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Int J Geriatr Psychiatry. 2004 Jun;19(6):575-81.

Critical Flicker Fusion Threshold in patients with Alzheimer's disease and vascular dementia.

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Ageing and Mental Health Research Group, School of Human and Health Sciences, University of Huddersfield, and Consultant in Old Age Psychiatry, South West Yorkshire Mental Health NHS Trust, Wakefield, UK.



Critical Flicker Fusion Threshold (CFFT) is a psychophysical threshold and in psychological terms is regarded as a measure of information processing capacity. The test has previously been shown to be a valid and reliable measure of CNS functioning in patients with Alzheimer's disease and may be a useful as a screening measure for the early detection of Alzheimer's disease (AD).


Consecutive referrals to the Wakefield Memory Clinic who met DSM-IV criteria for AD or vascular dementia (VaD) were invited to take part in the study. A range of neuropsychological tests and CFFT were administered to the two groups using standardised protocols and the ability of these various tests to distinguish between the two conditions was investigated.


Forty-six patients were included in the study. Of the various tests, only the descending component of CFFT and word fluency were significantly different in the two groups. In addition, the descending threshold had a sensitivity of 83% and a specificity of 69%.


CFFT could be useful as a screening instrument for early AD when combined with other measures and could facilitate the decision to commence antidementia treatment at an early stage. Further longitudinal work is needed to establish this.

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