Age-related Changes of Lip-closing Strength and Related Factors in Elementary School Children

Abstract

 This study aimed to examine trends in lip-closing strength (LCS) and the influence of related factors in elementary school children. The study population consisted of 328 elementary school children (first to sixth graders; 167 boys and 161 girls) in Niigata Prefecture, Japan. We measured the children’s LCS with a digital force gauge (Lipplekun^®), and children and their parents completed a 10-item questionnaire (response rate= 80.8%). In order to show the trends of LCS in elementary school children, those trends according to age were compared. Furthermore, the subjects were divided into two groups according to age: under 9 years old and over 9 years old. The characteristics of the subjects according to the LCS quartiles in each group were compared, and relationships were also examined. The results showed that LCS of the subjects in this study increased slowly with age. In the group under 9 years old, the characteristics associated with LCS quartiles were the number of present teeth and snoring (odds ratio [95% confidence interval] = 1.28[1.01-1.56] and 0.45[0.24-0.84], respectively). In the group over 9 years old, the characteristics associated with LCS quartiles were the age and rohrer index (1.45 [1.09-1.93] and 6.02[2.21-16.39], respectively).

 In this study, the influence of LCS-related factors in elementary school children was considered to change around the age of 9 years old. These study results indicate that the factors increasing LCS were the number of present teeth in the group under 9 years old, and the age and rohrer index in the group over 9 years old. Also, these study results indicate that a factor decreasing LCS was snoring in the group under 9 years old.