The verbal fluency index: Dutch normative data for cognitive testing in ALS

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neurology

Background:

• Executive dysfunction affects 30-50% of amyotrophic lateral sclerosis (ALS) patients.
• The verbal fluency index (VFI) assesses cognitive function by measuring average thinking time per word, correcting for speech slowness.
• Current use of VFI as a cognitive impairment marker is limited by a lack of valid norm scores.

Purpose of the Study:

• To establish normative data for the spoken verbal fluency index (VFI) in the Dutch amyotrophic lateral sclerosis (ALS) population.
• To enable more accurate cognitive impairment assessment in ALS patients using the VFI.
• To provide a basis for international validation of VFI norms.

Main Methods:

• 273 Dutch volunteers, demographically matched to the ALS population, completed one-minute and three-minute spoken letter fluency tests.
• Stepwise linear regression analyzed the impact of demographic variables, medical history, and medication on VFI performance.
• Formulas for standardized z-scores, adjusted for educational level, were derived for the VFI.

Main Results:

• Educational level showed a significant negative correlation with both one-minute and three-minute VFI scores (r = -0.3 and r = -0.4, p < 0.001).
• No significant correlations were found between VFI performance and age, gender, medication, or past medical history.
• Standardized z-score formulas for the VFI, corrected for educational level, were calculated.

Conclusions:

• This study presents the first Dutch normative data for the spoken verbal fluency index (VFI), applicable for international use with recommended validation in other languages.
• The findings underscore the necessity of disease-specific norm scores for time-dependent cognitive tests like the VFI in amyotrophic lateral sclerosis (ALS).
• Accurate cognitive assessment in ALS is improved by these VFI normative data, aiding clinical practice and research.