Berlin ? The likelihood of being admitted to hospital or dying with atrial fibrillation, a life-threatening chaotic heartbeat common among the elderly, increases dramatically during winter months, new research indicates.

A study found that among people aged 75 to 84, hospital admissions for atrial fibrillation were 25 percent higher than average in the winter, and nearly 40 percent higher than normal for those 85 and older.

The study, presented this week at a meeting of the European Society of Cardiology, also found that deaths from the condition were higher in winter.

The doctors’ advice: stay warm, get a flu shot and stay sober.

The disorder affects people of all ages, but is particularly common among the elderly. It afflicts about 10 percent of people older than 75, including 2 million in the United States.

With an aging population and a greater proportion of people surviving heart attacks, experts predict that the number of cases of atrial fibrillation is likely to increase in the next decade.

“Given the almost universal problem of peak winter demands on hospitals in almost all countries with variable climatic conditions and the likelihood of an epidemic of atrial fibrillation in the near future, these represent significant findings,” said Dr. Simon Stewart, the study’s lead investigator.

“It is possible, for example, that greater efforts can be made to warn high-risk patients of the dangers of inadequate heating and clothing, the need for flu vaccinations and the need to limit alcohol intake,” said Stewart, a professor of cardiology at the Queen Elizabeth Hospital in Adelaide, Australia.

“As atrial fibrillation is often a precursor to stroke and heart failure two of the most costly, deadly and disabling of diseases the potential to save lives, and money, is enormous,” he said.

Researchers have already determined that heart attacks, heart failure and heart-related sudden deaths are more common in winter.

Although experts were not surprised at the findings, they said the study is the first to document a seasonal influence on chaotic heart rhythm.

“That is the time for flu and pneumonia and we know …. that may be a cause of atrial fibrillation,” said Dr. Jean-Yves Le Heuzey, an atrial fibrillation specialist at the Pierre and Marie Curie University in Paris.

Atrial fibrillation occurs when the two small upper chambers of the heart (the atria) quiver instead of beating effectively. Blood isn’t pumped completely out of them, so it may pool and clot. Clots that travel to the brain can cause strokes.

The disturbances can last anywhere from a few seconds to a lifetime.

About 15 percent of strokes occur in people with atrial fibrillation, according to the American Heart Assn.