Introduction

It is not uncommon today for children to perform a number of tasks: domestic labor, sports, dance, music, computer classes or foreign language learning [1]. Family influences may stimulate the performance of these tasks, pressuring children to participate, or even demotivating them [1].

Children are expected to participate in family-care tasks [2-4]. The household tasks that children do are linked strongly to gender roles. Girls are asked to perform tasks inside the house, such as cleaning and cooking, while boys are expected to complete jobs outside the house, such as mowing the lawn and washing the car [5]. Girls devote more time to household labor than boys [4]. A study of schoolchildren in Ohio found that a higher percentage of boys participated in sporting activities, while the performing arts were a more common choice among girls [1].

Expectations of children's household work practices reflect other concepts, based on cultural values [3]. For example, cultures may differ in their expectations of when children should begin household work, and in the perceived value of children's work in the home [5]. Child labor is accepted in a number of cultures [3,6,7] and child slavery is even described in some societies [8].

For a child to be healthy, his or her emotional and physical health should be in harmony [9]. The family plays an important role in this harmony during infant development. The family influences the number and type of tasks performed by children. Anderson et al. [1] found that when children perceived that parents stimulated the performance of extracurricular tasks, they tended to be involved in a greater number of extra activities. Excessive involvement in tasks may lead the child to become overburdened. Overburdened children may become physically ill; therefore, there is a possible association between overburdening and disease [10].

Each child has different abilities. Not all children are capable of performing the same tasks [11]. Personality can also influence the performance of tasks [12]. Personality traits are related to individual ways of dealing with different situations [12-16]. Traits of neuroticism may result in reactions of anxiety and anger, whereas, responsibility/conscientiousness is expressed through self-discipline and a sense of duty [12-16]. Personality traits in childhood may also be observed in adulthood [17]. Depending on personality traits present during childhood, the individual may have difficulty dealing with pressure and conflict and subsequently suffer from stress [18]. Individuals who score highly for neuroticism tend to be emotionally hypersensitive, sensitive to ridicule, incapable of dealing with pressure, and panic easily in emergency situations [19,20]. Personality traits can also be associated with physical health such as nutritional disorders and sleep disturbance [18,19,21].

Bruxism is the habitual, involuntary grinding or clenching of the teeth [21-24]. This oral condition has a multifactor etiology that affects both children and adults [25-27]. Sleep bruxism is a type of sleep disorder [25,26]. Sleep plays an important role in children’s health [28,29]. The consequences of sleep bruxism include: muscle pain, headaches, tooth wear and tooth loss [27]. There are a number of theories that associate emotional factors to the triggering of sleep bruxism [14,18]. Individuals with stress and/or specific personality traits tend to release the tension accumulated during the day through sleep bruxism [14,18,21].

There is considerable discrepancy among the prevalence of bruxism (5.9% to 78%) [14,23-27]. A recent systematic review reported a range of 3.5% to 40.6% [28]. There are also divergences in data collection methods used to assess bruxism among children [26,30,31]. The difference in results among the various studies on bruxism in children demonstrates the need for further research on this subject [14,23,26,27,30]. An understanding of the factors that can initiate sleep bruxism is of paramount importance. Work on the prevention of damage caused by this condition at an early stage can lead to improvements in general health [21].

Studies of the association between children’s tasks and sleep bruxism were not found on the Pubmed and Scopus databases during a search performed in June 2013, using key-words: tasks, sleep bruxism and children. Therefore, it was considered important to study this association. Subsequently, the aim of the present study was to determine the association between children’s tasks, personality traits and sleep bruxism in Brazilian schoolchildren.

Materials and Methods

Results

As can be seen in Table 1, the majority of parents/guardians reported that they were living together (67.0%), while 214 (33.0%) were separated. The majority of families were classified as having low social vulnerability (61.3%), whereas, 38.7% were classified as being of high social vulnerability.

Regarding extracurricular activities, girls performed more household work (18.2%) than boys (15.4%). Girls performed more artistic activity (5.6%) compare to boys (2.2%) while sporting activities were most common among boys (27.6%) (see Table 1).

