The Digit Span Test: Normative Data for the Iranian Normal Population

Background: The digit span test (DST) is one of the most widely used neuropsychological tools to measure two neurocognitive functions of working memory and attention. Objectives: This study aimed to collect Iranian normative data on DST and examine the association between three demographic variables and performance in DST. Materials Methods: As part of the Iranian brain imaging database (IBID) project, the present study was conducted in 2017-2018 on three hundred normal people aged 20 to 70. They were recruited using convenience sampling in Tehran City, Iran. Each decade consisted of 60 participants, and the gender proportion was equal. Five decades of age, gender and education were the independent variables. The dependent variables were DST scores (the longest digit sequence and total digit span). Results: Age and education had a significant negative and positive correlation with both subtests (P=0.01), respectively; however, no significant correlation was observed between gender and DST scores (P 0.05). According to multivariate analysis of variance, the interaction of age, gender and education did not lead to a significant difference in the DST scores (P=0.309). In addition, The Tukey post hoc test showed that participants under 40 had significantly higher DST scores than older participants (P 0.05).  Conclusion: The demographic variables have a significant association with the working memory and attention performance of the normal Iranian population, and it is necessary to interpret DST scores using regional normative data.