The researchers say their findings indicate that people around 100 years old may see life differently than people 20 or 40 years their junior and traditional tests for depression may not be effective in the extremely old.

"We're saying look at more of the components that make up depression," said Peter Martin, a gerontology researcher at Iowa State University and one of the study's authors. "Some may be more relevant to centenarians than others."

Martin and his fellow researchers examined existing information collected from 323 people living in Georgia between 1988 and 1997 who were over 60, 80 or 100 years old. Of these, 139 participants were over 100 years old, 93 were in their 80s and 91 were in their 60s.

Each of the study's participants answered a survey known as the Geriatric Depression Scale, which asks 30 yes-or-no questions about whether the person was depressed in the past week. The more yeses, the more likely they're depressed.

Overall, the100-year-olds scored higher for depression than the people in their 80s or 60s according to the survey's summary score of all 30 questions.

The centenarians answered "yes" to about 13 questions on the survey while people in their 80s answered "yes" to about 12 and people in their 60s said "yes" to about 11 questions.

All of the 100-year-olds, however, said they were in "good spirits."

Indeed, when the researchers looked at subsets of questions, they found the participants in their 60s and 80s said yes more often to statements like, "I feel downhearted," "I am not satisfied with life," "I am afraid of something bad," and "I do not enjoy getting up in the morning."

"If you look (just) at the summary score you might come to the wrong conclusion," Martin told Reuters Health.

Even though the survey was developed for geriatric subjects, he says, some of the questions may yield misleading answers when it comes to the oldest old.

Some of the "yes" answers on the scale could be chalked up to the 100-year-olds' advanced age -- especially those relating to being less active, being unable to start new projects or saying they had lost interest or energy.

Other than physical impairments and limitations, Martin said, there are differences in other symptoms when you compare younger people to those who are over 100 years old.

"You know a centenarian is probably going to tell you, 'I'm not going to live much longer,'" said Martin. But he added, while that statement may sound disturbing coming from a younger person, it's reality for someone over 100 years old.

Instead, Martin said, a 100-year-old saying they feel sad or "blue" may be a better sign of depression.

"Depression varies in both its appearance and experience across the lifespan," said Dr. Charles F. Reynolds III, the endowed professor in geriatric psychiatry at the University of Pittsburg Medical Center.

Reynolds, who was not involved with the new study, told Reuters Health that in diagnosing depression, it's typical to combine the use of self reporting, like a survey, with an interview of the person, their family or someone involved with their care.

The researchers write in the Journal of the American Geriatrics Society that the study is limited because it focused on people still living in a community. So the results may not be applicable to someone living in a nursing home or other institution.

Martin told Reuters Health that treatment for depression in a very old person can include medication, but he said it could be as simple as allowing the person to contribute or be more engaged.

"Their life is not over yet. It's the last chapter of the book, but sometimes the last chapter of the book has the most interesting stuff in it," said Martin.

SOURCE: bit.ly/AfLdBd Journal of the American Geriatrics Society, online January 27, 2012.

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