Specific Learning Disorder: Prevalence and Gender Differences

Abstract

Comprehensive models of learning disorders have to consider both isolated learning disorders that affect one learning domain only, as well as comorbidity between learning disorders. However, empirical evidence on comorbidity rates including all three learning disorders as defined by DSM-5 (deficits in reading, writing, and mathematics) is scarce. The current study assessed prevalence rates and gender ratios for isolated as well as comorbid learning disorders in a representative sample of 1633 German speaking children in 3rd and 4th Grade. Prevalence rates were analysed for isolated as well as combined learning disorders and for different deficit criteria, including a criterion for normal performance. Comorbid learning disorders occurred as frequently as isolated learning disorders, even when stricter cutoff criteria were applied. The relative proportion of isolated and combined disorders did not change when including a criterion for normal performance. Reading and spelling deficits differed with respect to their association with arithmetic problems: Deficits in arithmetic co-occurred more often with deficits in spelling than with deficits in reading. In addition, comorbidity rates for arithmetic and reading decreased when applying stricter deficit criteria, but stayed high for arithmetic and spelling irrespective of the chosen deficit criterion. These findings suggest that the processes underlying the relationship between arithmetic and reading might differ from those underlying the relationship between arithmetic and spelling. With respect to gender ratios, more boys than girls showed spelling deficits, while more girls were impaired in arithmetic. No gender differences were observed for isolated reading problems and for the combination of all three learning disorders. Implications of these findings for assessment and intervention of learning disorders are discussed.

The precursors of double dissociation between reading and spelling in a transparent orthography

“…These findings are in line with those of previous studies (e.g., Furnes & Samuelsson, 2011;Moll et al, 2014;Wimmer & Mayringer, 2002). Despite the shortlived importance of phonological awareness as a predictor of reading in Finnish (e.g., Silvén, Poskiparta, Niemi, & Voeten, 2007;Torppa et al, 2015) and in other transparent orthographies (e.g., Georgiou, Parrila, & Papadopoulos, 2008;Mann & Wimmer, 2002), it has been shown to be an important predictor of spelling (e.g., Babayiğit & Stainthorp, 2010;Caravolas et al, 2012;Furnes & Samuelsson, 2011).…”

“…Landerl and Wimmer (2008) further argued that children with phonological deficits might not be able to establish such associations. This seems to be in line with the findings of studies with unselected samples of German-speaking children showing that phonological awareness and phonological short-term memory are significant predictors of spelling, but not of reading fluency (e.g., Landerl & Wimmer, 2008;Mann & Wimmer, 2002;Mayringer, Wimmer, & Landerl, 1998;Moll et al, 2014). However, working with a group of third-and fourth-grade German-speaking children, Moll and Landerl (2009) failed to find differences between good readers/poor spellers and good readers/good spellers in phonological awareness.…”

“…If the cognitive basis of reading and spelling deficits differs, the kindergarten cognitive profiles of the deficit groups might differ as well. Because reading in our study was operationalized with reading fluency measures (due to lack of variability in reading accuracy measures in Finnish) and spelling with an accuracy measure, we expected that slow reading would be associated with slow RAN (e.g., de Jong & van der Leij, 2002;Eklund et al, 2013;Georgiou et al, 2011;Landerl et al, 2013;Wimmer et al, 1998) and inaccurate spelling would be associated with phonological problems (e.g., Furnes & Samuelsson, 2011;Landerl & Wimmer, 2008;Mayringer et al, 1998;Moll et al, 2014;Niolaki, Masterson, & Terzopoulos, 2013). Second, letter knowledge in kindergarten has been found to be a key predictor of reading and spelling skills (e.g., Kirby, Parrila, & Pfeiffer, 2003;Leppänen, Niemi, Aunola, & Nurmi, 2004;Lerkkanen, Rasku-Puttonen, Aunola, & Nurmi, 2004;Schatschneider, Fletcher, Francis, Carlson, & Foorman, 2004), and in the present study the role of letter knowledge is for the first time examined with respect to unexpected reading and spelling deficits.…”

“…However, the imperfect correlation between the two (rs range from .60 to .80; see meta-analysis by Swanson, Trainin, Necoechea, & Hammill, 2003) leaves open the window for a dissociation in which good readers can also be poor spellers (known as unexpected poor spellers) and poor readers can also be good spellers (known as unexpected poor readers). A few large-scale studies have indeed shown that these two performance profiles are not rare and may each affect 3-7% of school-age children (Fayol, Zorman, & Lété, 2009;Moll, Kunze, Neuhoff, Bruder, & Schulte-Körne, 2014;Moll & Landerl, 2009;Wimmer & Mayringer, 2002).…”

ATP2C2andDYX1C1are putative modulators of dyslexia‐related MMR

“…Dyslexia has a prevalence of 5% among German‐speaking individuals (Moll, Kunze, Neuhoff, Bruder, & Schulte‐Körne, 2014). The heritability was estimated at 50%–70% (de Kovel et al., 2004; Harlaar, Spinath, Dale, & Plomin, 2005; Shaywitz et al., 1998), but only a small proportion of the genetic basis of dyslexia has been uncovered.…”