Skipping breakfast has been linked to reductions in cognition and academic performance [1–3], resulting in strong arguments for public health interventions to increase breakfast consumption. However, well-designed randomized controlled trials (RCTs) [4–6] do not provide convincing evidence of benefit to support the substantial costs of school breakfast programs.

Experimental evidence indicates that, on any given day, skipping breakfast lowers cognitive and academic performance [3]. A systematic review, published in 2009, included 45 studies that examined the association between skipping breakfast and cognitive performance, including memory, attention and test grades. The review focused on school-aged children but the age of participants ranged from 3 years to a mean age of 21 years. The authors concluded that eating breakfast generally had a positive effect on cognitive performance [2]. The beneficial effects of eating breakfast were stronger when testing occurred later in the morning, when tests were more demanding and error rate was considered, and in malnourished populations [2]. In most studies, cognitive performance was assessed within 12 h of eating/skipping breakfast [2].

The long-term effects of skipping breakfast are less clear. A 2013 review examined the association between skipping breakfast and classroom behavior or academic performance (school grades or standardized achievement tests) among children and adolescents (aged 5 to 19 years) [1]. Five of the eight studies that examined habitual breakfast consumption reported a beneficial association with academic performance. Only one study used a longitudinal design [7], involving 21,400 5-year old USA children followed for 10 years. In contrast to the cross-sectional studies, frequency of breakfast consumption was not significantly associated with standardized test scores for reading, mathematics and science or teacher-reported behavior after adjusting for a wide range of potential confounders [7]. However, breakfast was defined as eating breakfast with the family, so children who ate breakfast alone or at school would be misclassified as breakfast skippers.

School breakfast programs are being implemented to increase breakfast consumption. Despite their popularity, there is little evidence to support their effectiveness. Three well-designed trials found programs that made school breakfast available to all children, did not improve academic achievement or classroom behavior among elementary school children (aged 4-14 years) [4–6]. However, none of the trials increased breakfast consumption among children who normally skipped breakfast; instead, children who usually ate breakfast at home ate it at school.

RCTs are the gold standard for determining causation but pose substantial challenges in this field. Most cross-sectional studies did not control for socioeconomic status (SES) [1], which is an important predictor of both academic performance [8] and breakfast consumption [9, 10]. Data examining the long-term effect of breakfast consumption on academic performance are sparse. Using data from a national study of Australian children, this study examines whether skipping breakfast at age 8-9 years predicts poorer academic performance and classroom behavior 2 years later. We hypothesize that breakfast skippers will have poorer school performance and classroom behavior than those who eat breakfast.

Children were recruited for Growing up in Australia: the Longitudinal Study of Australian Children (LSAC) during 2004, aged 4-5 years (Wave 1, N = 4983). The sampling frame was extracted from the enrolment database of Medicare, the national health care scheme in Australia that enrolls 98% of Australian residents by 1 year of age [11]. The children were selected using a two-stage design [11]. In the first stage, postcodes were stratified by state/territory and urban/rural location to ensure geographical representation. Very remote postcodes were excluded. Postcodes were then randomly selected. In the second stage, a 10% sample of children born between March 1999 and February 2000 were randomly selected. For each postcode, children were listed according to date of birth, and a systematic random sample was taken from this list to ensure a representative range of birth dates.

The response rate at baseline was 54% (N = 4983). Data are collected biennially, with a core face-to-face home visit supplemented by a range of additional measures and data linkages. Data used in this analysis were collected via three mechanisms: home-based face-to-face interview and two subsequent written questionnaires completed by a parent/caregiver at wave 3 (2008); questionnaires completed by teachers at wave 3 (2008) and wave 4 (2010); and linked data from the Australian National Assessment Program - Literacy And Numeracy (NAPLAN), the national standardized school assessment program (Additional file 1: Figure S1). The children were 8-9 years old at wave 3 (participation rate 87% of wave 1) and 10-11 years at wave 4 (participation rate 84% of wave 1, Fig. 1).

The analysis of confidentialized LSAC data had the approval of the Australian Institute of Family Studies ethic committee. Consent to participate in the study was given by a parent at wave 1 and permission to link with the child’s NAPLAN results at wave 3 (or wave 4, if the child did not participate in wave 3).

