Individuals with a neurodegenerative condition affecting language appear more likely to have had a history of learning disabilities than those with other types of dementia or with no cognitive problems, according to a report in the February issue of Archives of Neurology, one of the JAMA/Archives journals.
The condition known as primary progressive aphasia causes individuals to lose language abilities as they age, even though their other brain functions appear unaffected for at least the first two years, according to background information in the article. "Although risk factors for Alzheimer's disease have been well studied, much less is known about risk factors for primary progressive aphasia," the authors write.
Emily Rogalski, Ph.D., then at Northwestern University and now at Rush University Medical Center, Chicago, and colleagues studied a group of 699 individuals--108 with primary progressive aphasia, 154 with Alzheimer's disease, 84 with a related disorder known as frontotemporal dementia and 353 controls without dementia. When enrolling in the study, participants completed a detailed demographic and medical history interview that included two questions about whether they or immediate family members had a history of learning disabilities. A medical record review was conducted for the 23 individuals with primary progressive aphasia who reported either a personal or family history of learning disability.
Patients with primary progressive aphasia were more likely to have had learning disabilities or a close family member with learning disabilities than were those with other forms of dementia or without dementia. The review of patients with both aphasia and learning disabilities showed families with unusually high rates of learning problems, especially dyslexia. "For example, in three cases, nine of the 10 children of the probands [participants] were reported to have a history of specific learning disability in the area of language," the authors write.
"In our clinical practice, we encounter many patients with primary progressive aphasia who report that spelling was never their 'strong suit' or that they could not learn new languages, but who would not have identified themselves as having a learning disability," they continue. The findings may, therefore, underestimate the frequency of learning disabilities in patients and their families.
The association suggests that some individuals or families may have an underlying susceptibility to difficulties with the language network. "This relationship may exist in only a small subgroup of persons with dyslexia without necessarily implying that the entire population with dyslexia or their family members are at higher risk of primary progressive aphasia," the authors conclude.
(Arch Neurol. 2008;65:244-248. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: This study was supported by the National Institute on Aging, by an Alzheimer's Disease Core Center grant and by a grant from the National Institute on Deafness and Other Communication Disorders. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.