Special Communication
April 28, 2004

Sex Differences in Developmental Reading DisabilityNew Findings From 4 Epidemiological Studies

Author Affiliations

Author Affiliations: Social, Genetic and Developmental Psychiatry Centre (Drs Rutter, Caspi, Maughan, and Moffitt) and Department of Child and Adolescent Psychiatry (Dr Goodman), Institute of Psychiatry, King's College, London, England; Christchurch School of Medicine, Christchurch, New Zealand (Dr Fergusson and Mr Horwood); Office for National Statistics, London, England (Dr Meltzer); and University of Warwick, Coventry, England (Dr Carroll).

JAMA. 2004;291(16):2007-2012. doi:10.1001/jama.291.16.2007

Context An influential article published in 1990 claimed that the increased rate of reading disability in boys was a consequence of referral bias.

Objectives To summarize the history of research on sex differences in reading disability and to provide new evidence from 4 independent epidemiological studies about the nature, extent, and significance of sex differences in reading disability.

Design, Setting, and Participants The Dunedin Multidisciplinary Health and Development Study comprised 989 individuals (52.1% male) in a cohort born between April 1972 and March 1973 in Dunedin, New Zealand, and followed up from age 3 years; reading performance and IQ were assessed at ages 7, 9, and 11 years using the Burt Word Reading Test and the Wechsler Intelligence Scale for Children–Revised (WISC-R), respectively. The Christchurch Health and Development Study comprised 895 individuals (50% male) in a prospectively studied cohort born in the Christchurch, New Zealand, region during a 4-month period in 1977; reading performance and IQ were assessed at ages 8 to 10 years using the Burt Word Reading Test and the WISC-R. The Office for National Statistics (ONS) Study comprised a UK nationally representative sample of 5752 children (50.1% male) aged 9 to 15 years in 1999; reading was assessed on the British Ability Scales II and IQ on the British Picture Vocabulary Scales II. The Environmental Risk Longitudinal Twin Study (E-Risk) comprised 2163 twin children from England and Wales (49.1% male) identified at birth in 1994 and 1995 and included administration of the Test of Word Reading Efficiency at age 7 years and the Wechsler Preschool and Primary Scale of Intelligence–Revised as a test of IQ at age 5 years.

Main Outcome Measure Reading performance by sex in the lowest 15% of the distribution for all 4 studies, with and without taking IQ into account.

Results In all 4 studies, the rates of reading disability were significantly higher in boys. For non–IQ-referenced reading disability: Dunedin study, 21.6% in boys vs 7.9% in girls (odds ratio [OR], 3.19; 95% confidence interval [CI], 2.15-4.17); Christchurch study, 20.6% in boys vs 9.8% in girls (OR, 2.38; 95% CI, 1.62-3.50); ONS study, 17.6% in boys vs 13.0% in girls (OR, 1.43; 95% CI, 1.23-1.65); and E-Risk, 18.0% in boys vs 13.0% in girls (OR, 1.39; 95% CI, 1.04-1.86). The rates for IQ-referenced reading disabilities were similar.

Conclusion Reading disabilities are clearly more frequent in boys than in girls.