Sleep bruxism was present in 230 children (35.3%). However, as the majority of children without bruxism (66%) pertained to the group exposed to lesser social vulnerability as compared to the 34% with bruxism, an association was not found between vulnerability and bruxism (p = .390) (see Table 2). Moreover, the majority of children without bruxism (67.3%) had parents living together (p = .048) (Table 2). There was no statistically significant difference between gender and sleep bruxism, despite a higher percentage among girls (38.2%; p = .099) (Table 2).

The evaluation of the ratio between the residual deviance of the model (459.614) and degrees of freedom (649) in Poisson regression has shown a value lower but around 1. It indicates that there was no overidispersion of our data. Besides, our model fits well, considering that the chi-square test of residual deviance had shown a p value equal to 1.0. We then developed a negative binominal model. The value of the ratio between the residual deviance of this model (374.597) and degrees of freedom (651) was lower than in the Poisson regression with robust variance [39].

Regarding children involved in household work, bruxism and personality traits, an association between high neuroticism (p<.001; PR 0.62; 95% CI 0.49,0.78) and household work (p<.001; PR1 0.62; 95% CI 0.50,0.77) was found. In addition, sleep bruxism was more prevalent for the group of children with a high level of neuroticism (PR = 1.57; 95% CI 1.25,1.98) as well as for the group of children who performed household work (PR = 1.55; 95% CI 1.25,1.91) (see Table 3).

Discussion

The present study evaluated the association between sleep bruxism, personality and tasks performed by children. To test the association, parents were requested to complete a questionnaire regarding prevalence of bruxism, characteristics of their children, and the types of tasks that they performed at home. The personality traits of children were also measured. Several points of interest were found.

First, no significant difference was found between genders regarding sleep bruxism. This result is in contrast to the study conducted by Lam, Zhang, Li and Wing [26] who found a greater prevalence of sleep bruxism among boys. However, differences were found between genders regarding type of tasks performed. The majority of girls performed household work and arts, which is similar to the findings found by Arends-Tóth and Van de Vijver [5], while sporting activities were more common among boys.

Secondly, household work is still identified as a largely female activity. The present study found that Brazilian families continue to sustain the culture of a division of tasks among their members. This tendency of family behavior has been noted in other studies [3,4,10]. The participation of the child in domestic tasks is seen as part of the educational process and stimulates discipline in childhood [10]. However, the child may be under stress if there is strong familial pressure involved in the performance of his or her tasks [1]. It is known that high stress levels are associated with sleep bruxism [18,29]. Thus, it is not surprising to find in the present study that the majority of children who performed work at home were those who suffered from sleep bruxism.

Thirdly, it was found that the majority of children without sleep bruxism had parents who lived together. Whether or not harmony at home affects the emotions of children is still a controversial subject [2,4,40].

Fourthly, children with high Neuroticism scores were more prone to sleep bruxism. If Neuroticism is characterized by the susceptibility to negative emotions which affect the adaptive functioning of an individual [19,20,37], household tasks could increase irritability among children with high Neuroticism [3,4]. On the other hand, pleasurable activities would have a positive influence on the quality of sleep [29,41,42]. Coincidently, in the present study, the majority of children who played some kind of sport did not suffer from sleep bruxism. This pleasurable sensation may be a protective factor for diminishing high levels of Neuroticism and sleep bruxism.

Despite these findings, some limitations of the present study should be stated. For instance, the survey of types of tasks performed by children was based on information provided by parents. As a result, the non-evaluation of information from the children themselves about the type and quantity of work, and the feelings of pleasure or displeasure in performing the tasks, was a limitation of the present study. However, it is worth noting that studies regarding sleep bruxism and children’s tasks were not found in the Pubmed and Scopus databases in a search performed in June 2013. Thus, further investigation is necessary, especially in developing countries, in which household work performed by children is a common social phenomenon.

Conclusion

Based on the results of the present study, the following conclusions can be made:

1. 1. Family characteristics and social behaviour can affect the emotional development of children.
2. 2. Emotional aspects must be considered when investigating the presence of sleep bruxism in children.
3. 3. Personality traits and children’s tasks are important factors that influence sleep bruxism among children.
4. 4. The results of this investigation should advise health professionals of the importance of detailed interviews with families.