The Letter Digit Substitution Test: Normative Data for 1,858 Healthy Participants Aged 24–81 from the Maastricht Aging Study (MAAS): Influence of Age, Education, and Sex

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Abstract
The Letter Digit Substitution Test (LDST) is based on earlier developed substitution tests (e.g., Digit Symbol Substitution Test; Wechsler, 1955 Wechsler, D. 1955. Manual for the Wechsler Adult Intelligence Scale, New York: Psychological Corporation. [Google Scholar] , 1981 Wechsler, D. 1981. Manual for the Wechsler Adult Intelligence Scale-Revised, New York: Psychological Corporation. [Google Scholar] ) but uses over-learned signs instead of the symbols used in other substitution tests. The written and oral versions of the LDST were administered to a large, cognitively screened sample (N = 1,858) of adults aged 24 to 81 years. Age was the most important predictor of LDST performance, and females outperformed males. A low level of education profoundly influenced LDST performance: the effect of a low versus high level of education on LDST performance was comparable to about 20 years of aging. Regression-based normative data were prepared for both the written and oral versions of the LDST.