Demographics of participants
The questionnaire surveys were conducted in 2015. First, for Chiba prefecture, a survey of 1,272 Yogo teachers was done at a Chiba prefecture Yogo teacher seminar in January. For the other prefectures, questionnaires were sent to the schools (614 in Hyogo in February, 492 in Ehime in February, and 1,301 in Saitama in June).
For Chiba, 661 responses were obtained (the effective response rate was 52.0 %). For Hyogo, 358 responses were received (58.3 %), Ehime had 362 (73.6 %) and Saitama had 503 (38.7 %). Combining these, the total sample size was 1,886.
G*POWER was used to verify the appropriateness of this sample size. By assuming the test method to be two-sided, the distribution to be normal, the significance level to be .05, the test power to be .80, and the odds ratio to be 1.3 in the logistic regression analysis, the required sample size was calculated to be 721. Moreover, the previous surveys of
Yogo teachers reported sample sizes of 150 [
18] and 391 [
19]. Therefore, we judged our sample size to be large enough.
Tables
1 and
2 show the basic statistics regarding the attributes of
Yogo teachers and their amount of ED knowledge. More than half (80.6 %) worked outside government-ordinance-designated cities (i.e., other areas) and about 19.4 % worked in government-ordinance-designated cities. More than half (56.0 %) worked at elementary schools, 28.6 % at junior high schools, 11.1 % at senior high schools, and 4.3 % at special needs schools. Of the schools, 26.3 % had 201–400 students, 20.5 % had 401–600, and 18.2 % had 61–200. About half (53.7 %) of the
Yogo teachers had 20 years or more of experience. Most (92.0 %) of them did not have nursing experience. Most of them reported that they “know roughly” about AN, BN and BED (70.7 %, 69.9 % and 55.5 %, respectively), while most reported that they “do not know well” about ARFID and Others (58.8 % and 58.9 %, respectively).
Table 1
Attributes of Yogo teachers (n = 1,886)
Location | Government Ordinance Designated City | 344 | 19.4 |
Other Area | 1428 | 80.6 |
Missing | 114 | - |
School Type | Elementary school | 1037 | 55.8 |
Junior high school | 529 | 28.4 |
Senior high school | 206 | 11.1 |
Special needs school | 80 | 4.3 |
Missing | 26 | - |
Number of Students | 1–60 | 160 | 8.7 |
61–200 | 333 | 18.2 |
201–400 | 481 | 26.3 |
401–600 | 375 | 20.5 |
601–800 | 236 | 12.9 |
801–1000 | 193 | 10.5 |
1001+ | 54 | 2.9 |
Missing | 54 | - |
Years of Experience | 1–5 | 335 | 18.0 |
6–10 | 227 | 12.2 |
11–20 | 299 | 16.1 |
20–38 | 999 | 53.7 |
Missing | 26 | - |
Nursing Experience | Experienced | 149 | 8.0 |
Not experienced | 1718 | 92.0 |
Missing | 19 | - |
Table 2
Amount of ED knowledge of Yogo teachers (n = 1,886)
Know well | 206 | 15.0 | 139 | 10.2 | 75 | 5.5 | 26 | 1.9 | 11 | 1.0 |
Know roughly | 968 | 70.7 | 955 | 69.9 | 755 | 55.5 | 325 | 23.9 | 165 | 15.0 |
Do not know well | 184 | 13.4 | 261 | 19.1 | 502 | 36.9 | 800 | 58.8 | 647 | 58.9 |
Do not know anything | 11 | 0.8 | 12 | 0.9 | 28 | 2.1 | 209 | 15.4 | 275 | 25.0 |
Missing | 517 | - | 519 | - | 526 | - | 526 | - | 788 | - |
Statistical Analysis 1: Encounter rates for each ED type
The order of the encounter rates for all four school types combined was AN > BN > ARFID > BED > Others. Therefore, the order of the encounter rates for seven- to 18-year-old students (in elementary/junior high/senior high/special needs schools) was believed to be the same. (Note that the order of BN and ARFID might be reversed because their confidence intervals overlapped (BN [0.129, 0.161], ARFID [0.115, 0.146]). In that case, the order would be AN > ARFID > BN > BED > Others).
