A review of evidence for the claim that children are sleeping less than in the past

Study objectives: The notion that children are sleeping less than they used to is widespread. This study examined the strength of the evidence for this idea by tracing a "scholarly genealogy" of the claims presented within the literature.

Design: A systematic review of peer-reviewed literature was conducted to identify claims of a secular trend in children's sleep. For each identified claim, the references cited were reviewed.

Measurements and results: The review identified 51 studies. Of these, 17 evinced evidence (2 reported increases, 3 reported no change, 6 reported mixed trends, 6 reported decreases) and 34 provided statements without evidence. Although the evidence that sleep duration has declined is contested, all 34 studies reported a decline. Examination of the references cited revealed that 17 papers referred directly to studies which provided evidence, 4 papers referred indirectly to studies which provided evidence, 9 papers did not provide any evidence and 4 papers referred to studies which could not be located. Of the papers that did provide evidence, 85% referred to one of 3 sources of evidence, each of which was of moderate quality.

Conclusions: The genealogy of the notion of secular declines in children's sleep reveals a limited scientific basis. The apparent evidence base is inflated by repeated references to the same sources of evidence, reference to secondary sources, mis-referencing, and a failure to cite contrary evidence.