Of the 4331 eligible children, 2280 were included in the main analysis (Fig. 1). About one quarter of the children completed the Year 5 NAPLAN tests in 2009 (n = 500, 23.0% of the non-skippers and 24.5% of the skippers), the majority in 2010 (n = 1551, 71.9% non-skippers, 71.6% skippers), and 106 in 2011 (5.0% non-skippers, 3.9% skippers).

Compared with children who were included in the main analysis, those not included were more likely to have skipped breakfast on the day of the face-to-face interview (2.8% versus 6.7%, respectively, Additional file 1: Table S1) and to have greater SES disadvantage, poorer teacher reported academic performance and behavior, and lower NAPLAN scores (Additional file 1: Table S1).

In this sample of Australian children, those who skipped breakfast aged 8-9 years tended to have poorer teacher-reported academic performance than non-skippers 2 years later. However objective standardized tests showed the differences were marginal, generally not statistically significant, and attenuated after adjusting for SES. Although a weakly significant difference between breakfast skippers and non-skippers was observed in one of the five NAPLAN scales (Numeracy, p = 0.04), the difference between the two groups was less than 3% and unlikely to be of great importance. Skipping breakfast was not associated with classroom behavior.

A meaningful difference for NAPLAN has not been defined. In the adjusted analysis, we found breakfast skippers had a 13-point lower score in the Year 5 numeracy test than non-skippers. Every year the national NAPLAN results are reported for each test, stratified by a variety of sociodemographic variables [20]. To put our observed difference into context, the national NAPLAN report showed a similar difference for sex, with the mean Year 5 numeracy score being 11 points higher among boys than girls [20]. Compared to children living in metropolitan areas, those from provincial areas had a 16-point lower numeracy score, and those from remote and very remote areas had a 31-33 point lower score [20]. Larger differences were observed in the national data for parent education, compared to those who had a parent with a university degree, mean Year 5 numeracy scores were 31 points lower among those whose parent had a diploma and 46 points lower among those whose parents had only completed year 12 [20].

This work builds on previous cross-sectional studies by examining the effect of skipping breakfast on academic performance 2 years later. National standardized tests gave an objective measure of academic performance, in addition to the teacher-reported outcomes. Data on skipping breakfast were collected over three non-consecutive days, allowing us to better capture intermittent skippers than would be possible with a single day’s measure. To reduce the possibility that skipping breakfast was due to feeling unwell, children were excluded from the analysis if they were reported to be ill on any of the days breakfast consumption was assessed using the time use diary. The large national sample is also a strength of this study.

There are several limitations that need to be considered. The proportion of children who skipped breakfast was low, with a very small number of children skipping breakfast on more than one occasion. Our results may not be generalizable to populations where children regularly go without breakfast. It is likely that skipping breakfast will increase in the LSAC cohort in adolescence for a range of psychosocial reasons and, with repeated follow-ups, different patterns of association may emerge. Stronger associations with academic performance may be observed in children who regularly skip breakfast. However, consistent skipping was very rare and intermittent skipping better reflects what was occurring in this age group. Breakfast data were collected over 3 days. While this allowed us to identify intermittent skippers better than would have been possible with data collected on just 1 day, this may still not fully reflect children’s usual breakfast habits. The children who usually skip breakfast one out of 3 days may go to school without breakfast one or 2 days each week but other children classified as skippers may go without breakfast less frequently. We were unable to examine change in breakfast habits in this analysis as breakfast consumption was not assessed at follow-up, and it is possible that children’s breakfast habits may have changed during the 2-year follow-up. Future research should examine whether becoming a breakfast skipper is associated with poorer performance on standardized tests or if becoming a breakfast eater is associated with improved standardized test results. Breakfast consumption was reported by parents and there is the possibility of misreporting due to social desirability bias. However, LSAC - a convenient data source to examine these hypotheses - did not have an overt focus on diet, reducing the likelihood of participants reporting socially desirable answers. It is recommended that parents report dietary intake for children up to 10 years of age to obtain reliable information [21]. We considered a range of potential confounders but there remains the possibility of residual confounding.

