Early development in Rett syndrome - the benefits and difficulties of a birth cohort approach.
Peter B Marschik, Sanne Lemcke, Christa Einspieler and 4 others
PMID 28534656WHAT IT FOUND
In this large birth cohort, girls later diagnosed with Rett syndrome showed few developmental differences from the general population at 6 months.
By 18 months, all six had clear gross motor delays, such as inability to walk without support, while speech and social milestones lagged similarly to many typical peers.
Key findings
01At 6 months, developmental differences between girls later diagnosed with Rett syndrome and the general cohort were minimal, with only a slight delay in sitting without support.
02By 18 months, none of the six girls with Rett syndrome could walk without support, climb stairs with support, or take off socks, whereas the vast majority of the general cohort had achieved these motor milestones.
03Speech and social milestones at 18 months, such as having a vocabulary of more than 10 words, were not achieved by the Rett group, but a large proportion of the general cohort also had not achieved these milestones by that age.
STILL TO COME
How it was doneWhat they foundWhat it means for PTsWhat it means for OTsWhat it means for SLPs
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What it does not show
The sample size of girls with Rett syndrome was extremely small (n=6), making the results descriptive rather than statistically robust. The data collection was quasi-prospective, with some information collected retrospectively (e.g., parents recalling the age of sitting or walking at the 18-month interview), which introduces potential memory bias. The original cohort interviews were not designed to detect specific rare disorders or peculiarities in early development, limiting the sensitivity of the questions. Some girls were already diagnosed with Rett syndrome by the age of 18 months, which may have influenced how parents answered developmental questions.
Declared interests
The Danish National Birth Cohort was initiated by the Danish National Research Foundation and received grants from the Pharmacy Foundation, Egmont Foundation, March of Dimes Birth Defects Foundation, Augustinus Foundation, and Health Insurance Foundation. Author PBM was supported by FWF 19581, 25241 and the Franz Lanyar Foundation. Sanne Lemcke was supported by the Tryg Foundation.
The easy way to misread this
Do not interpret the lack of speech and social milestones at 18 months as a unique early sign of Rett syndrome. The study shows that a large proportion of the general cohort also had not achieved these milestones by that age. The most distinct early differences were in gross motor skills, such as walking and climbing stairs.