THURSDAY, June 20 (HealthDay News) -- Black and Hispanic Americans have a greater age-related decrease in their sense of smell than whites, a new study says.

Losing the ability to smell can lead to poor nutrition because food smells play a major role in how foods taste, the researchers noted. A declining sense of smell may also be an early warning sign of degenerative brain diseases such as Alzheimer's or Parkinson's, and can be associated with an increased risk of early death.

About 24 percent of Americans aged 55 and older have a measurable problem with their sense of smell, according to the U.S. National Institute on Aging. That rises to about 30 percent for those aged 70 to 80 and more than 60 percent for those over age 80.

The new study included more than 3,000 older adults who were asked to identify five common odors. Only about half (49 percent) correctly identified all five odors, 78 percent got four or more right, 92 percent identified at least three, and 97 percent got two or more correct.

The ability to identify the odors declined with age. All five odors were identified by 64 percent of participants aged 57, but only 25 percent of those aged 85. Women did better than men, with scores equivalent to being five years younger, the investigators found.

In addition, non-white participants consistently scored 47 percent lower than whites, equivalent to a nine-year increase in age, according to the study published online recently in the Journal of Gerontology: Medical Sciences.

"We have long known that men begin to lose their sense of smell some years sooner than women, but this is the first study to point to racial or ethnic differences," study author Dr. Jayant Pinto, an associate professor of surgery at the University of Chicago, said in university news release. "What surprised us was the magnitude of the difference. The racial disparity was almost twice as large as the well-documented difference between men and women."

The cause of this racial/ethnic difference was unclear. Genetics could be a factor, as could exposure to nerve-damaging substances in the environment, or both, the researchers pointed out.

They explained that people's race/ethnicity may lead to different life experiences and environmental exposures that may interact with biological differences to affect age-related sensory loss.

More information

The U.S. National Institute on Aging has more about loss of sense of smell.