Our findings support those of Miller et al., who reported no significant differences between skippers and non-skippers in academic performance, assessed using standardized tests, or classroom behavior over 10 years among children from the USA [7]. In that study some children who ate breakfast may have been misclassified as breakfast skippers as breakfast was defined as eating breakfast with the family. To our knowledge, that is the only other study to examine the longer-term effect of skipping breakfast and it is reassuring to replicate the results in another country and a different education system.

There are several potential explanations as to why skipping breakfast was associated with poorer teacher-reported academic performance but not with the national standardized tests. Skipping breakfast was weakly associated with reading and numeracy in the national standardized tests but the associations were attenuated after adjusting for SES and other confounders. Residual confounding is a possible reason for the association between skipping breakfast and teacher-reported assessment, which was subjective and may have been influenced by other factors associated with skipping breakfast such as perceptions of the home environment and family support. This highlights the importance of using objective measures of academic performance. It is also possible that some children may perform differently in formal test situations than in other teacher-assessed classroom tests and assignments. The children were not all enrolled in the same year of school, therefore, the NAPLAN assessments were completed over 3 years. Reassuringly, the proportions of skippers and non-skippers who completed the NAPLAN tests during each year were very similar, so should not have affected the association between skipping breakfast and academic performance.

In Australia, the Government does not fund school food assistance programs, such as free or subsidized lunches. Some schools do have breakfast programs, which are often funded by non-Government organizations, such as the Red Cross and Foodbank Australia [22]. Program delivery such as frequency, foods provided and eligibility varies by school. It is not known whether children in this study participated in a school breakfast program. The breakfast question asked whether breakfast was consumed that day and should include breakfast consumed at home, school or other locations.

The prevalence of skipping breakfast was lower than in other international studies using national data [9, 10, 23] with only 10% of children skipping breakfast at least once. This could be explained by the young age of our cohort, as skipping breakfast has been shown to increase with age [9, 24] and previous studies included older children (aged 9-14 years old). It is difficult to compare studies due to the different age groups studied and methods used to define breakfast. However, the percentage of children who skipped breakfast is similar to national prevalence estimates from the 2011-12 Australian National Nutrition and Physical Activity Survey, where skipping breakfast was defined using two 24-h recalls [25]. In that study 8% of boys aged 4-8 years and 14% of boys aged 9-11 years skipped breakfast on at least one of the 2 days. Among girls 9% of 4-8 year olds and 14% of 9-11 year olds skipped breakfast on at least 1 day [25]. There is no consensus on the best method to assess breakfast. Short questions referring to breakfast consumption on the current day (as used here) are less prone to recall bias but may not capture usual eating patterns. Other studies have used a meal identified as breakfast in a 24-h recall [9]; eating or drinking something at home before school [10]; and eating within 2 hours of getting up [23].

Most studies only assess whether breakfast was eaten and rarely examine the quality of the breakfast. Further research is needed to determine whether certain breakfast types are more beneficial for cognitive performance. A recent systematic review, of studies conducted with children, adolescents and adults, reported there is emerging evidence that breakfast with a low postprandial glycemic response (produces a relatively small increase in blood glucose) has a beneficial effect on cognitive performance [26] but more well-designed studies are needed to determine the ideal breakfast composition. Further research is also needed to determine whether the association between skipping breakfast and academic performance differs by age and whether there are particular ages at which skipping breakfast has greater impacts on academic performance.

In this national sample of Australian children, few were skipping breakfast at 8-9 years of age. Breakfast skippers had poorer teacher-reported academic performance 2 years later than those who ate breakfast, but the differences in standardized national tests were small and attenuated after adjusting for SES. It is important to use objective measures of academic performance in further studies, otherwise false conclusions may drive unnecessary and costly interventions. The results from our study and well-designed randomized trials examining the effects of school breakfast programs on academic performance [4–6] suggest that, at a population level, public policy to provide breakfast to all elementary-school aged children may not result in improved education outcomes. However, our findings may not apply to populations with a high proportion of children who regularly go without breakfast.