In the comparison of our results with those of surveys done outside Japan, please note that although encounter and prevalence rates are different, no encounter rates are available from outside Japan, so we used the prevalence rate for comparison. American students aged 13–18 were interviewed face to face, and the order of prevalence rates was found to be BED > BN > AN [
24]. An English medical institute surveyed children aged 10–19, and the order was found to be EDNOS > AN > BN (EDNOS: Eating Disorder Not Otherwise Specified) [
20]. It was reported in a number of previous studies that the onset rates of EDNOS and BED in western Europe had increased in those years, while those of AN and BN in the United States and Europe had been constant or decreased since 1970 [
20,
22,
35].
In contrast, a survey of
Yogo teachers [
18] regarding high school girl students found the order of prevalence rates to be AN > EDNOS > BN. Although the survey methods of these studies were different from ours and we cannot definitively draw any conclusions, AN seems to be the most prevalent ED in Japan. Thus, it would be effective to provide support for AN patients here.
Statistical Analysis 2: Factors affecting the encounter rate (by ED type)
The first finding was that the factors affecting the encounter rates for all ED types were years of experience and knowledge of ED. The OR of years of experience ranged from 1.03–1.05, which means that the rate increases 1.03-1.05 times as the years of experience increase by one year. Although this result can be interpreted as “Yogo teachers enhance their skill in finding students with EDs as their experience increases,” a simpler explanation is also possible, that “the probability of encountering students with EDs increases as Yogo teachers work longer.” Actually, a survey of Yogo teachers who had worked at senior high schools for more than 10 years reported that the more their years of experience, the more various types of EDs they encountered.
Secondly, the relatively high ORs (2.59-4.23) implied that the amount of knowledge affected the encounters with students with an ED. It was also reported that the proportion of emaciation (extreme thinness) decreased after Yogo teachers were supplied with training on ED prevention. These facts imply that it is necessary to offer ED training in schools to improve the early support of students with EDs.
In particular, our results showed that the ORs of ARFID and Others were over 3.5. For ARFID, the ORs of all of the school types were not significant, which means that the encounter rates of all school types did not differ much and which coincided with studies reporting that ARFID is distributed among pre-puberty children as well as very young children [
36]. Thus, it can be concluded that it is necessary to educate
Yogo teachers about ED in all school types.
On the other hand, for Others, only the OR of special needs schools was significant. Some studies reported cases in which pica- and rumination-related obstacles (which were included in Others) co-existed with developmental disorders [
37,
38]. As special needs schools are schools for educating children with disorders, it makes sense that the encounter rate for Others is high in that school type. Thus, it can be inferred that it would be effective to support
Yogo teachers at special needs schools in their provision of early support for Others students.
Thirdly, the factor that did not affect the encounter rate was “nurse experience.” One survey of Yogo teachers with and without nursing licenses reported that personal effort contributed to the gathering and learning of ED information for both groups of teachers. These findings imply that nursing experience is not required to successfully provide early support for students with EDs.
For AN and ARFID, the ORs of schools in government-ordinance-designated cities ranged from 1.51–1.68, which means that the encounter rates were higher in government-ordinance-designated cities than in other areas. Because government-ordinance-designated cities can be roughly seen as urban areas and other areas as rural areas, this result was different from those of previous studies showing that the prevalence rates of urban and rural areas were almost the same [
17,
18,
24,
39‐
41]. The use of criteria based on DSM-5 rather than DSM-IV, which was used in the previous studies, might explain this discrepancy. For example, there could have been a considerable number of students with AN, BED, or ARFID who could not be classified into the corresponding categories because of the strictness of the classification criteria of DSM-IV, but because our criteria were based on DSM-5 such students were classified correctly, making our encounter rates higher.
