Introduction

The Health Behaviour in School-aged Children (HBSC) study was an international survey on adolescent health. The main aim of this study was, understanding smoking behaviours in adolescents in three countries, which soon were expanded to determine adolescents’ health and health behaviours in 47 countries [1]. Subjective Health Complaints (SHC) involve the physical, emotional, mental, social and behavioural components of well-being, and functioning as perceived by the individual [2,3,4]. A research study in 19 countries in Europe and in the USA revealed that health complaints such as: headache, stomachache, difficulties in getting to sleep, and nervousness were common among adolescents [5]. It has been shown that 44% of school children have multiple recurrent health complaints in 41 European and North-American countries [6]. SHC without objective signs or symptoms can play an important role in short term sickness absence in adolescents. Almost half of the days lost due to sickness absence are due to diagnoses that mostly depend on subjective statements from the patient [7].

Meal skipping is more evident among young adults and adolescents who frequently fail to consume regular meals [8]. A meta-analysis of 24 studies conducted in Iran revealed that the prevalence of breakfast skipping was 21%; with higher percentage for girls compared to boys (26 vs 18%) [9]. The prevalence of breakfast, lunch and dinner skipping in Iranian adolescents were reported to be 32.1, 8.9 and 10.9%, respectively [10]. These unhealthy dietary behaviours may play a role in increasing future risk of chronic diseases [11]. It has been demonstrated that habits pertaining to breakfast consumption are significantly associated with all health status dimensions (physiological, psychological and social) [12]. A population-based study in Italy showed a positive association between headache and meal skipping especially irregular intake of breakfast [13].

Although previous studies have shown an association between breakfast skipping and some physical and/or psychological complaints, none to our knowledge have examined the possible influence of meal frequency on the cluster of somatic and psychological complaints, therefore, the purpose of this study is to investigate the association between meal skipping and subjective health complaints in children and adolescents in Iran.

Materials and methods

Study design and participants

The data of this cross-sectional study were collected as a part of the “National survey of school student high risk behaviours” (2014–2015), the fifth survey of Childhood and Adolescence Surveillance and Prevention of Adult Noncommunicable disease (CASPIAN)-V study. Details of protocol of the study have been described elsewhere [14]. Briefly, the study population was students aged 7–18 years in primary and secondary schools in urban and rural areas of Iran. A total of 14,400 students were selected using multistage, stratified cluster sampling method from 30 provinces nationwide. The main aim of this national school-based study was identification of health risk behaviours and risk factors of chronic diseases. The students’ questionnaire was derived from the World Health Organization-Global School Student Health Survey (WHO-GSHS) [15]. The validity and reliability of Farsi-translated questionnaire was assessed previously. Cronbach’s alpha coefficient of this questionnaire was 0.97, and the Pearson’s correlation coefficient of the test–retest phase was 0.94 [16]. Eligible students, who had Iranian nationality, did not have any chronic conditions and did not use any medication, were identified and interviewed. The provided information was about their lifestyle, health status, health-related behaviours and health complaints.

Study protocols were approved by the Ethics committee of Isfahan University of Medical Sciences, Project number: 194049. After complete explanation of the study objectives and protocols, written and verbal informed consent was obtained from the parents and students, respectively.

Dietary assessment

Students were asked if they eat breakfast, lunch and dinner during a week and weekends. To assess weekday breakfast, lunch and dinner consumption; adolescents were asked to indicate how many days in a week they had three main meals (defined as ‘more than a glass of milk or fruit juice’ and a snack like a biscuit). There were eight response categories: ‘never’, ‘1 day’, ‘2 days’, ‘3 days’, ‘4 days’ and ‘5 days’, ‘6 days’ and ‘7 days’. The responses were dichotomized into ‘three-meal consumption more than 5 days a week’ versus ‘less than four times a week’ which the latter was considered as “meal skipper”. This cut-off point was chosen according to statistical analysis when subjects used less than 50% of median.

Anthropometric and physical activity measures

A team of trained health care experts implemented the physical examinations under standard protocols using calibrated instruments [16, 17].

To assess screen time, the students were asked to report the average number of hours per day spent watching TV, playing video or PC games on week days and at weekends. Then, the total cumulative time spent on screen time was estimated and categorized into two groups of low screen time (less than 2 h a day) and high screen time (equal or more than 2 h a day) [18, 19]. We used the physical activity questionnaire for adolescents (PAQ-A) to assess their physical activity levels. The 7-day physical activity recalls were collected through a self-administrated questionnaire [20, 21]. The validity and reliability of this questionnaire were assessed in Iranian population. Cronbach’s alpha coefficient of the whole questionnaire was 0.97, and the Pearson’s correlation coefficient of the test–retest phase was 0.94 [22].

Subjective health complaints (SHC)

Data were collected using a self-completion questionnaire, administered by public health experts, which was designed as part of the WHO–HBSC study involving researchers from all countries. SHC were assessed by asking children to report the frequency, in the 6 months before the survey, of experiencing a variety of psychological (feeling low, irritability, feeling nervous, difficulty in getting to sleep) and somatic symptoms (headache, stomach ache, backache, feeling dizzy). Items within the scale have shown an adequate content validity and reliability. Response options for each items were ‘about every day’, ‘more than once a week’, ‘about every week’, ‘about every month’ and ‘rarely or never’. They were dichotomized as “weekly or more” versus “rarely or never” [23].

Statistical analysis

Categorical and continuous variables were expressed as number (percentage) and mean (standard deviation), respectively. Characteristics of participants according to their age groups were demonstrated using Pearson’s Chi-square test. Prevalence of reporting SHC in relation to meal skipping was also shown using Pearson’s Chi-square test. We used Benjamini–Hochberg procedure to get adjusted P value correcting for bias inherent in multiple-comparison testing [24].

