This study was approved by the Institutional Review Board of Teikyo University (approval number: 22-011-2). Participants’ selection of the item “Agree to participate” in the introductory statement of the questionnaire was considered as consent to participate in this study. The statement introduced this study and described that participation was voluntary, consent could be withdrawn at any time, data would be anonymized, and participants would be offered a ¥500 (US $3.30) Amazon gift voucher as compensation.

Parents of 1.5-year-old children who participated in the medical checkups provided at 3 health centers in Saku City, Nagano Prefecture, between May 11 and October 5, 2022, were recruited. The principal investigator (MS, a pediatrician) explained the study to each participant, and those who agreed to participate were included in this study.

Individuals were excluded if they were not the mother or father of the child or if they did not have a smartphone. The city staff collected the questionnaires.

The Oshiete-Doctor app, which was developed in 2016, is funded by Saku City and is provided free of charge to improve the home nursing skills of parents and guardians. It provides information on the following five topics: guidelines regarding hospital visits for children who are sick, explanations for child illnesses, information on vaccinations, information on childcare support groups, and disaster countermeasures for children. In Saku City, information regarding the app is distributed to all citizens when they register for birth certificates at the city office. The app is used throughout Japan and has been downloaded nearly 400,000 times.

We included sex, age, education status, self-rated economic status, current health care worker status, gestational weeks, birth weight, birth order, and past medical history of the children in our analysis. Education status was divided into 3 categories (high school graduate or lower, vocational school and 2-year college, and university graduate or higher) and then classified as “university graduate” or “non–university graduate.” With regard to self-rated economic status, participants reported their subjective economic status as “very good,” “good,” “fair,” “poor,” or “very poor.” Self-rated economic status was then classified as “very good - good,” “fair,” or “poor - very poor.” With regard to current health care worker status, participants who answered that they were health care workers were categorized as “yes,” whereas participants who answered that they were not health care workers were categorized as “no.” Gestation weeks were classified as either “<37 weeks” or “≥37 weeks.” Birth weights were classified as either “<2500 g” or “≥2500 g.” Birth order was divided into 4 categories (first, second, third, and fourth or more) and then classified as either “first child” or “second child or more.” With regard to the past medical history of the children, participants who answered that their children had any past medical history were categorized as “yes,” whereas participants who answered that their children did not have any past medical history were categorized as “no.”

Continuous variables were described as summary statistics (mean and SD or median and quartiles), while categorical variables were expressed as frequencies and percentages. The participants were divided into 2 groups based on their use of the Oshiete-Doctor app, and sociodemographic characteristics were compared by using the chi-square test or 2-tailed t test.

We also conducted univariable analyses (chi-square test or t test) and multivariable analyses (multiple logistic regression analyses) to examine the association between participant demographics and HLSs, as well as the association between emergency room visits and health care knowledge scores.

In the multivariable analysis, we included attributes of parents (sex, age, education, self-rated economic status, and health care professional status) and children (sex, birth order, and past medical history) as variables.

We included these variables because previous studies have shown that they may influence the association between pediatric emergency visits and parental health literacy [19-21]. A P value of <.05 was considered statistically significant. Stata 17 (StataCorp LLC) was used to analyze the data.

A flowchart of the survey is shown in Figure 1. A total of 251 respondents completed the survey (collection rate: 267/300, 89%; response rate: 251/267, 94%). Of them, 109 (43.4%) used the app. As shown in Table 1, 90.8% (228/251) of the respondents were female, 37.1% (93/251) had a university degree or higher, and 46.2% (116/251) of their children were firstborn. Overall, 20.3% (51/251) of the respondents were health care workers, and this proportion was significantly higher among app users than among non–app users (P=.005). No other participant or child attributes were significantly associated with app use.

Health care knowledge scores were examined in terms of app use (Table 2).

In the univariable analysis, the proportion of parents with higher health care knowledge scores was significantly higher among app users than among non–app users (P=.001), and the proportion of parents with higher scores regarding alcohol disinfection during gastroenteritis was significantly higher among app users than among non–app users (P=.02).

After adjusting for parent and child characteristics in the multivariable analysis, these differences remained statistically significant (P=.003 and P=.007, respectively).

The mean HLS of the participants was 24.2 (SD 7.3). The differences in the proportions of parents with higher health literacy, as measured with health care-related subscales of the HLS-EU-Q47, by app use, are shown in Table 3.

In the univariable analysis, the proportion of parents with higher total HLSs was significantly higher among app users than among app nonusers (P=.03), and the proportion of parents with higher HLSs for the evaluation subscale was significantly higher among app users than among app nonusers (P=.03).