For school type, the ORs of all ED types except ARFID were significant. The ORs of senior high schools (with students aged from 15–18) were high (6.56–15.2) for AN, BN, and BED (the ORs of BN and BED were over 10), which coincided with the results of previous studies. An English survey [
20] reported that the prevalence rates of 15- to 19-year-old children were higher than those of 10- to 14-year-old children for AN, BN, and EDNOS. An American survey [
24] also reported that the prevalence rates for BN of 15- to 16- and 17- to 18-year-old children were higher than that of 13- to 14-year-old children. These findings imply that it is necessary to support BN and BED in senior high schools. In comparison, the encounter rates in junior high schools were lower, but still significant (3.03-4.42). In particular, the OR of AN was high at 4.42, which implies that we should support AN beginning in junior high school.
For the number of students, only the OR of AN was significant at 1.001, which means that Yogo teachers at larger schools were more likely to encounter a student with AN. Generally speaking, teachers would be more likely to encounter various types of ED as the number of students increases. However, our results indicate that the number of students is not a significant predictor for any of the ED types except AN. The difference in the sample sizes may explain this, because the sample size of AN (850) was much bigger than those of ARFID and Others (246 and 102, respectively). The fact that the ORs of these three types were the same (1.001) also supports this explanation. (Note that the larger the sample size, the more likely it is that the OR becomes significant.)
These findings imply that it would be effective to offer ED knowledge to Yogo teachers mainly at school types with high encounter rates in order to enhance the early support of ED students.
Finally, we discuss the value of using DSM-5. In Japanese schools, a number of students have been reported to avoid school lunch, eat from their own lunch boxes, or eat their own hair (or things that are not considered edible). This suggests that ARFID and Pica are prevalent, and it would be effective to monitor the health condition of students based on the DSM-5 criteria. In fact, descriptions of students with ARFID or Pica were common in the free-writing section of our questionnaire, in all prefectures. Therefore, a questionnaire survey based on DSM-5 is believed to be appropriate for clarifying the actual ED situation in schools in order to assist Yogo teachers in their support of students with EDs.
Limitations and recommendations
One of limitations of our study is that a diagnosis by a
Yogo teacher may be less reliable than one by a doctor. Although we understand this limitation, we used the diagnosis by the
Yogo teachers for two reasons:
1)
In Japan, because doctors are allowed to enter schools for school health checkups just once a year, it is difficult for them to know the daily health condition of the students. In comparison, Yogo teachers stay in the schools and witness the health condition of students on a daily basis. Moreover, they are able to obtain information about students from other teachers or students. Thus, diagnosis by Yogo teachers may to some extent be more accurate than that by a doctor.
2)
Because Japanese students with EDs seldom go to medical institutions by themselves, Yogo teachers play an important role in finding them and supporting them. For this purpose, it is necessary to offer Yogo teachers information that is useful for supporting ED students, and the encounter rate is one such piece of information. Because our ultimate objective is to support Yogo teachers, we consider the subjective encounter rate to be more suitable than the objective prevalence rate, and we considered the encounter rates reported by Yogo teachers to be more suitable than those of doctors.
However, our choice created another limitation – a lack of prevalence rates. What we surveyed was the encounter rate and not the prevalence rate. That is, what we obtained was “the proportion of Yogo teachers who had encountered EDs” and not “the proportion of students with EDs.” For example, there are students with EDs who are not found by Yogo teachers because the teachers do not have sufficient knowledge or the students avoid visiting the offices of the Yogo teachers. Thus, the encounter rate differs from the prevalence rate.
The prevalence rate is also useful information, and should be determined in a future study by asking students directly if they have an ED. In such a study, information such as the age and sex of the students should also be obtained, as it could contribute to better support for Yogo teachers in their early assistance for students with EDs.
Other limitations include the questionnaire distribution methods. In our survey, the questionnaire was distributed by hand at a seminar hall or by mail. This difference in methods of distribution might have led to a difference in the degree of self-exposure to the questionnaire. A single survey method should be used in the future. In addition, our sample might be biased, as most of the surveys were collected from outside government-ordinance-designated city areas, which are usually rural areas. We will need to gather samples equally from inside and outside government-ordinance-designated cities in our future study.