Is there an association between season of birth and reading disability?

Reported associations between season of birth and reading failure suggest medical causation and prevention. The relationship between season of birth and two measures of reading outcome in two cohorts of children (n1 = 2411 and n2 = 1972) was studied using chi2 tests. None was significant. Logistic regression was used to investigate the joint associations of gender, age at school entrance, and season of birth with reading outcome. A significant interaction between reading failure and age category (overage at school entrance vs correct age) by season of birth was observed. It was shown that this significant interaction was probably caused by kindergarten entrance cutoff birth dates. Although 67.8% of all overage children had summer births, only 15.3% failed in reading, which is not statistically different from the percentage of summer-born, correct-age low readers (13.6%). Results suggest that reported associations may be attributed to selective samples rather than the total population of school children who experience reading failure.