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Longitudinal analysis of sleep in relation to BMI and body fat in children: the FLAME study

BMJ 2011; 342 doi: (Published 26 May 2011) Cite this as: BMJ 2011;342:d2712
  1. Philippa J Carter, doctoral student1,
  2. Barry J Taylor, professor, head of department1,
  3. Sheila M Williams, research associate professor, biostatistician2,
  4. Rachael W Taylor, Karitane research associate professor in early childhood obesity3
  1. 1Department of Women’s and Children’s Health, University of Otago, Dunedin, New Zealand
  2. 2Department of Preventive and Social Medicine, University of Otago
  3. 3Edgar National Centre for Diabetes and Obesity Research, Department of Medical and Surgical Sciences, University of Otago
  1. Correspondence: R Taylor, Department of Human Nutrition, PO Box 56, Dunedin 9054, New Zealand rachael.taylor{at}
  • Accepted 17 March 2011


Objectives To determine whether reduced sleep is associated with differences in body composition and the risk of becoming overweight in young children.

Design Longitudinal study with repeated annual measurements.

Setting Dunedin, New Zealand.

Participants 244 children recruited from a birth cohort and followed from age 3 to 7.

Main outcome measures Body mass index (BMI), fat mass (kg), and fat free mass (kg) measured with bioelectrical impedance; dual energy x ray absorptiometry; physical activity and sleep duration measured with accelerometry; dietary intake (fruit and vegetables, non-core foods), television viewing, and family factors (maternal BMI and education, birth weight, smoking during pregnancy) measured with questionnaire.

Results After adjustment for multiple confounders, each additional hour of sleep at ages 3-5 was associated with a reduction in BMI of 0.48 (95% confidence interval 0.01 to 0.96) and a reduced risk of being overweight (BMI ≥85th centile) of 0.39 (0.24 to 0.63) at age 7. Further adjustment for BMI at age 3 strengthened these relations. These differences in BMI were explained by differences in fat mass index (−0.43, −0.82 to −0.03) more than by differences in fat free mass index (−0.21, −0.41 to −0.00).

Conclusions Young children who do not get enough sleep are at increased risk of becoming overweight, even after adjustment for initial weight status and multiple confounding factors. This weight gain is a result of increased fat deposition in both sexes rather than additional accumulation of fat free mass.


  • Contributors: PJC was involved in initial design of the longitudinal study, undertook the data collection, completed all accelerometry analyses, produced the initial methods section of the paper, and revised the draft paper. BJT was the principal investigator of the project and was responsible for study design, monitoring of data collection, and revision of the draft paper. SWM contributed to study design, designed and completed all statistical analyses, and revised the draft paper. RWT conceived the idea for this paper, was involved in study design, monitored data collection, drafted and revised the paper, and is guarantor.

  • Funding: This study was funded by the University of Otago, the Child Health Research Foundation, the New Zealand Heart Foundation, and the Dean’s Bequest-AAW Jones Trust. The funders had no role in study design; or in the collection, analysis, and interpretation of data; or in the writing of the report or the decision to submit the article for publication.

  • Competing interests: All authors have completed the Unified Competing Interest form at (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: The study was approved by the Lower South regional ethics committee (Reference OTA/04/03/023) and signed informed consent was obtained from the parents or guardians of each participating child.

  • Data sharing: No additional data available.

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