Ni Mhurchu et al. BMC Public Health 2010, 10:738 http://www.biomedcentral.com/1471-2458/10/738 sustainability. School and parent evaluations will be under- taken at the end of the study using standardised question- naires. Evaluation of breakfast provider perspectives will be undertaken via semi-structured interviews on comple- tion of the trial. Statistical analysis Treatment evaluations will be performed according to the principle of intention-to-treat (ITT), using data collected from individual trial participants at randomised schools. Schools will be treated as clusters in the analysis because participant data collected from the same school are likely to be more correlated than those collected from different schools. Furthermore, in a stepped wedge design, informa- tion is collected repeatedly on each participant over the control and intervention periods. Advanced statistical methods appropriate for this type of study design will therefore be used. Generalised Linear Mixed models will be used to adjust for the effect of clustering and repeated measures over time. Intra cluster correlation (ICC) coeffi- cients will be re-evaluated using the study data. Unidirec- tional crossover as well as any potential secular trends may be incorporated with a time effect. A pre-specified analysis plan outlines detailed statistical methods. Discussion The breakfast intervention trial described in this paper is the first of its kind in Australasia and amongst only a very small number conducted in high income countries to date. Whilst evidence suggests that school breakfast programmes have beneficial effects on student atten- dance, school grades, and psychosocial function, findings to date have been inconsistent and limited by poor study methodology. This study addresses many of the shortfalls in current research into the effects of school breakfast programmes by employing a prospective cluster rando- mised trial design to minimise confounding and bias, thus substantially increasing confidence in findings. Results from this research will provide valuable, much needed information on the effects of free school breakfast programmes in high income countries on school atten- dance, achievement, psychosocial function, and nutrition. Furthermore this trial provides an excellent example of the feasibility and value of the stepped wedge trial design in evaluation of pragmatic public health interventions. All too often such initiatives do not undergo robust eva- luation due to difficulties in aligning the implementation timetable and rollout strategy with trial design and recruitment [32]. This trial provides a useful illustration of simultaneous implementation and rigorous evaluation of a public health intervention programme. Page 5 of 6 Acknowledgements The study is funded by the Health Research Council of New Zealand (09/ 337). Cliona Ni Mhurchu holds the National Heart Foundation Senior Fellowship (Grant 1380). We wish to thank the schools, children and families taking part in the study, and the providers of the breakfast programmes: the New Zealand Red Cross, Progressive Enterprises (Countdown supermarkets), Fonterra Cooperative Group Limited, and Sanitarium Health Food Company. We are grateful for the input and assistance of our steering committee members (Sara Williams, Kate Kember, Christine McKerchar, Leonie Matoe), research assistants (Denise Miller, Oliver Allen), data manager (Vanessa Singh), data analyst (Joy Jiang), and CTRU IT and operations staff. Author details 1Clinical Trials Research Unit, School of Population Health, Faculty of Medicine & Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. 2Teaching, Learning and Development, Faculty of Education, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. Authors’ contributions Principal responsibility for study design was assumed by DG, YJ, RM and CNM. DG, JM and MT developed the study protocol and materials. JH had substantial input into study design and oversight. JM is responsible for day- to-day study management. YJ is responsible for all aspects of statistical design and analysis. CNM drafted the study manuscript integrating substantial written contributions from MT. All authors contributed to and approved the final manuscript. Competing interests The authors declare that they have no competing interests. Received: 21 November 2010 Accepted: 29 November 2010 Published: 29 November 2010 References 1. Adolescent Health Research Group: A health profile of New Zealand youth who attend secondary school. New Zealand Medical Journal 2003, 116(1171):U380. 2. Ministry of Health: A Portrait of Health: Key Results of the 2006/07 New Zealand Health Survey Wellington: Ministry of Health; 2008. 3. Utter J, Scragg R, Mhurchu CN, Schaaf D: At-home breakfast consumption among New Zealand children: associations with body mass index and related nutrition behaviors. Journal of the American Dietetic Association 2007, 107(4):570-576. 4. Rampersaud G, Pereira M, Girard B, Adams J, Metzl J: Breakfast habits, nutritional status, body weight and academic performance in children and adolescents. Journal of the American Dietetic Association 2005, 105:743-760. 5. Pollitt E, Matthews R: Breakfast and cognition: an integrative summary. American Journal of Clinical Nutrition 1998, 67(suppl):804S-813S. 6. Grantham-McGregor SM: Can the provision of breakfast benefit school performance? Food and Nutrition Bulletin 2005, 26(2):S144-S158. 7. Hoyland A, Dye L, Lawton CL: A systematic review of the effect of breakfast on the cognitive performance of children and adolescents. Nutrition Research Reviews 2009, 22:220-243. 8. Sandercock GRH, Voss C, Dye L: Associations between habitual school-day breakfast consumption, body mass index, physical activity and cardiorespiratory fitness in English schoolchildren. European Journal of Clinical Nutrition 2010, 64:1086-1092. 9. Wilson N, Parnell W, Wohlers M, Shirley P: Eating breakfast and its impact on children’s daily diet. Nutrition & Dietetics 2006, 63:15-20. 10. Read M: Malnutrition, hunger, and behavior. II. Hunger, school feeding programs, and behavior. Journal of American Dietetic Association 1973, 63(4):386-391. 11. Scrimshaw N: Malnutrition, brain development, learning and behaviour. Nutrition Research 1998, 18(2):351-379.