We assessed the relationship between meal skipping and SHC using three separate logistic regression models. Covariates such as age, sex, socioeconomic status (SES), regions, physical activity, and screen time were adjusted in these models. Statistical analysis was performed using STATA software version 11. P value less than 0.05 was considered as statistically significant.

Results

Overall, 14,274 students (out of 14,440) completed the survey (participation rate: 99%). Fifty-one percent of adolescents aged 7–12 was girl, while 52.2% of adolescents aged 13–18 was boy. The mean age of participants was 12.5 years. 78.8% of adolescents aged 13–18 lived in urban areas. 85.1% of participants aged 7–12 had less than 2 h of screen time. Breakfast skipping was more prevalent in those aged 13–18 (P = 0.05). While, lunch and dinner skipping were 5.9 and 6.6% in 7–12 years old (P < 0.0001), respectively. SHC were prevalent in adolescents aged 13–18 (P < 0.0001) (Table 1).

Table 1 Characteristics of participants of study population: the CASPIAN-V study (n = 14,194)
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Table 2 shows that the prevalence of headache and difficulties in getting to sleep was significantly higher among those who skipped three main meals. In addition, the prevalence of experiencing all psychological complaints was higher among dinner skippers (P < 0.0001).

Table 2 Prevalence of reporting subjective health complaints in relation to meal skipping in Iranian adolescents: the CASPIAN-V study (n = 14,091)
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Table 3 indicates that breakfast skipping was associated with increased odds of stomachache (OR 1.77, 95% CI 1.56, 2.00), backache (OR 1.68, 95% CI 1.46, 1.92), difficulty in getting to sleep (OR 1.66, 95% CI 1.48, 1.86), feeling nervous (OR 1.59, 95% CI 1.43, 1.76) and irritability (OR 1.29, 95% CI 1.02, 1.25). There were 27, 63, 58 and 107% increase in odds of headache, stomachache, backache, and difficulty in getting to sleep by skipping lunch, respectively. While skipping dinner was related to increased odds of headache (OR 2.398, 95% CI 2.08, 2.77), feeling low (OR 2.59, 95% CI 2.19, 3.06) and difficulty in getting to sleep (OR 1.52, 95% CI 1.30, 1.18), it was associated with decreased odds of stomachache (OR 0.33, 95% CI 0.25, 0.44) and feeling dizzy (OR 0.52, 95% CI 0.38, 0.72), respectively.

Table 3 Association between meal skipping and health complaints in participants of the CASPIAN-V study (n = 12,311)
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Discussion

To the best of our knowledge the current study is the first national study in developing countries that has investigated the association of meal skipping with SHC. It is worth noting that this population-based study conducted among 14,400 students aged 7–18 years from 30 provinces of Iran.

The Iranian eating habits (in terms of meal sizes and timing) would be generally close to Mediterranean; a standard simple breakfast, a large lunch and a light dinner with desserts or fruits as snack or before bed. Although, dietary habits of different parts of Iran are quite varied, studies have shown that middle school Iranian students are more likely to consume animal fat diet characterized by high intake of whole fat dairy products, animal fat, and organ meat, while high school students compared to middle school students have a strong interest toward lower fat intake, especially saturated fat, and higher consumption of vegetables and fruits [25].

Findings of our study indicate that irregular breakfast, lunch and dinner eating is associated with myriad psychological and somatic symptoms. Studies have shown that consuming three meals a day plays a significant role in providing daily nutrient recommendation for macronutrients and micronutrients and skipping meals can deprive our body from the main source of nutrients [26] and subsequently leads in experiencing adverse health outcomes [27].

In the current study, skipping breakfast was related to psychological symptoms which is in line with a study carried out in Japan. In this study, skipping breakfast was associated with poor feeling and overall health in children [28]. A research study conducted in Iran revealed that adolescents who followed meal skipping eating pattern were more likely to experience emotional disorders [29]. A national survey in Taiwan also demonstrated that breakfast skipping was linked to lower score in mental health, emotional role, social functioning and general health perception domain scores [30]. The KNHANES, a population based study in 2010–2012 showed that breakfast and dinner skippers had more physical and mental problems such as stress perception and irregular menstruation [31].

The association between meal skipping and some somatic symptoms like stomachache, reflux [32] and, the most prevalent complaints, headache has been reported [33]. Our findings confirmed the results of previous studies in Italy, which showed a positive association between headache and meal skipping [13]. One of the possible mechanism for this finding could be hypoglycemia [34]. In the current study skipping meals was related to backache and stomachache, however, skipping dinner was a protective factor for stomachache. It has been documented that irregular meal timing is correlated with increased acidity, gastric reflux, and eventually stomachache [35]. Regarding the protective effects of dinner on stomachache, it is possible that children consume a heavy meal at dinner or there might be short dinner-to-bed time which is associated with gastro-esophageal reflux and other related symptoms [36].

One of the main limitations of our study is the cross-sectional design by which causality cannot be inferred. Although, the quality of meals is an important component in the complex interaction between lifestyle factors and overall health in early adolescence, we focused on the association of meal frequency with SHC and did not assess the quality of meals, therefore, we believe that this should be investigated through further research studies. Another limitation of current study was lack of knowledge about nutritional status of our subjects, hence we could not show the effects of this factor on SHC.

The main advantages of our study are its large sample size at national level, which ensures the representativeness of our participants and providing the possibility of generalizing our findings to other similar populations and a high-quality control of data collection.

In conclusion, meal skipping is related to SHC in Iranian children and adolescents. Therefore, promoting regular meal timing as consuming three meals a day should be highly encouraged in this population.