Colorado reading project: Longitudinal analyses

Extensive psychometric test data were obtained from two independent samples of reading-disabled and control children: 70 probands and 75 controls tested on two occasions over an average interval of 4.2 years, and 35 probands and 22 controls tested on three occasions over an average interval of 8.6 years. When composite measures of reading performance and symbol-processing speed were subjected to mixed-model multivariate analyses of variance, significant effects due to group (reading-disabled versus control) and time (i.e., test session) were obtained in both samples, and a significant group-by-time interaction was obtained for the sample tested on three occasions. In general, rates of change in reading performance are highly similar for reading-disabled and control children. However, with regard to symbol-processing speed, differences between the two groups increase as a function of age. Although no evidence was obtained for differential longitudinal stability of either composite measure in reading-disabled and control children, results of a multiple regression analysis suggest that reading deficits during middle childhood are highly predictive of later reading problems, even into early adulthood.