Washington ? More than 35 million people around the world are living with Alzheimer’s disease or other types of dementia, says the most in-depth attempt yet to assess the brain-destroying illness — and it’s an ominous forecast as the population grays.

The new count is about 10 percent higher than what scientists had predicted just a few years ago, because earlier research underestimated Alzheimer’s growing impact in developing countries.

Barring a medical breakthrough, the World Alzheimer Report projects dementia will nearly double every 20 years. By 2050, it will affect a staggering 115.4 million people, the report concludes.

“We are facing an emergency,” said Dr. Daisy Acosta, who heads Alzheimer’s Disease International, which released the report today.

The U.S. and other developed countries long have been bracing for Alzheimer’s to skyrocket. But the report aims to raise awareness of the threat in poorer countries, where finally people are living long enough to face what is mostly a disease of the 65-and-older population.

While age is the biggest driver of Alzheimer’s, some of the same factors that trigger heart disease — obesity, high cholesterol, diabetes — seem to increase the risk of dementia, too. Those are problems also on the rise in many developing countries.

Alzheimer’s Disease International — a nonprofit federation of more than 70 national groups — projects 35.6 million cases of dementia worldwide by 2010. That includes nearly 7 million people in Western Europe, nearly 7 million in South and Southeast Asia, about 5.5 million in China and East Asia and about 3 million in Latin America.

The report puts North America’s total at 4.4 million, although the Alzheimer’s Association of the U.S. uses a less conservative count to say more than 5 million people in this country alone are affected. The disease afflicts one in eight people 65 and older, and nearly one in two people over 85.

The report forecasts a more than doubling of dementia cases in parts of Asia and Latin America over the next 20 years, compared with a 40 percent to 60 percent jump in Europe and North America.