Introduction
Preventive orthodontics involves interventions and treatments that are undertaken in the primary or mixed dentition period with an intention to facilitate correct development of the occlusion and prevent the progression of malocclusion.1, 2 With a primary aim to ensure that all children have the support they need to grow up healthy, researchers, public health and public policy advocates have widened their search for possible factors that affect child health including development of malocclusion.
According to American Academy of Pediatrics (AAP), a quarter of children under the age of five don’t get adequate sleep. Indian children are among the most sleep-deprived in the world. On average, they barely clock eight hours of sleep a night instead of the prescribed 10–12 hours.3 This is worrying because poor sleep in the period of early childhood has been linked to many problems with the immune system, as well as anxiety and depression.4 Parents often sleep with their babies on the same bed or in same room in order to prevent these issues.5 Previous research has highlighted the beneficial impact of this practice on sleep improvement in babies.6 However, scientific literature is scarce regarding how the stopping of this practice may affect the oral health of the child and its possible role in the development of malocclusion. This study was undertaken to address the lack of information in the available literature about the different prevalent mother-baby sleeping arrangements in India and determine its possible role in the development of malocclusion.7
The null hypothesis of this study was that there is no difference in the occurrence of malocclusion among babies who shared the bed with their mothers or slept in a cradle in the same room and those who slept in a different room. The study aimed to investigate the possible association between the prevalent sleeping patterns among children in a mixed Indian population and the risk of development of malocclusion in these children. The objectives of the study were as follows:
Materials and Methods
Design and participants
Visakhapatnam, the largest city in the south Indian state of Andhra Pradesh was chosen for this cross-sectional study. The study was conducted over a period of 6 months, with a randomly selected sample of 2150 children from among pre-schools in the city. After obtaining permission from the educational authorities, the principal worker met with the teachers at the selected schools to inform them verbally and in writing of the aims and objectives of the study. The parents were informed about the study objectives and their written consent was obtained before proceeding with the study.
The Orthodontist obtained the data by planning school visits for carrying out free dental examinations for the children. Mothers were given a questionnaire to complete prior to dental examination of children. To avoid any bias, only one person monitored the total evaluation system. However, to ensure reproducibility and reliability of the index, the same orthodontist re-screened hundred children at an interval of 15 days.
Initially, 3258 mother–child dyads were screened for eligibility. From this group, 2150 children qualified as per eligibility criteria which was sufficient to provide a power of approximately 80% at 5% level of significance. Cluster sampling was performed. The following were inclusion criteria: children aged 2–6 years, children who were breastfed at night for at least six months and those born anytime between 37 weeks and 42 weeks to ensure a healthy sample. The exclusion criteria were as follows: children who did not co-operate, those with local/systemic diseases that could affect their oral health status and children who had initiated orthodontic treatment. Children who gave history of being bottle-fed before six months of age, those who received a mix of breastfeeding and bottle-feeding during first six months or were never breastfed at night were excluded. Parents who were mentally or physically disabled and those who submitted incomplete questionnaires were also excluded.
Analysis was carried out for the following parameters: duration and type of sleeping pattern (months), use of bottle, pacifier use, and digit sucking. When any of these habits was reported to be present, additional information which included frequency of the habit was recorded in hours/day, and length of its presence was expressed in months. Data on nail biting and thumb/finger sucking were collected by means of the questionnaire administered to the parents/ caregivers, and the habit of lip/tongue interposition was determined during the clinical examination. Tongue interposition was investigated by the observation of water swallowing and checking for tongue projection and the participation of the perioral musculature. Parents were also required to mention the duration of breastfeeding in months.
Procedures
Mouth mirrors, a millimetre scale, sterile gloves, and mouth masks, were used for the examination of children. The examination was carried out under bright day light in the school premises. Due to the inability of the traditional indices (like OI, IPION and ICON), to assess the need for orthodontic treatment in children, the Baby‑Risk of Malocclusion Assessment (ROMA) Index was used in this study and its suitability for utilisation in terms of ease of use and reliability was checked.8 This index is a modification of the ROMA Index and records the skeletal and functional aspects of malocclusions in mixed and permanent dentitions. Post validation of the ROMA Index, it was modified to the Baby‑ROMA index to evaluate the primary dentition. The Baby‑ROMA index has four groups - systemic, craniofacial, dental, and functional, and evaluates occlusal parameters and skeletal and functional factors (Table 1). Each group in this index has a number that marks the intensity and a letter of the alphabet that corelates to a type of malocclusion and brings out, in the form of a score scale, the need for interceptive orthodontic treatment. Anonymous data collection was employed, and all the collected data remained confidential. Guidelines of the index were used for coding the examined teeth for each participant and this was recorded in the applicable table according to the score of each code.
