on the autopsy — the diagnosis was incorrect. Two other patients with dementia turned out to have had Alzheimer’s although they had received diagnoses of other diseases.

The study also included 74 younger and healthier people who underwent the scans. They were not expected to have plaques, and in fact they did not.

If the F.D.A. approves the scan, medical experts said they would use it to help determine whether a patient with dementia had Alzheimer’s. If no plaques were found, they would have to consider other diagnoses.

The Avid scan will also be used — and is being used — by companies that are testing drugs to remove amyloid from the brain. The scans can show if the drugs are working. And a large study sponsored in part by the National Institute on Aging is scanning healthy people and following them to see if the scans predict the risk of developing Alzheimer’s disease.

The other study, on a blood test for Alzheimer’s, indicates that such a test may work. But researchers agree that it is not ready for clinical use.

The study, by Dr. Kristine Yaffe of the University of California, San Francisco, and the San Francisco Veterans Affairs Medical Center, included 997 subjects whose average age was 74 when the study began. They were followed for nine years and given memory tests and a blood test looking for beta amyloid.

By Gina Kolata

Heart disease is a killer. In fact, according to the Centers for Disease Control and Prevention, it is the leading cause of death in adults.

It is also largely preventable. A healthy diet and lifestyle are the best weapons you have to fight heart disease. Remember, it is the overall pattern of choices you make that counts.

Here are five ways you can keep your heart healthy:

1. Get to sleep: Harvard Medical School reports that not getting enough sleep can contribute to heart disease, and vice versa. Poor sleep can contribute to high blood pressure, heart attacks, stroke, obesity and diabetes. For quality sleep at night, exercise, eat a light, healthy snack several hours before bed, maintain a consistent bedtime routine, and practice relaxation techniques when you first lie down to keep your mind from racing.

2. Reduce stress: It is important to reduce stress and to learn how to de-stress if you want to avoid heart issues. Remember, you do not have to meet others’ expectations or demands. It’s OK to say “no.” To reduce stress, try aerobic exercise, which releases endorphins (natural substances that help you feel better and maintain a positive attitude); meditation; reading a book; writing in a journal; or joining a support group.

3. Watch what you eat: Choose lean meats and poultry without skin, and prepare them without added saturated and trans fat. Put the emphasis on fruits, vegetables, whole grains and low-fat sources of protein. Cut back on beverages and food with added sugar. If you drink alcohol, limit yourself to one drink a day if you’re a woman and two drinks per day if you’re a man.

4. Get busy: Daily physical activity is also important for avoiding heart disease. It is important to get 30 minutes of exercise per day, which can be broken up into three 10-minute segments. Find something you enjoy doing, such as taking a walk or riding a bike.

5. Manage your weight: Obesity is a risk factor for heart disease, and the extra weight makes your heart work even harder. Adopt healthy lifestyle choices on your own, which will lead to managing your weight over time, or speak to your doctor about options for weight reduction that are right for you.