After adjusting for parent and child characteristics in the multivariable analysis, the difference in the proportion of parents with higher total HLSs between app users and app nonusers remained statistically significant (P=.008).

In the univariable analysis of the association between a history of emergency room visits in the past 6 months and app use, emergency room visits were significantly more frequent among app users (26/102, 25.5%) than among non–app users (15/130, 11.5%; odds ratio [OR] 2.6, 95% CI 1.3-5.3; P=.007). This association was not significant in the multivariable analysis (parents included in analysis: n=216; adjusted OR 1.9, 95% CI 0.94-4.0; P=.07), in which the total HLS (a binary variable) was added to the adjusted variables (model 1).

This is the first study to examine the associations between the use of an app for parents that was developed in Japan and child-rearing parents’ health care knowledge, their health literacy, and emergency room visits for their children. The mean HLS of the participants was 24.2 (SD 7.3), which is similar to that in previous studies [16,22]. Recently, the internet has become an indispensable tool for gathering information, and mobile apps have played a significant role. Similarly, a greater number of maternal and child health interventions using mHealth technology have been observed in the field of maternal and child health [23], and mobile apps are used to support maternal and child health care interventions [24].

Our app provides knowledge about health care for children. A significant association was found between app use and accurate health care knowledge. Fadda et al [25] reported that their smartphone app intervention for parents increased parents’ knowledge of measles-mumps-rubella vaccination and parents’ psychological empowerment toward vaccinating their children. They demonstrated the effectiveness of interventions that use mobile devices to provide information. These findings are consistent with those of our study. However, in our study, there were no statistically significant differences between app users and app nonusers with high scores for the statement about visiting the emergency room at night if their child had a fever (P=.56) and the statement regarding their response to their child drowning (P=.25). This may be because these two statements were easy for most participants to answer correctly (correct answers for the statement about night fever: 226/249, 90.8%; correct answers for the statement about drowning: 233/249, 93.6%).

This study found a significant association between app use and parental health literacy. The measure of health literacy used in this study was designed to assess the subjective manageability of health-related tasks, focusing on both individuals and the underlying circumstances in which health-related tasks are performed [26]. The use of the Oshiete-Doctor app may lower the barriers to accessing, understanding, appraising, and applying health care information and thus result in the greater manageability of child health care.

Contrary to our expectations, we found a positive association between the use of the app and emergency room visits in the past 6 months. However, a systematic review reported an association between low parental health literacy and increased emergency room visit rates [27]. One possible reason for the contradictory result from the systematic review is that our study did not evaluate the appropriateness of emergency room visits. Although we hypothesized that the use of the app would reduce unnecessary emergency room visits, a higher emergency room visit rate may reflect more careful attention to the child and appropriate decisions based on the app. Another possibility is that the parents may have downloaded the app after experiencing an emergency room visit. In the region where this study was conducted, the app is widely known among health care professionals, who may have recommended the app to parents who visited the emergency room. Future studies are needed to evaluate the association between app use and emergency room visits.

There are several limitations to this study. First, the HLS-EU-Q47 has a limitation in its self-reporting formula. Therefore, the survey results may reflect the subjective manipulation of the participants and may not always correspond to the objective findings. However, it has been used for comparative studies in other countries, and there is also a Japanese version [16]; therefore, its reliability and validity have already been established, which is why it was chosen in our study. Second, this study was observational and could not rule out the influence of confounding environmental factors (except for the use of other apps) that could have contributed to the increase in parents’ health literacy. In addition, as this was a cross-sectional study, there is a possibility of causal reversal. Third, a high proportion of medical personnel was observed in this study (51/251, 20.3%). Nagano Prefecture, which includes Saku City, has more medical personnel per 100,000 people when compared to the national average. For example, the number of public health nurses per 100,000 people is 82.6, which is nearly double the national average (44.1 per 100,000 people) and makes Nagano Prefecture the region with the most public health nurses in the country [28]. Therefore, it may be difficult to apply our results to parents of 1.5-year-old children from other regions. However, this study exhibits small participant bias because it was conducted with participants of a municipal infant health examination. In Japan, health checkups are available for all infants, and the follow-up rate is very high. In addition, the collection rate was very high because of the full cooperation of the city. Therefore, the results are expected to accurately reflect the reality of parents raising infants and children in this region.

This study showed a significant association between parents’ use of a child health care information app and higher health literacy and health care knowledge. The use of the app may help parents increase their knowledge and ability to manage their children’s health by lowering barriers to accessing, understanding, evaluating, and applying health information. Future studies are needed to evaluate the impact of app use on health behaviors, including emergency room visits.