Statistical analysis
Statistical Package for Social Sciences (SPSS) version 22.0 was utilised for the data analyses. A t-test was performed on the descriptive analysis to determine if the dependent variables differed according to socio-demographic variables. χ2 or Pearson’s correlation established the relationships between variables depending on their type. Bonferroni test was used to measure the significance of post hoc comparisons. A two-way mixed-design ANCOVA (each habit and co-sleeping) was used for Baby ROMA Index, adjusted by covariates (rest of the habits). To estimate correlation coefficients between frequency and duration of sucking habits and malocclusion, Pearson’s correlation was used. Hierarchical regression analysis was used to determine the predictive capacity of the variables in the Baby ROMA Index. A statistical significance level of P < 0.05 was used to evaluate the results.
Table 1
Parameters assessed in the Baby ROMA index
Table 2
Characteristics of study participants (N=2150)
Table 3
M (SD) and significance for the variables for the different types of sleeping arrangements: mother-infant co-sleeping in same bed (Group 1, N= 1273), infant sleeping in the same room as the mother but not in the same bed (Group 2, N=632), and solitary sleeping in a different room (Group 3, N=245)
Table 4
Pearson’s correlation between Baby ROMA Score and pacifier use (duration and frequency)
Results
The distribution of 2150 children were 986 boys and 1164 girls. The participating children had a mean age of 4.34(±0.69) years, with a range of 2–6 years. The mothers’ age ranged from 24 to 39 years (M = 29.26 years, SD = 3.941). The data from parents revealed that 58.6% of them completed secondary education, 82.9% of the parents had a job, and 57.9% of the families belonged to middle or lower-middle class economic level (Table 2).
Duration of sleeping patterns and habits
From responses obtained, three prevalent mother-infant sleeping arrangements emerged: mother-infant co-sleeping on same bed (Group 1, N= 1273,59%), infant sleeping in same room as the mother but not in same bed (Group 2, N=632, 29%), and solitary sleeping in a different room(Group 3, N=245,12%). The influence of the sleeping pattern on the development of non-nutritive sucking habits and malocclusion was assessed.
Group 1 children slept with their mothers for a mean duration of 24.20(±5.02) months. These children reported exclusive breastfeeding for a period of 18.74(±3.12) months. 9.3% of these children used pacifiers, with a mean duration of use of 6.2(±1.21) months and a mean daily use of 6.12(±4.21) hours; a finger-sucking habit was seen in 6.4% with a mean age of 28.2(±4.72) months and with a mean daily duration of 2.75(±1.71) hours. In this group, 2.3% exhibited atypical swallowing, and 4.3% showed oral breathing. Based on average duration of sleeping together, Group 1 sample was divided into two sub-groups: Sub group 1- children sharing a bed for 18 months or less and Sub group 2-children sharing a bed for more than 18 months. Major differences in the duration of breastfeeding were found between these groups, with a mean (SD) of 13.47(±3.45) months for the group that slept together for 18 months or less and 19.94 (±3.81) months for children who shared a bed for more than 18 months. The children from Group 1 were shifted to either Group 2 or Group 3, when the child was sufficiently weaned away from breast feeding.
When the child and mother slept in the same room, children were found to share the same bed for a duration of 5.40(±2.10) months and exclusive breast feeding was reported for 9.60(±3.02) months. After a period of 16.20(±5.02) months, the children were shifted to a different room. For children who were reported to be sleeping in a different room, there was observed to be a duration of 6.45(±2.02) months when they shared the same bed or room as their mothers before they were made to sleep in a different room. In this group, the mean duration of exclusive nighttime breast feeding was 7.35(±1.2) months. In this group, mothers of infants consisted mainly of working women or those that had their own/spouse health issues. Whenever the infant slept in a different room, there was some form of baby monitor to keep a tab on the requirements of the infant. This type of arrangement was predominantly seen in the upper middle class and upper socio-economic group.
Analysis of the results reveals that appearance of harmful oral habits in children is closely related to the duration of mother and baby sharing the same room or bed. When the mother and child sleep together for 18 months or less, there was significantly higher frequency of pacifier use (X2(1) = 4.44, P = 0.035), finger sucking(X2(1) = 6.89, P = 0.009), and atypical swallowing(X2(1) = 5.00, P = 0.025) than the mother-baby group that slept together for more than 18 months. Daily usage of pacifier in the group where mother-baby sleep together for more than 18 months was found to be lower than other groups (pacifier; t = 2,194, P < 0.05; finger; t = 2,482, P < 0.05) (Table 3). Oral breathing was not found to be related to the duration of co-sleeping.
Sleeping pattern and appearance of malocclusion
It was noticed that when children slept in another room i.e. Group 3, they had higher mean Baby ROMA(t = 3,851, P < 0.01) scores compared to the other groups where mother and baby slept together on the same bed or same room (Table 3). In the two groups where mother and baby slept together on the same bed or in the same room, more malocclusion was seen in the group that co-slept on a different bed in the same room, which was statistically significant (t = 2, 531, P < 0.01).Other findings in children across all groups was observed to be dental caries (12.7%), followed by crossbite (7.6%). In Group 1, 3.6% (46) infants developed one type of malocclusion, while this number increased to 17.2% (108) in Group 2 and 46.8% (114) in Group 3 children. In children who slept alone and showed some type of malocclusion, 65.5%(74) needed monitoring and check‑up of occlusion before growth spurt, and 11.7%(14) needed immediate orthodontic treatment. Anterior open bites, posterior crossbites, canine Class II, deepbite/ overbite and overjet were found to be more in the group where mother and baby slept together for less than 18 months. Within Group 1 children, those that co-slept for less than 18 months were found to have higher incidence of anterior crossbite, but the numbers were insignificant. Utilising regression analysis, the duration and frequency of use of pacifiers were found to be significantly related to Baby ROMA scores (Table 4).
