Middle age is the time where most energetic activities are made in life, and the time where people are immersed in the family life and social activities actively and make efforts to live as a member of the society[1]. Middle age is a kind of transition period from adulthood to old age, and the middle aged are responsible for supporting their children their parents, and severely affected on their physical and mental health due to stress arisen from their additional roles[2]. Depression among them is an emotional disorder which represents anxiety, somnolence, sense of failure, sense of loss, feeling of helplessness and sense of worthlessness due to negative perception of oneself and causes disruptions in the daily life or accompanies several different types of symptoms or signs. Since more than half of middle aged women experience, it is reported depression is a majorhealth problem to women[3,4]. In addition, middle-aged men experience psychological anxiety, irritability, fatigue, and compassion on themselves and depression, often claim fatigue and resulting physical symptoms, while they experience physical changes as climacteric similar to menopausal symptoms in middle-aged women[5]. As the age increases, oral health decreases the due to oral diseases such as tooth loss, and the quantity and quality of the meals decrease due to narrowedchoice of food to cause nutritional imbalance and difficulties in maintenance of health[6]. Since oral health is the condition of teeth and the maxillofacial oral tissue that are not infected by diseases, not cause problems in mental functioning and social life, and are comfortable and functional teeth state to ensure the personal life may perform their social roles continuously[7], it has positioning as a main health evaluation item[8]. Although there are many studies on depression for the middle aged, there are not many studies related to the oral health and depression. Accordingly, the purpose of this study is to investigate the relationship between oral health related factors and depression in adults more than 40 and less than 60 years, who are classified as the middle-aged adults in Korea using the second year data of the 6th National Health and Nutrition Examination Survey in 2017.

The composition of this paper was written with the introduction of research subjects, research methods and research statistics methods for oral environment and depression. In the text, we looked at the relationship between the demographic factors of middle-aged adults and depression, checked the symptoms of depression in middle-aged adults, and analyzed the relationship between oral health factors and depression in middle-aged adults. The sequence of writing in this study was to use cross-sectional analysis to investigate the relationship between the demographic and depression of middle-aged adults, and the depression of middle-aged adults, and to analyze the frequency of depression in middle-aged adults.

In <Table 1> relationship between demographic factors and depression in middle-aged adults. To see the relationship between demographic factors and depression in middle-aged adults, 3.9% of women and 1.0% of men were diagnosed with depression by doctors and, for the marital status, 4.7% of married and, for the economic activity, 2.6% of active were diagnosed with depression. 1.9% of high school students and 4.3% of non-smoking were diagnosed with depression. Especially, for women, active in economic activities and the less educated, the higher depression (p <0.001).

In <Table 2> to see depressive symptoms of middle-aged adults, it was found 12.5% answered the continuous depression over 2 weeks, 4.9% answered that they were diagnosed with depression, and the time of depression diagnosis was 33.0% in 41-50 years old. 61.7% answered they have depression and 58.5% answered they are not treated with depression.

In <Table 3> to see the relationship between oral health factors and depression in middle-aged adults, the depression prevalence rate was found to be 2.8% when they recognize their oral health conditions are poor, 2.6% when they experienced toothache over the last year and, 4.7% when the experienced the permanent tooth caries respectively. When they have significant chewing problems, 1.4% was diagnosed with depression, and when they claim the chewing problems, 3.3% were diagnosed with depression. When they experienced toothache over the last year, have significant chewing problems or claim the chewing problems, it was found they have significant relationship with the prevalence rate of depression statistically.

This study was to investigate the relationship between oral health factors and depression in Korean middle-aged adults using data from the 6th National Health Survey (2013~2015). Studies have shown that the prevalence of depression in middle-aged adults is 4.9%, which is lower than the result of 22.2% in the study of Lee, et. al[9]. However, 12.5% of the respondents felt depressed for more than 2 weeks. In particular, considering 62.8% of the respondents were diagnosed with depression at 40~50 years of age, middle-aged adults do not feel the importance of health conditions or have not prepared for it. In addition, the middle age should take the responsibility of raising children and supporting their parents, and are stressed by various additional roles and seriously affected physically and mentally[10]. During economic activities, 2.6% were diagnosed with depression, and the stress of social life is considered to be the cause of depression. In this study, statistically significant results were obtained in the relationship between education level and depression, and it has been reported that education level is a major determinant in socioeconomic status because it directly or indirectly affects the health through various routes. In the study of Ross and Wu[11], depression was found to be low in the health conditions of the group with high level of education. It has been found that depression has a statistically significant relationship with oral health factors when they experienced toothache, have chewing problems, and claim mental discomfort during the last year. Oral health is closely related to health of the whole body and the problem in chewing deteriorates the chewing ability, narrows the scope of food selection and deteriorates the quantity and quality of foods for intake, which makes it difficult to maintain the health and physical strength[12]. In addition, oral health may affect pronunciation and appearance, and therefore, tooth loss or other masticatory discomforts can increase the prevalence of depression by promoting social isolation and alienation[13-15]. In other words, the oral discomfort factors are considered to increase the depression.

1. Middle-aged adults showed more depression when they were female, economically active, and less educated.

2. The time when depression was diagnosed is 41~60 years old (62.8%) applicable to the middle age and it was surveyed 58.5% did not take treatments after diagnosed as depressed.

3. In the relationship between oral health factors and depression in middle-aged adults, the prevalence of depression was high when they experienced toothache, chewing problems, and mental discomforts during the last year.

For the limitation of this study, 94 persons, the number of subjects with depression is very small and it is difficult to generalize the results. In addition, the National Health and Nutrition Survey is very difficult to find a causal relationship with the survey data. Nonetheless, it is significant to examine the relationship between oral-related factors and depression in middle-aged adults by using the National Health and Nutrition Survey. Since these results as above suggest that the oral health factors of middle-aged adults may affect depression, which may also negatively affect the quality of life, it is anticipated the measures to promote the motivation and interest in oral health of middle-aged adults may be prepared.