Can you say old-thymer?

Pronunciation of irregular words helps with dementia diagnosis

By Owen Dyer

Diagnosing dementia is hard enough in a patient who's been carefully monitored throughout their decline, but it can be impossible when the physician hadn't seen the patient before the onset of dementia. Not to put too fine a point on it, indeed, some patients experienced cognitive decline, but others were simply never that bright to begin with. How to tell the difference?

No valid diagnosis of dementia is possible without showing that mental abilities have deteriorated from a prior level. Until now, it's been almost out of the question to gauge an individual's level of pre-dementia cognitive functioning. But in a study published in the April 13 issue of Neurology, researchers from the University of Edinburgh, Scotland led by Ian Deary, PhD, claim to have used a straightforward reading test to estimate how well people functioned before they were affected by dementia.

The National Adult Reading Test (NART), requires people to pronounce words like ache and thyme that don't follow the usual rules of pronunciation. Higher scores are equated with sharper minds. Moreover, NART scores tend not to decline much with age, and basic reading skills are believed to hold up well in the early stages of dementia. These facts led the Edinburgh researchers to see whether NART scores in the elderly might accurately reflect earlier smarts.

"Our study posed two questions concerning the NART," noted the authors. "First, does mild to moderate dementia reduce NART scores? And second, do both non-demented and demented subjects show the same association between mental ability in youth and NART scores in old age?"

To answer these questions, they compared recent NART scores of 509 80-year-olds with IQ scores from their youth. At age 11, the subjects had taken an IQ-type test as part of the 1932 Scottish Mental Survey.

The researchers split up the 509 subjects into two groups: one group of 45 who'd been diagnosed with mild dementia and another group of 464 who hadn't. Those with dementia who scored lower on NART had lower childhood mental ability scores. After statistically controlling for childhood IQ, there was no difference in the correlation between NART scores and childhood ability test scores between the two groups.

"Our findings indicate that the National Adult Reading Test is a valid estimator of pre-onset cognitive ability in persons with mild to perhaps moderate dementia," conclude the authors. "The NART, at least in this sample, has passed a robust assessment of its validity as an estimator of pre-dementia cognitive ability. Our results show a constant relationship between NART and childhood ability in the context of very different levels of current cognitive status."

The Edinburgh team caution, however, that the relationship between NART scores and early childhood ability would probably not remain as steady in subjects with more severe dementia.