Discussion
From a review of literature, it emerges that this research is the first study in India to utilize observational data to assess the possible link between duration of mother-baby sleeping pattern and development of malocclusion. Another plus point for this study is that the study was conducted in a relatively large sample of mothers and children in a mixed Indian population in a cosmopolitan city of India.
Mothers and infants sleeping within proximity to each other (co-sleeping) represents normal, healthy, and expectable human behaviour, especially if mothers breastfeed.9 It has been established by previous research that mother and baby sleeping together plays an important part in promoting breastfeeding by increasing the duration of mother-baby contact, which in turn plays an significant role in the enhancement of emotional and cognitive abilities in the child. This is attributed to the release of oxytocin in human breast milk which results from sucking, touch, and warmth, reducing negative tendencies and enhancing social-emotional functioning in infants.10 A deep reading of available literature also indicates that exclusive breastfeeding may reduce the risk of children acquiring finger and pacifier habits due to reported connections between infant feeding practices and non-nutritive sucking habits (pacifier and finger sucking).11 Few other studies, however, could not establish any relation between sleeping pattern and the duration of breastfeeding.12 This study was able to demonstrate marked variations in the duration of exclusive breastfeeding between the three groups.
Children with an average age of 4.34 years and parents with a mean age of 32.26 years participated in this study. This study has been able to demonstrate interesting results regarding the prevailing varied mother-baby sleeping patterns in a cosmopolitan city of India encompassing various social and economic groups. The important finding of this study has been highlighting the massive benefits of mother and baby sleeping together on the same bed and that a period of at least 18 months is required for these benefits to have the intended positive influence. It was noted that the development of harmful sucking habits was significantly different in the three groups - varying with the period of mother-baby sleeping together on the same bed, with more harmful oral and non-beneficial habits being noted in the group with solitary sleeping arrangement. There are different opinions regarding the correct age for stopping mother and child sleeping together on the same bed. Few studies have opined that children may share the room with their parents for the first year at the most or a minimum period of first 6 months after birth. It has been noticed that after around 6 months of life, babies are likely to feel separation anxiety and so manifest specific signals that force parents to come to their aid.13 The parents when quizzed about the reasons for sleeping on the same bed for a longer duration with their child presented reasons such as individual preference, reduction of anxiety and facilitation of sleep for children, circumstances dictated by housing/financial considerations like limitation of space and not being able to buy a new/separate cradle. Infant care and breastfeeding convenience were also listed as reasons for mother-baby sleeping together for a longer period.
One novelty of this study is the new information obtained about children who slept lesser than 9 months with their parents, which was seen to contribute to a higher risk for development of malocclusion. This association has not been analysed till date. Few studies have analysed the link between breastfeeding, use of pacifiers, and digit sucking with problems in primary dentition.14 However, it is also important to note that a review of the literature on breastfeeding, use of bottle for feeding, and risk of developing malocclusion by Abreu et al. obtained inconclusive results.15
Results show significant differences between the three groups regarding malocclusion status with increased development of malocclusion in the group with solitary sleeping arrangement. Since p>0.05, statistically there was significant difference in distribution of malocclusion among males and females with females exhibiting more severe malocclusions than males. An important takeaway from this study is the reliability and utility of the Baby‑ROMA index for evaluation of early orthodontic treatment needs in milk teeth.
One limitation of this study is the possible role of heredity and presence of other harmful oral habits in the development of malocclusion which were not analysed in this study. Secondly, the applicability of this result to a wider population is to be considered with caution since a representative sample from a specific segment of the child population was considered. Another possible limitation is that since parents filled the questionnaire on their own, there exists a probability for memory bias and giving responses based on social desirability.
Conclusion
From this study, it can be safely deduced that when the mother and baby sleep together for more than the first 18 months after birth of the infant, it is associated with lower risk of development of malocclusion than sleeping together for a duration equal to or less than 18 months. In addition, it was observed that the duration of non-nutritive sucking habits (use of pacifiers and finger sucking), reduced whenever there was a longer duration of mother-baby sharing the same bed. All these results when put together in context are highly relevant since it suggests that the risk of developing malocclusion in Indian children reduces when the duration of mother and baby sleeping together increased beyond 18 months after birth.
Clinical significance
Orthodontists would be immensely benefitted with this knowledge about the prevalent sleep arrangements and practices and would be able to adequately counsel parents about the benefits of co-sleeping with the child on the same bed for atleast 18 months, to help reduce the development of malocclusion.
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