Intrasubject Variability of Sustained Attention Is Associated With Elevated Self-Reported Attention Deficits in Women With a Fragile X Premutation Allele

Objective: Women with a fragile X premutation (PM) self-report higher rates of attention difficulties than women without a PM; however, results of studies using objective measures of attention are inconsistent. The present study assessed whether intrasubject variability during a sustained attention task better predicted functional outcomes in women with a PM than the previously published standard reaction time and accuracy variables. Method: We analyzed continuous performance test, a computerized measure of sustained attention, and the Conners' Adult Attention-Deficit/Hyperactivity Disorder Rating Scale Report (CAARS) data from 273 women with a PM and 175 women without a PM aged 18-50 years. Separate analyses using Pearson correlations and independent t tests were performed on the full range of coefficient of variation (CV) of reaction time scores and the subset of scores that showed higher variability. Results: Performance variability of sustained attention measured by the continuous performance test was associated with functional outcomes measured by the CAARS in women with a PM but not women without a PM. Specifically, the CV in those with higher variability was correlated with two CAARS subscale scores (p = .006). Independent t tests showed significant differences in CV between CAARS scores dichotomized for the presence of subclinical symptoms for two subscales (p ≤ .001-.007). Correlation between the full range of CV scores and the CAARS Inattention/Memory Problems subscale approached significance (p = .012). Conclusions: Findings highlight the importance of including intrasubject variability in analyzing attention in clinical populations as a more sensitive objective measure associated with reported symptoms and to assist in predicting functional outcomes. Key Points Question: The present study observed whether performance variability on a computerized sustained attention task was a sensitive predictor of self-reported outcomes in women with a fragile X premutation (PM). Findings: Performance variability as measured by the coefficient of variation of reaction time of sustained attention was associated with functional outcome in women with a fragile X PM, while measures of standard reaction time and accuracy were not. Importance: Intrasubject variability is a valuable measure to include when analyzing attentional performance in clinical populations to bridge the gap between task performance and reported functioning and to assist in predicting function