RESEARCH ARTICLE Longitudinal Study of Performance on the Ruff Figural Fluency Test in Persons Aged 35 Years or Older

The Ruff Figural Fluency Test (RFFT) is a cognitive test tomeasure executive function. Lon-gitudinal studies have shown thatrepeated testing improves performance on the RFFT. Such a practice effect may hinder the interpretation of test results in a clinical setting. There-fore, we investigated the longitudinal performance on the RFFT in persons aged 35–82 years. Performance on the RFFT was measured three times over an average follow-up peri-od of six years in 2,515 participants of the Prevention of REnal and Vascular ENd-stage Dis-ease (PREVEND) study in Groningen, the Netherlands: 53%men; mean age (SD), 53 (10) years. The effect of consecutive measurements on performance on the RFFT was investi-gated with linear multilevel regression models that also included age, gender, educational level and the interaction term consecutive measurement number x age as independent vari-ables. It was found that the mean (SD) number of unique designs on the RFFT increased from 73 (26) at the first measurement to 79 (27) at the second measurement and to 83 (26) at the third measurement (p<0.001). However, the increase per consecutive measurement number was negatively associated with age and decreased with 0.23 per one-year incre